1. Classes, Methods and Schema

This reference guide lists and describes various elements of the the Apache Isis Programming Model, specifically reserved and prefix methods (such as title() and validate…()) and various utility and supporting classes.

It also describes the XSD schema defined by Apache Isis. One use case is for the JAXB serialization of view models.

1.1. Other Guides

Apache Isis documentation is broken out into a number of user, reference and "supporting procedures" guides.

The user guides available are:

The reference guides are:

Annotations
Domain Services
Configuration Properties
Classes, Methods and Schema (this guide)
Apache Isis Maven plugin
Framework Internal Services

The remaining guides are:

Developers' Guide (how to set up a development environment for Apache Isis and contribute back to the project)
Committers' Guide (release procedures and related practices)

2. Methods

The Apache Isis metamodel is built up from declaratively (ie, annotations) and imperatively, from "supporting" methods and other reserved methods.

This chapter documents the supporting methods and the reserved methods. It also documents (separately) the reserved methods that act as callback hooks into the persistence lifecycle of domain entities.

2.1. Supporting Method Prefixes

Supporting methods are those that are associated with properties, collections and actions, providing additional imperative business rule checking and behaviour to be performed when the user interacts with those object members.

This association is performed by name matching. Thus, a property called "firstName", derived from a method getFirstName() may have supporting methods hideFirstName(), disableFirstName() and validateFirstName(). Supporting methods are, therefore, each characterized by their own particular prefix.

Using name matching to associate supporting methods generally works very well, but of course if an object member’s method is renamed, there’s always the risk that the developer forgets to rename the supporting method; the supporting methods become "orphaned".

Apache Isis checks for this automatically, and will fail-fast (fail to boot) if any orphaned methods are located. A suitable error message is logged so that the issue can be easily diagnosed.

The table below lists the method prefixes that are recognized as part of Apache Isis' default programming model.

Prefix Object Property Collection Action Action
Param Description

addTo…()

Y

add object to a collection

Directly mutable collections are not currently supported by the Wicket viewer.

2.1.1. `addTo…()` (deprecated)

The addTo…() supporting method is called whenever an object is added to a collection. Its purpose is to allow additional business logic to be performed.

Directly mutable collections are not currently supported by the Wicket viewer. The suggested workaround is to simply define an action.

For example:

public class LibraryMember {
    public SortedSet<Book> getBorrowed() { ... }
    public void setBorrowed(SortedSet<Book> borrowed) { ... }
    public void addToBorrowed(Book book) {
        getBorrowed().add(book);                                              (1)
        reminderService.addReminder(this, book, clock.today().plusDays(21));  (2)
    }
    public void removeFromBorrowed(Book book) { ... }
    ...
}

1	update the collection
2	perform some additional business logic

2.1.2. `autoComplete…()`

The autoComplete…() supporting method is called for action parameters and for properties to find objects from a drop-down list box. The use case is when the number of candidate objects is expected to be large, so the user is required to enter some characters to narrow the search down.

If the number of candidate objects is comparatively small, then use choices…() supporting method instead.

The signature of the supporting method depends on whether it is for a parameter or a property.

Parameters

For an action parameter in (0-based) position N, and of type T, the signature is:

public List<T> autoCompleteNXxx(String search) { ... }

It is also valid to return T[], a Set<T> or a Collection<T>.

For example:

public class ShoppingCartItem {
    @Property(editing=Editing.DISABLED)
    public Product getProduct() { ... }
    public void setProduct(Product product) { ... }

    @Property(editing=Editing.DISABLED)
    public int getQuantity() { ... }
    public void setQuantity(int quantity) { ... }

    @Action(semantics=SemanticsOf.IDEMPOTENT)
    public ShoppingCartItem updateProduct(
        Product product,
        @ParameterLayout(named="Quantity")
        final int quantity) {
        setProduct(product);
        setQuantity(quantity);
    }
    public Collection<Product> autoComplete0UpdateProduct(  (1)
        @MinLength(3) String search                         (2)
    ) {
        ...
    }
    ...
}

1	`product` is the 0th argument of the action.
2	the `@MinLength` annotation specifies the minimum number of characters that must be entered before a search is performed for matching objects

Properties

For a property of type T, the signature is:

public List<T> autoCompleteXxx(String search) { ... }

(As for action parameters) it is also valid to return T[], a Set<T> or a Collection<T>.

For example:

public class ShoppingCartItem {
    public Product getProduct() { ... }
    public void setProduct(Product product) { ... }

    public Collection<Product> autoCompleteProduct(
        @MinLength(3) String search                     (1)
    ) {
        ...
    }
    ...
}

1	the `@MinLength` annotation specifies the minimum number of characters that must be entered before a search is performed for matching objects

2.1.3. `choices…()`

The choices…() supporting method is called for both action parameters and for properties, to find objects from a drop-down list box. Unlike autoComplete…(), the use case is when the number of objects is comparatively small and can be selected from a drop-down without any additional filtering.

The signature of the supporting method depends on whether it is for an action parameter or a property.

Parameters

For an action parameter in (0-based) position N, and of type T, the signature is:

public Collection<T> choicesNXxx() { ... }

For example:

public class ShoppingCartItem {
    @Property(editing=Editing.DISABLED)
    public Product getProduct() { ... }
    public void setProduct(Product product) { ... }

    @Property(editing=Editing.DISABLED)
    public int getQuantity() { ... }
    public void setQuantity(int quantity) { ... }

    @Action(semantics=SemanticsOf.IDEMPOTENT)
    public ShoppingCartItem updateProduct(
        Product product,
        @ParameterLayout(named="Quantity")
        final Integer quantity) {
        setProduct(product);
        setQuantity(quantity);
    }
    public Collection<Integer> choices1UpdateProduct() {
        return Arrays.asList(1,2,3,5,10,25,50,100);
    }
    ...
}

Dependent Choices

Action parameters also support the notion of dependent choices, whereby the list of choices is dependent upon the value of some other argument.

An example can be found in the (non-ASF) Isis addons' todoapp, whereby `ToDoItem`s are categorized and then can also be subcategorized:

This functionality is actually implemented as a contributed action, so the code for this is:

@DomainService(nature = NatureOfService.VIEW_CONTRIBUTIONS_ONLY)
public class UpdateCategoryContributions ... {
    @ActionLayout(
            describedAs = "Update category and subcategory"
    )
    @Action(semantics = SemanticsOf.IDEMPOTENT)
    public Categorized updateCategory(
            final Categorized item,                              (1)
            final Category category,
            @Parameter(optionality = Optionality.OPTIONAL)
            final Subcategory subcategory) {
        item.setCategory(category);
        item.setSubcategory(subcategory);
        return item;
    }
    public List<Subcategory> choices2UpdateCategory(             (2)
            final Categorized item,                              (3)
            final Category category) {                           (4)
        return Subcategory.listFor(category);
    }
    ...
}

1	`ToDoItem` implements `Categorized`
2	subcategory is the 2-th argument (0-based)
3	the item contributed to
4	the category selected

Dependent choices are not restricted to enums, however. Going back to the shopping cart example shown above, the choices for the quantity parameter could be dependent upon the selected Product:

public class ShoppingCartItem {
    ...
    @Action(semantics=SemanticsOf.IDEMPOTENT)
    public ShoppingCartItem updateProduct(
        Product product,
        @ParameterLayout(named="Quantity")
        final Integer quantity) {
        setProduct(product);
        setQuantity(quantity);
    }
    public Collection<Integer> choices1UpdateProduct(Product product) {
        return productService.quantityChoicesFor(product);                 (1)
    }
    ...
}

1	`productService` is a (fictitous) injected service that knows what the quantity choices should be for any given product

Properties

For a property of type T, the signature is:

public Collection<T> choicesXxx() { ... }

For example:

public class ShoppingCartItem {
    public Product getProduct() { ... }
    public void setProduct(Product product) { ... }

    public Collection<Product> choicesProduct() {
        ...
    }

2.1.4. `clear…()` (deprecated)

The clear…() supporting method is called — instead of the setter — whenever an (optional) property is to be set to null. Its purpose is to allow additional business logic to be performed.

DataNucleus' smart handling of setters means that this supporting methods are in essence redundant, and so should be considered deprecated.

For example:

public class LibraryMember {
    public Title getFavoriteTitle() { ... }
    public void setFavoriteTitle(Title title) { ... }
    public void modifyFavoriteTitle(Title title) { ... }
    public void clearFavoriteTitle() {
        if(getTitle() == null) { return; }
        setFavoriteTitle(null);                         (1)
        titleFavoritesService.decrement(title);         (2)
    }
    ...
}

1	update the property
2	perform some additional business logic

2.1.5. `default…()`

The default…() supporting method is called for action parameters to return the initial argument value. This may be some sensible default (eg today’s date, or 0 or 1), or — for an action that is modifying the state of an object — might default to the current value of a corresponding property.

The method is also called for properties in the case when an object is newly instantiated using DomainObjectContainer#newTransientInstance(…). This is a much less common use case. If a default is not specified then properties are initialized to a default based on their type (eg 0 or false).

The signature of the supporting method depends on whether it is for an action parameter or a property.

Parameters

For an action parameter in (0-based position n), and of type T, the signature is:

public T defaultNXxx() { ... }

For example:

public class ShoppingCartItem {
    @Property(editing=Editing.DISABLED)
    public Product getProduct() { ... }
    public void setProduct(Product product) { ... }

    @Property(editing=Editing.DISABLED)
    public int getQuantity() { ... }
    public void setQuantity(int quantity) { ... }

    @Action(semantics=SemanticsOf.IDEMPOTENT)
    public ShoppingCartItem updateProduct(
        Product product,
        @ParameterLayout(named="Quantity")
        final Integer quantity) {
        setProduct(product);
        setQuantity(quantity);
    }
    public Product default0UpdateProduct() {    (1)
        return getProduct();
    }
    public int default1UpdateProduct() {        (2)
        return getQuantity();
    }
    ...
}

1	default the 0-th parameter using the current value of the `product` property
2	default the 1-th parameter using the current value of the `quantity` property

Defaults are also supported (of course) for contributed actions. For example, here is a contributed action for updating category/subcategory of the (non-ASF) Isis addons' todoapp:

@DomainService(nature = NatureOfService.VIEW_CONTRIBUTIONS_ONLY)
public class UpdateCategoryContributions ... {
    @ActionLayout(
            describedAs = "Update category and subcategory"
    )
    @Action(semantics = SemanticsOf.IDEMPOTENT)
    public Categorized updateCategory(
            final Categorized item,                              (1)
            final Category category,
            @Parameter(optionality = Optionality.OPTIONAL)
            final Subcategory subcategory) {
        item.setCategory(category);
        item.setSubcategory(subcategory);
        return item;
    }
    public Category default1UpdateCategory(                     (2)
            final Categorized item) {
        return item != null? item.getCategory(): null;
    }
    public Subcategory default2UpdateCategory(                  (3)
            final Categorized item) {
        return item != null? item.getSubcategory(): null;
    }
}

1	`ToDoItem` implements `Categorized`
2	defaults the 1-th parameter using the item’s `category` property
3	defaults the 2-th parameter using the item’s `subcategory` property

Properties

For a property of type T, the signature is:

public T defaultXxx() { ... }

For example:

public class ShoppingCartItem {
    public int getQuantity() { ... }
    public void setQuantity(int quantity) { ... }

    public int defaultProduct() {
        return 1;
    }

Alternatives

There are, in fact, two other ways to set properties of a newly instantiated object to default values.

The first is to use the created() callback, called by the framework when DomainObjectContainer#newTransientInstance(…) is called. This method is called after any dependencies have been injected into the service.

The second is more straightforward: simply initialize properties in the constructor. However, this cannot use any injected services as they will not have been initialized.

2.1.6. `disable…()`

The disable…() supporting method is called for properties, collections and actions. It allows the modification of the property/collection to be vetoed (ie made read-only) and to prevent the invocation of the action ("grey it out").

Directly mutable collections are not currently supported by the Wicket viewer; they are always implicitly disabled.

Typically modification/invocation is vetoed based on the state of the domain object being interacted with, though it could be any reason at all (eg the current date/time of the interaction, or the state of some other related data such as stock levels, or the identity of the calling user).

The reason for vetoing a modification/invocation is normally returned as a string. However, Apache Isis' i18n support extends this so that reasons can be internationalized.

The signature of the supporting method is simply:

public String disableXxx() { ... }

where the returned string is the reason the property cannot be edited, or the action invoked.

For i18n, the supporting method returns a TranslatableString:

public TranslatableString disableXxx() { ... }

The returned string is then automatically translated to the locale of the current user.

For example, to disable an action:

public class Customer {
    public boolean isBlacklisted() { ... }

    public Order placeOrder(
            final Product product,
            @ParameterLayout(named="Quantity")
            final int quantity) {
        ...
    }
    public String disablePlaceOrder() {
        return isBlacklisted()
                    ? "Blacklisted customers cannot place orders"
                    : null;
    }
    ...
}

Or, to disable a property:

public class Customer {
    public boolean isBlacklisted() { ... }

    public BigDecimal getCreditLimit() { ... }
    public void setCreditLimit(BigDecimal creditLimit) { ... }
    public String disableCreditLimit() {
        return isBlacklisted()
                    ? "Cannot change credit limit for blacklisted customers"
                    : null;
    }
    ...
}

In the case of actions, the framework will also search for supporting method that has the exact same parameter types as the action itself. Enabling isis.reflector.validator.noParamsOnly configuration property switches this off, so that the framework will only search for supporting method with no parameters.

Note that enabling this configuration property in effect means that mixins must be used instead of contributed services (because contributed actions are the one case where the value of a parameter to a supporting method may be non-null).

2.1.7. `get…()`

The get…() prefix is simply the normal JavaBean getter prefix that denotes properties or collections.

When Apache Isis builds its metamodel, it first searches for the getter methods, characterizing them as either properties or collections based on the return type. It then refines the metamodel based on the presence of annotations and supporting methods.

All remaining public methods (that do not use one of the Apache Isis prefixes) are interpreted as actions.

Any methods "left over" that do use one of the Apache Isis prefixes, are interpreted to be orphaned. Apache Isis "fails-fast" and will not boot, instead printing an error message to the log so that the issue can be easily diagnosed.

2.1.8. `hide…()`

The hide…() supporting method is called for properties, collections and actions. It allows the property/collection to be completely hidden from view.

It’s comparatively rare for properties or collections to be imperatively hidden from view, but actions are sometimes hidden or shown visible (as opposed to being just disabled, ie greyed out).

The signature of the supporting method is simply:

public boolean hideXxx() { ... }

Returning true will hide the property, collection or action, returning false leaves it visible.

For example, to hide an action:

public class Customer {
    public boolean isBlacklisted() { ... }

    public Order placeOrder(
            final Product product,
            @ParameterLayout(named="Quantity")
            final int quantity) {
        ...
    }
    public boolean hidePlaceOrder() {
        return isBlacklisted();
    }
    ...
}

Or, to hide a property:

public class Customer {
    public boolean isBlacklisted() { ... }

    public BigDecimal getCreditLimit() { ... }
    public void setCreditLimit(BigDecimal creditLimit) { ... }
    public boolean hideCreditLimit() {
        return isBlacklisted();
    }
    ...
}

In the case of actions, the framework will also search for supporting method that has the exact same parameter types as the action itself. Enabling isis.reflector.validator.noParamsOnly configuration property switches this off, so that the framework will only search for supporting method with no parameters.

Note that enabling this configuration property in effect means that mixins must be used instead of contributed services (because contributed actions are the one case where the value of a parameter to a supporting method may be non-null).

2.1.9. `modify…()` (deprecated)

The modify…() supporting method is called — instead of the setter — whenever a property has been set to be set to a new value. Its purpose is to allow additional business logic to be performed.

DataNucleus' smart handling of setters means that this supporting methods are in essence redundant, and so should be considered deprecated.

For example:

public class LibraryMember {
    public Title getFavoriteTitle() { ... }
    public void setFavoriteTitle(Title title) { ... }
    public void modifyFavoriteTitle(Title title) {
        if(getTitle() != null) {
            titleFavoritesService.decrement(getTitle());    (1)
        }
        setFavoriteTitle(title);                            (2)
        titleFavoritesService.decrement(title);             (3)
    }
    public void clearFavoriteTitle() { ... }
    ...
}

1	perform some additional business logic
2	update the property
3	perform some additional business logic

2.1.10. `removeFrom…()` (deprecated)

The removeFrom…() supporting method is called whenever an object is removed from a collection. Its purpose is to allow additional business logic to be performed.

Directly mutable collections are not currently supported by the Wicket viewer. The suggested workaround is to simply define an action.

For example:

public class LibraryMember {
    public SortedSet<Book> getBorrowed() { ... }
    public void setBorrowed(SortedSet<Book> borrowed) { ... }
    public void addToBorrowed(Book book) { ... }
    public void removeFromBorrowed(Book book) {
        getBorrowed().remove(book);                         (1)
        reminderService.removeReminder(this, book);         (2)
    }
    ...
}

1	update the collection
2	perform some additional business logic

2.1.11. `set…()`

The set…() prefix is simply the normal JavaBean setter prefix that denotes writeable properties or collections.

2.1.12. `validate…()`

The validate…() supporting method is called for properties, actions and action parameters. It allows the proposed new value for a property to be rejected, or the proposed argument of an action parameter to be rejected, or to reject a whole set of action arguments for an actio invocation.

The reason for vetoing a modification/invocation is normally returned as a string. However, Apache Isis' i18n support extends this so that reasons can be internationalized if required.

Action Parameter

For an action parameter in (0-based) position N, and of type T, the signature is:

public String validateNXxx(T proposed) { ... }

where the returned string is the reason why the argument is rejected (or null if not vetoed).

For i18n, the supporting method returns a TranslatableString:

public TranslatableString validateNXxx(T proposed) { ... }

The returned string is then automatically translated to the locale of the current user.

For example:

public class Customer {
    public Order placeOrder(
            final Product product,
            @ParameterLayout(named="Quantity")
            final int quantity) {
        ...
    }
    public String validate0PlaceOrder(
            final Product product) {
        return product.isDiscontinued()
                    ? "Product has been discontinued"
                    : null;
    }
    ...
}

Action Parameter Set

In addition to validating a single single action argument, it is also possible to validate a complete set of action arguments. The signature is:

public String validateXxx(...) { ... }

where the returned string is the reason why the argument is rejected (or null if not vetoed), and the supporting method takes the same parameter types as the action itself.

For i18n, the supporting method returns a TranslatableString:

public TranslatableString validateXxx(...) { ... }

For example:

public class Customer {
    public Order placeOrder(
            final Product product,
            @ParameterLayout(named="Quantity")
            final int quantity) {
        ...
    }
    public String validatePlaceOrder(
            final Product product,
            final int quantity) {
        return quantity > product.getOrderLimit()
                    ? "May not order more than " + product.getOrderLimit() + " items for this product"
                    : null;
    }
    ...
}

Properties

For properties of type T the signature of the supporting method is:

public String validateXxx(T proposed) { ... }

where the returned string is the reason the modification is vetoed (or null if not vetoed).

For i18n, the supporting method returns a TranslatableString:

public TranslatableString validateXxx(T proposed) { ... }

For example:

public class Customer {
    public BigDecimal getCreditLimit() { ... }
    public void setCreditLimit(BigDecimal creditLimit) { ... }
    public validateCreditLimit(BigDecimal creditLimit) {
        return creditLimit.compareTo(BigDecimal.ZERO) < 0
                    ? "Credit limit cannot be negative"
                    : null;
    }
    ...
}

2.1.13. `validateAddTo…()` (deprecated)

The validateAddTo…() supporting method is called whenever an object is to be added to a collection. Its purpose is to validate the proposed object and possibly veto the change.

Directly mutable collections are not currently supported by the Wicket viewer. The suggested workaround is to simply define an action.

The signature of the supporting method for a collection with element type E is:

public String validateAddToXxx(E element) { ... }

where the returned string is the reason the collection modification invocation is vetoed (or null if not vetoed). Apache Isis' i18n support extends this so that reasons can be internationalized if required.

For example:

public class LibraryMember {
    public SortedSet<Book> getBorrowed() { ... }
    public void setBorrowed(SortedSet<Book> borrowed) { ... }
    public String validateAddToBorrowed(Book book) {
        return book.isReference()? "Reference books cannot be borrowed": null;
    }
    public void validateRemoveFromBorrowed(Book book) { ... }
    ...
}

2.1.14. `validateRemoveFrom…()` (deprecated)

The validateRemoveFrom…() supporting method is called whenever an object is to be removed from a collection. Its purpose is to validate the proposed object removal and possibly veto the change.

Directly mutable collections are not currently supported by the Wicket viewer. The suggested workaround is to simply define an action.

The signature of the supporting method for a collection with element type E is:

public String validateRemoveFromXxx(E element) { ... }

where the returned string is the reason the collection modification invocation is vetoed (or null if not vetoed). Apache Isis' i18n support extends this so that reasons can be internationalized if required.

For example:

public class LibraryMember {
    public SortedSet<Book> getBorrowed() { ... }
    public void setBorrowed(SortedSet<Book> borrowed) { ... }
    public String validateAddToBorrowed(Book book) { ... }
    public void validateRemoveFromBorrowed(Book book) {
        return !book.hasBeenReadBy(this)? "You didn't read this book yet": null;
    }
    ...
}

2.2. Reserved Methods

The table below lists the reserved methods that are recognized as part of Apache Isis' default programming model.

Table 2. Reserved Methods
Method	Description
`cssClass()`	Provides a CSS class for this object instance. In conjunction with `application.css`, can therefore provide custom styling of an object instance wherever it is rendered. See also `title()` and `iconName()`.
`disable(…)`	Disable all or some of an object’s properties
`getId()`	Provides an optional unique identifier of a service. If not provided, the service’s fully-qualified class name is used.
`hide(…)`	Hide all or some of an object’s properties
`iconName()`	Provides the name of the image to render, usually alongside the title, to represent the object. If not provided, then the class name is used to locate an image. See also `title()` and `cssClass()`
`title()`	Provides a title for the object. See also `iconName()` and `cssClass()`
`validate()`	Validate the object’s state prior to persisting.

2.2.1. `cssClass()`

The cssClass() returns a CSS class for a particular object instance.

The Wicket viewer wraps the object’s representation in a containing <div> with the class added. This is done both for rendering the object either in a table or when rendering the object on its own page.

In conjunction with application.css, can therefore provide custom styling of an object instance wherever it is rendered.

For example, the (non-ASF) Isis addons' todoapp uses this technique to add a strikethrough for completed todo items. This is shown on the home page:

The code to accomplish this is straightforward:

public class ToDoItem ... {
    public String cssClass() {
        return !isComplete() ? "todo" : "done";
    }
    ...
}

In the application.css, the following styles were then added:

tr.todo {
}
tr.done {
    text-decoration: line-through;
    color: #d3d3d3;
}

2.2.2. `disabled()`

One use case that Apache Isis supports is that of a domain object with a lifecycle whereby at some stage it should become immutable: all its properties/collections should be disabled, and/or its actions become not invokable.

It would be painful to have to write a separate disable…() method for each and every member, so instead Isis allows a single disable…(…) method to be implemented that is applied to all members.

The signature of the method is:

public String disabled(Identifier.Type identifierType) { ... }

where Identifier.Type is part of the Isis applib (nested static class of o.a.i.applib.Identifier) to distinguish between an interaction with an action, a property or an action.

Note that Apache Isis' i18n support extends this so that the returned reason can also be internationalized.

For example:

public String disabled(Identifier.Type identifierType) {
    return !calendarService.isOfficeHours(clock.today()
            ? "Cannot modify objects outside of office hours"
            : null;
}

See also the similar methods to hide() object members en-masse.

Alternatives

An alternative design — and one that could be easily argued is actually more flexible — is to leverage domain events with vetoing subscribers.

With this approach we define, for a given domain class, a base PropertyDomainEvent, CollectionDomainEvent and ActionDomainEvent. A good pattern is to make these nested static classes. For example:

public class ToDoItem ... {
    public static abstract class PropertyDomainEvent<T>
            extends ToDoAppDomainModule.PropertyDomainEvent<ToDoItem, T> {
        ...
    }
    ...
}

where in turn:

public final class ToDoAppDomainModule {
    private ToDoAppDomainModule(){}
    public abstract static class PropertyDomainEvent<S,T>
            extends org.apache.isis.applib.services.eventbus.PropertyDomainEvent<S,T> {
        ...
    }
    ...
}

Then, each property/collection/action emits either these base domain events or their own subclass:

public class ToDoItem ... {
    public static class DescriptionDomainEvent
            extends PropertyDomainEvent<String> {
        ...
    }
    @Property(
        domainEvent = DescriptionDomainEvent.class
    )
    public String getDescription() { ... }
    ...
}

A vetoing subscriber can then subscribe to the domain events and veto access, eg:

@DomainObject
public class VetoOutOfOfficeHours {
    @Subscribe
    public void on(ToDoItem.PropertyDomainEvent ev) {
        if(!calendarService.isOfficeHours(clock.today()) {
            ev.veto("Cannot modify objects outside of office hours");
        }
    }
    ...
}

Obviously there’s an awful lot more boilerplate here, but there’s also a lot more flexibility.

2.2.3. `getId()`

The getId() method applies only to domain services, and is used to provide a unique alias for the domain service’s class name.

This value is used internally to generate a string representation of an service identity (the Oid). This can appear in several contexts, including:

as the value of Bookmark#getObjectType() and in the toString() value of Bookmark (see BookmarkService)
in the serialization of OidDto in the command and interaction schemas
in the URLs of the RestfulObjects viewer
in the URLs of the Wicket viewer (specifically, for bookmarked actions)

Example

For example:

@DomainService
public class OrderMenu {
    ...
    public String getId() { return "orders.OrderMenu"; }
}

Precedence

The rules of precedence are:

@DomainService#objectType()
getId()
The fully qualified class name.

This might be obvious, but to make explicit: we recommend that you always specify an object type for your domain services.

Otherwise, if you refactor your code (change class name or move package), then any externally held references to the OID of the service will break. At best this will require a data migration in the database; at worst it could cause external clients accessing data through the Restful Objects viewer to break.

If the object type is not unique across all domain classes then the framework will fail-fast and fail to boot. An error message will be printed in the log to help you determine which classes have duplicate object tyoes.

2.2.4. `hide()`

One use case that Apache Isis supports is that of a domain object with a lifecycle whereby at some stage some number of the object’s members should be hidden. For example, for an object that at some stage is logically immutable, we might want to make all its properties/collections unmodifiable and hide all its actions.

While we could write a separate hide…() method for each and every action, this could become painful. So instead Isis allows a single hide…(…) method to be implemented that is applied to all members.

The signature of the method is:

public boolean hide(Identifier.Type identifierType) { ... }

where Identifier.Type is part of the Isis applib (nested static class of o.a.i.applib.Identifier) to distinguish between an interaction with an action, a property or an action.

For example:

public boolean hide(Identifier.Type identifierType) {
    return identifierType == Identifier.Type.ACTION && isFrozen();
}

See also the similar method to disable() object members en-masse.

Alternatives

An alternative design — and one that could be easily argued is actually more flexible — is to leverage domain events with vetoing subscribers.

There is further discussion on this approach in here.

2.2.5. `iconName()`

Every object is represented by an icon; this is based on the domain object’s simple name. The Wicket viewer searches for the image in the same package as the .class file for the domain object or in the images package. It will find any matching name and one of the followign suffexes png, gif, jpeg, jpg, svg. If none is found, then Default.png will be used as fallback.

The iconName() allows the icon that to be used to change for individual object instances. These are usually quite subtle, for example to reflect the particular status of an object. The value returned by the iconName() method is added as a suffix to the base icon name.

For example, the (non-ASF) Isis addons' todoapp uses this technique to add an overlay for todo items that have been completed:

The screenshot below shows the location of these png icon files:

The code to accomplish this is straightforward:

public class ToDoItem ... {
    public String iconName() {
        return !isComplete() ? "todo" : "done";
    }
    ...
}

2.2.6. `title()`

Every object is represented by a title. This appears both as a main header for the object when viewed as well as being used as a hyperlink within properties and collections. It therefore must contain enough information for the end-user to distinguish the object from any others.

This is most commonly done by including some unique key within the title, for example a customer’s SSN, or an order number, and so forth. However note that Apache Isis itself does not require the title to be unique; it is merely recommended in most cases.

An object’s title can be constructed in various ways, but the most flexible is to use the title() method. The signature of this method is usually:

public String title() { ... }

Note that Apache Isis' i18n support extends this so that titles can also be internationalized.

For example, the (non-ASF) Isis addons' todoapp uses this technique to add an overlay for todo items that have been completed:

public String title() {
    final TitleBuffer buf = new TitleBuffer();                              (1)
    buf.append(getDescription());
    if (isComplete()) {                                                     (2)
        buf.append("- Completed!");
    } else {
        try {
            final LocalDate dueBy = wrapperFactory.wrap(this).getDueBy();   (3)
            if (dueBy != null) {
                buf.append(" due by", dueBy);
            }
        } catch(final HiddenException ignored) {                            (4)
        }
    }
    return buf.toString();
}

1	simple tility class to help construct the title string
2	imperative conditional logic
3	using the `WrapperFactory` to determine if the `dueBy` field is visible for this user …
4	… but ignore if not

As the example above shows, the implementation can be as complex as you like.

In many cases, though, you may be able to use the @Title annotation.

2.2.7. `validate()`

The validate() method is used to specify that invariants pertaining to an object’s state are enforced.

(As of 1.8.0) there are known limitations with this functionality. Invariants are enforced when an object is initially created and when it is edited, however invariants are currently not enforced if an action is invoked.

The signature of the method is:

public String validate() { ... }

where the returned string is the reason that the invocation is vetoed.

Note that Apache Isis' i18n support extends this so that the returned reason can also be internationalized.

2.3. Lifecycle Methods

The lifecycle callback methods notify a domain entity about its interaction within the persistence lifecycle. For example, the entity is notified immediately prior to being persisted, or when it is about to be updated.

Note that these callbacks are fired by Apache Isis rather than JDO. In the future we may deprecate them because there are better mechanisms available using listeners/subscribers:

in Isis 1.9.0 and earlier, you may therefore want to consider using the JDO API directly to set up a lifecycle listener; see here for further discussion.
alternatively, you can use a subscriber for the lifecycle events fired in Isis.

The lifecycle callback methods supported by Isis are:

Table 3. Lifecycle methods (partial support)
Method	Description
`created()`	called when an object has just been created using `newTransientInstance()`
`loaded()`	called when a (persistent) object has just been loaded from the object store.
`persisted()`	called when object has just been persisted from the object store.
`persisting()`	called when a (not-yet-persistent) object is just about to be persisted from the object store
`removed()`	called when a (persistent) object has just been deleted from the object store
`removing()`	called when a (persistent) object is just about to be deleted from the object store
`updated()`	called when a (persistent) object has just been updated in the object store
`updating()`	called when a (persistent) object is just about to be updated in the object store

Some lifecycle methods have been deprecated:

Method Notes

deleted()

Replaced by removed()

deleting()

Replaced by removing()

loading()

callback for when the (persistent) object is just about to be loaded from the object store.

This method is never called.

saved()

Replaced by persisted()

saving()

Replaced by persisting()

2.3.1. `created()`

The created() lifecycle callback method is called when an object has just been created using newTransientInstance()

Alternatively, consider using a event bus subscriber on the ObjectCreatedEvent.

2.3.2. `loaded()`

The loaded() lifecycle callback method is called when a (persistent) object has just been loaded from the object store.

Alternatively, consider using a event bus subscriber on the ObjectLoadedEvent.

2.3.3. `persisted()`

The persisted() lifecycle callback method is called when object has just been persisted from the object store.

2.3.4. `persisting()`

The persisting() lifecycle callback method is called when a (not-yet-persistent) object is just about to be persisted from the object store

2.3.5. `removed()`

The removed() lifecycle callback method is called when a (persistent) object has just been deleted from the object store

2.3.6. `removing()`

The removing() lifecycle callback method is called when a (persistent) object is just about to be deleted from the object store

2.3.7. `updated()`

The updated() lifecycle callback method is called when a (persistent) object has just been updated in the object store

2.3.8. `updating()`

The updating() lifecycle callback method is called when a (persistent) object is just about to be updated in the object store

2.3.9. Using the JDO API

As an alternative to relying on Apache Isis to call lifecycle callback methods, you could instead use the JDO lifecycle listener API directly.

We may decide to deprecate the Apache Isis callbacks in the future because they merely duplicate this functionality already available in JDO.

You can gain access to the relevant JDO API using the IsisJdoSupport domain service.

For example:

@RequestScoped                                                   (1)
@DomainService(nature=NatureOfService.DOMAIN)
public class ObjectChangedListenerService
        implements javax.jdo.listener.StoreLifecycleListener {   (2)
    @Programmatic
    @PostConstruct
    public void init() {
        getPmFactory().addInstanceLifecycleListener(this);
    }
    @Programmatic
    @PreDestroy
    public void tidyUp() {
        getPmFactory().removeInstanceLifecycleListener(this);
    }
    private PersistenceManager getPersistenceManager() {
        return jdoSupport.getPersistenceManager();               (3)
    }
    @Programmatic
    public void preStore (InstanceLifecycleEvent event) { ... }
    @Programmatic
    public void postStore (InstanceLifecycleEvent event) { ... }
    @Inject
    IsisJdoSupport jdoSupport;
}

1	must be `@RequestScoped` because we register on the `PersistenceManager`, which is different for each request.
2	implement whichever callback lifecycle listeners are of interest
3	use the injected `IsisJdoSupport` service to obtain the `PersistenceManager`.

Note that it isn’t possible to register on the PersistenceManagerFactory because listeners cannot be attached once a persistence session has been created (which it will have been when the service’s @PostConstruct method is called).

3. Classes and Interfaces

This chapter describes the usage of various classes and interfaces that are not otherwise associated with domain services, object layout or configuration.

3.1. `AppManifest` (bootstrapping)

This section describes how to implement the AppManifest interface to bootstrap both an Apache Isis web application, and also its integration tests.

(As of 1.15.0), the framework-provided AppManifestAbstract and AppManifestAbstract.Builder make it easy to write AppManifest that can be used both to bootstrap the application "proper", and to be tweaked for use within integration tests.

3.1.1. API

The AppManifest interface allows the constituent parts of an application to be defined programmatically, most specifically the packages that contain domain services and/or persistent entities. Its API is defined as:

public interface AppManifest {
    public List<Class<?>> getModules();                         (1)
    public List<Class<?>> getAdditionalServices();              (2)
    public String getAuthenticationMechanism();                 (3)
    public String getAuthorizationMechanism();                  (4)
    public List<Class<? extends FixtureScript>> getFixtures();  (5)
    public Map<String,String> getConfigurationProperties();     (6)
}

1	Must return a non-null list of classes, each of which representing the root of one of the modules containing services and possibly entities, which together makes up the running application.
2	If non-`null`, overrides the value of `isis.services` configuration property to specify a list of additional classes to be instantiated as domain services (over and above the domain services defined via `getModules()` method.
3	If non-`null`, overrides the value of `isis.authentication` configuration property to specify the authentication mechanism.
4	If non-`null`, overrides the value of `isis.authorization` configuration property to specify the authorization mechanism.
5	If non-`null`, overrides the value of `isis.fixtures` configuration property to specify a fixture script to be installed.
6	Overrides for any other configuration properties.

The following sections describe each of these methods in a little more detail.

`getModules()`

The most significant method (the only one which must return a non-null value) is the getModules() method. Each module is identified by a class; the framework simply uses that class' package as the root to search for domain services (annotated with @DomainService) and entities (annotated with @PersistenceCapable). Generally there is one such module class per Maven module.

A module class for a domain module might for example be defined as:

package com.mycompany.myapp.dom;
public final class MyAppDomainModule {
    private MyAppDomainModule() {}
}

This tells the framework that the package and subpackages under com.mycompany.myapp.dom should be searched for domain services (annotated with @DomainService), mixins (@Mixin) and entities (@PersistenceCapabable).

As is perhaps apparent, the getModules() method replaces and overrides both the isis.services.ServicesInstallerFromAnnotation.packagePrefix key (usually found in the isis.properties file) and also the`isis.persistor.datanucleus.RegisterEntities.packagePrefix` key (usually found in the persistor_datanucleus.properties file). The value of the isis.services-installer configuration property is also ignored.

For example, the (non-ASF) Isis addons' todoapp defines the following:

@Override
public List<Class<?>> getModules() {
    return Arrays.asList(
            ToDoAppDomainModule.class,
            ToDoAppFixtureModule.class,
            ToDoAppAppModule.class,
            org.isisaddons.module.audit.AuditModule.class,
            org.isisaddons.module.command.CommandModule.class,
            org.isisaddons.module.devutils.DevUtilsModule.class,
            org.isisaddons.module.docx.DocxModule.class,
            org.isisaddons.module.publishing.PublishingModule.class,
            org.isisaddons.module.sessionlogger.SessionLoggerModule.class,
            org.isisaddons.module.settings.SettingsModule.class,
            org.isisaddons.wicket.gmap3.cpt.service.Gmap3ServiceModule.class
    );
}

As can be seen, the various (non-ASF) Incode Platform modules also each provide a module class that can be easily referenced.

`getAdditionalServices()`

We normally we recommend that services are defined exclusively through getModules(), and that this method should therefore return an empty list. However, there are certain use cases where the a service must be explicitly specified either because the service required does not (for whatever reason) have a @DomainService annotation.

For example, the (non-ASF) Incode Platform's security module allows the policy to evaluate conflicting permissions to be specified by explicitly registering either the PermissionsEvaluationServiceAllowBeatsVeto domain service or the PermissionsEvaluationServiceVetoBeatsAllow domain service:

@Override
public List<Class<?>> getAdditionalServices() {
    return Arrays.asList(
            org.isisaddons.module.security.dom.permission.PermissionsEvaluationServiceVetoBeatsAllow.class
    );
}

If this method returns a non-null value, then it overrides the value of isis.services configuration property.

`getAuthenticationMechanism()`

If non-null, this method specifies the authentication mechanism to use. The valid values are currently "shiro" or "bypass". If null is returned then the value of the isis.authentication configuration property (in isis.properties file) is used instead.

See the security guide for further details on configuring shiro or bypass security.

This property is ignored for integration tests (which always uses the "bypass" mechanism).

`getAuthorizationMechanism()`

If non-null, this method specifies the authorization mechanism to use. The valid values are currently "shiro" or "bypass". If null is returned then the value of the isis.authorization configuration property (in isis.properties file) is used instead.

See the security guide for further details on configuring shiro or bypass security.

This property is ignored for integration tests (which always uses the "bypass" mechanism).

`getFixtures()`

If non-null, this method specifies the fixture script(s) to be run on startup. This is particularly useful when developing or demoing while using an in-memory database.

For example:

@Override
public List<Class<? extends FixtureScript>> getFixtures() {
    return Lists.newArrayList(todoapp.fixture.demo.DemoFixture.class);
}

Note that in order for fixtures to be installed it is also necessary to set the isis.persistor.datanucleus.install-fixtures key to true. This can most easily be done using the getConfigurationProperties() method, discussed below.

`getConfigurationProperties()`

This method allow arbitrary other configuration properties to be overridden. One common use case is in conjunction with the getFixtures() method, discussed above:

@Override
public Map<String, String> getConfigurationProperties() {
    Map<String, String> props = Maps.newHashMap();
    props.put("isis.persistor.datanucleus.install-fixtures", "true");
    return props;
}

3.1.2. Bootstrapping

One of the primary goals of the AppManifest is to unify the bootstrapping of both integration tests and the webapp. This requires that the integration tests and webapp can both reference the implementation.

We strongly recommend using a myapp-app Maven module to hold the implementation of the AppManifest. This Maven module can then also hold dependencies which are common to both integration tests and the webapp, specifically the org.apache.isis.core:isis-core-runtime and the org.apache.isis.core:isis-core-wrapper modules.

We also strongly recommend that any application-layer domain services and view models (code that references persistent domain entities but that is not referenced back) is moved to this myapp-app module. This will allow the architectural layering of the overall application to be enforced by Maven.

What then remains is to update the bootstrapping code itself.

There are several different contexts in which the framework needs to be bootstrapped:

the first is as a "regular" webapp (using the Wicket viewer). Here the AppManifest just needs to be specified as a configuration property, usually done using the WEB-INF/isis.properties configuration file:
```
isis.appManifest=domainapp.app.MyAppAppManifest
```
the second is also as a webapp, but from within the context of the IDE.

Here, it’s common to use the org.apache.isis.WebServer class to launch your application from the command line. This allows the AppManifest to be specified using the -m (or --manifest) flag:
```
java org.apache.isis.WebServer -m com.mycompany.myapp.MyAppAppManifestWithFixtures
```
the third case is within an integration test.

The code to boostrap an integration test is shown in the testing guide, but once again an AppManifest is required.

In some cases an integration test uses the exact same AppManifest as the regular webapp. Sometimes though it is necessary to "tweak" the AppManifest:

it might use additional services, such as services to mock out external dependencies, or to provide fake data
it might override certain configuration properties, eg to run against an in-memory HSQLDB database.

The next section describes some helper classes that the framework provides to help achieve this.

AppManifestAbstract

(As of 1.15.0), the AppManifestAbstract and its associated builder (AppManifestAbstract.Builder) make it easy to bootstrap the application both as a webapp and also as an integration test.

Rather than implement AppManifest interface directly, instead your application subclasses from AppManifestAbstract. This takes an instance of a AppManifestAbstract.Builder in its constructor; the builder is what allows for variation between environments.

Moreover, these classes recognise that configuration properties fall into two broad classes:

those that are fixed and do not change between environments.

In other words these describe how the application chooses to configure the framework itself, eg global disable of editing of properties, or enabling of auditing.
those that change between environments.

The classic example here is the JDBC URL.

For example, the SimpleApp archetype's AppManifest is defined as:

public class DomainAppAppManifest extends AppManifestAbstract {

    public static final Builder BUILDER = Builder.forModules(
                    SimpleModuleDomSubmodule.class,                         (1)
                    DomainAppApplicationModuleFixtureSubmodule.class,
                    DomainAppApplicationModuleServicesSubmodule.class
            )
            .withConfigurationPropertiesFile(DomainAppAppManifest.class,    (2)
                    "isis.properties",
                    "authentication_shiro.properties",
                    "persistor_datanucleus.properties",
                    "viewer_restfulobjects.properties",
                    "viewer_wicket.properties"
            ).withAuthMechanism("shiro");                                   (3)

    public DomainAppAppManifest() {
        super(BUILDER);                                                     (4)
    }
}

1	the modules that make up the application; corresponds to `AppManifest#getModules()`
2	the (non-changing with environment) set of configuration properties, loaded relative to the manifest itself; corresponds to `AppManifest#getConfigurationProperties()`
3	override of components; correponds to both `AppManifest#getAuthenticationMechanism()` and `AppManifest#getAuthorizationMechanism()`
4	Pass the builder up to the superclass.

If the integration tests requires no tweaking, then the AppManifest can be used directly, for example:

public abstract class DomainAppIntegTestAbstract extends IntegrationTestAbstract2 {
    @BeforeClass
    public static void initSystem() {
        bootstrapUsing(new DomainAppAppManifest());
    }
}

On the other hand, if tweaking is required then exposing the builder as a public static field makes this easy to do:

public abstract class DomainAppIntegTestAbstract extends IntegrationTestAbstract2 {
    @BeforeClass
    public static void initSystem() {
        bootstrapUsing(DomainAppAppManifest.BUILDER
                            .withAdditionalModules(...)
                            .withAdditionalServices(...)
                            .withConfigurationPropertiesFile("...")
                            .withConfigurationProperty("...","...")
                            .build()
        );
    }
}

3.1.3. Subsidiary Goals

There are a number of subsidiary goals of the AppManifest class (though not all of these are fully implemented):

Allow different integration tests to run with different manifests.
- Normally the running application is shared (on a thread-local) between integration tests. What the framework could perhaps do is to be intelligent enough to keep track of the manifest in use for each integration test and tear down the shared state if the "next" test uses a different manifest
Provide a programmatic way to contribute elements of web.xml.
Provide a programmatic way to configure Shiro security.
Anticipate the module changes forthcoming in Java 9.
- Eventually we see that the AppManifest class acting as an "aggregator", with the list of modules will become Java 9 modules each advertising the types that they export.
- It might even be possible for AppManifests to be switched on and off dynamically (eg if Java9 is compatible with OSGi, being one of the design goals).

3.2. Superclasses

This section catalogues the various convenience (non event) superclasses defined by Apache Isis. These are listed in the table below.

Table 5. Convenience Superclasses
API	Maven Module Impl’n (g: a:)	Implementation	Notes
`o.a.i.applib.` `AbstractContainedObject`	`o.a.i.core` `isis-core-applib`	(abstract class)
`o.a.i.applib.` `AbstractDomainObject`	`o.a.i.core` `isis-core-applib`	(abstract class)
`o.a.i.applib.` `AbstractFactoryAndRepository`	`o.a.i.core` `isis-core-applib`	(abstract class)
`o.a.i.applib.` `AbstractService`	`o.a.i.core` `isis-core-applib`	(abstract class)
`o.a.i.applib.` `AbstractSubscriber`	`o.a.i.core` `isis-core-applib`	(abstract class)
`o.a.i.applib.` `AbstractViewModel`	`o.a.i.core` `isis-core-applib`	(abstract class)
`o.a.i.applib.` `fixturescript` `FixtureScript`	`o.a.i.core` `isis-core-applib`	(abstract class)
`o.a.i.applib.` `fixturescripts` `FixtureScripts`	`o.a.i.core` `isis-core-applib`	(abstract class). `FixtureScriptsDefault` is a default implementation that is used when the alternative `FixtureScriptsSpecificationProvider` is provided (and no other implementation of `FixtureScripts` was found).	depends on: `ClassDiscoveryService`

3.2.1. `AbstractContainedObject`

This class is a convenience superclass for domain objects and services, providing general purpose methods for interacting with the framework. These include:

allMatches(Query) - search for all objects matching the specified Query.

+ Note that this, and other similar methods (eg firstMatch(…), uniqueMatch(…)) will automatically flush the current transaction.
newTransientInstance(Class) - to create a new instance of an object, with any services injected into it
persistIfNotAlready(Object) - to persist an object

In fact, the object is queued up to be persisted, and is only actually persisted either when the transaction commits, or when the transaction is flushed (typically when a query is performed).
warnUser(String) - generate a warning to the user
getContainer() - which returns the DomainObjectContainer

Each of these methods simply delegates to an equivalent method in DomainObjectContainer.

In practice we find that there’s little to gain from subclassing; it’s easier/less obscure to simply inject DomainObjectContainer into a simple pojo class.

3.2.2. `AbstractDomainObject`

This class extends AbstractContainedObject, adding in convenience methods for managing the persistence lifecycle of the object instance.

Each of these methods, eg isPersistent(…), delegates to an equivalent method in DomainObjectContainer.

3.2.3. `AbstractFactoryAndRepository`

This class extends AbstractContainedObject. Its intent was to be a convenience subclass for services acting as either a repository or a factory, however note that all of the methods that it defines are now deprecated.

Instead, indicate that a service is repository using the @DomainService#repositoryFor() attribute.

3.2.4. `AbstractService`

This class extends AbstractContainedObject, adding in an implementation of getId() based upon the classes name.

In practice there is little to gain from subclassing; simply inject DomainObjectContainer for broadly equivalent functionality.

3.2.5. `AbstractSubscriber`

This is a convenience superclass for creating subscriber domain services on the EventBusService. It uses @PostConstruct and @PreDestroy callbacks to automatically register/unregister itself with the EventBusService.

It’s important that subscribers register before any domain services that might emit events on the EventBusService. For example, the (non-ASF) Incode Platform security module provides a domain service that automatically seeds certain domain entities; these will generate lifecycle events and so any subscribers must be registered before such seed services. The easiest way to do this is to use the @DomainServiceLayout#menuOrder() attribute.

As a convenience, the AbstractSubscriber specifies this attribute.

3.2.6. `AbstractViewModel`

This class extends AbstractContainedObject, also implementing the ViewModel interface. In and of itself it provides no new behaviour.

As an alternative, consider simply annotating the view model class with {@link org.apache.isis.applib.annotation.ViewModel}.

3.2.7. `FixtureScript`

The FixtureScript class is an abstract class defining an API to set up data within the object store, either for integration tests or while demoing/prototyping.

The primary method that subclasses must implement is:

protected abstract void execute(final ExecutionContext executionContext);

In this method the fixture script can in theory do anything, but in practice it is recommended that it uses injected domain services to set up data. The provided ExecutionContext is used to invoke child fixture scripts, and alsocan be used to store references to any created objects (so that the calling test can access these objects/so that they are rendered in the view model).

See the see the user guide’s testing chapter for further discussion on the use of fixture scripts, in particular fixture scripts' API and usage.

3.2.8. `FixtureScripts`

This abstract class is intended to allow a domain service that can execute FixtureScripts to be easily written.

However, it has now been deprecated; instead we recommend that the FixtureScriptsSpecificationProvider service is implemented instead. The framework will then automatically use FixtureScriptsDefault as a fallback implementation of this class.

See the see the user guide’s testing chapter for further discussion on the use of fixture scripts, in particular fixture scripts' API and usage.

3.3. Domain Event Classes

This section catalogues the various domain event classes defined by Apache Isis.

These events are broadcast on the EventBusService. The domain events are broadcast as a result of being specified in the @Action#domainEvent(), @Property#domainEvent() or @Collection#domainEvent() attributes.

They are listed in the table below.

Table 6. Domain Event Classes
API	Maven Module Impl’n (g: a:)	Implementation	Notes
`o.a.i.applib.` `AbstractDomainEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class)	Superclass of the other domain events, listed below in this table.
`o.a.i.applib.` `ActionDomainEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `ActionDomainEvent.Default` is the concrete implementation used if no `@Action#domainEvent` attribute is specified	Broadcast whenever there is an interaction (hide/disable/validate/pre-execute/post-execute) with an object’s action.
`o.a.i.applib.` `CollectionDomainEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `CollectionDomainEvent.Default` is the concrete implementation used if no `@Collection#domainEvent` attribute is specified.	Broadcast whenever there is an interaction (hide/disable/validate/access) with an object’s collection.
`o.a.i.applib.` `PropertyDomainEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `PropertyDomainEvent.Default` is the concrete implementation used if no `@Propert#domainEvent` attribute is specified	Broadcast whenever there is an interaction (hide/disable/validate/access) with an object’s property.

3.3.1. `AbstractDomainEvent`

This class is the superclass for all domain events that are raised by the framework when interacting with actions, properties or collections.

Its immediate subclasses are:

The main purpose of the class is to define the protocol by which subscribers can influence an interaction (eg hide a collection, disable a property, validate action arguments). It class also provides a simple mechanism to allow adhoc sharing of user data between different phases.

API

The API of the class is:

public abstract class AbstractDomainEvent<S> extends java.util.EventObject {

    public Phase getEventPhase();                                   (1)
    public S getSource();                                           (2)
    public Identifier getIdentifier();                              (3)

    public void hide();                                             (4)
    public boolean isHidden();                                      (5)

    public void disable(final String reason);                       (6)
    public void disable(final TranslatableString reason);
    public String getDisabledReason();                              (7)
    public TranslatableString getDisabledReasonTranslatable();
    public boolean isDisabled();

    public void invalidate(final String reason);                    (8)
    public void invalidate(final TranslatableString reason);
    public String getInvalidityReason();                            (9)
    public TranslatableString getInvalidityReasonTranslatable();
    public boolean isInvalid();

    public void veto(final String reason, final Object... args);    (10)
    public void veto(final TranslatableString translatableReason);

    public Object get(Object key);                                  (11)
    public void put(Object key, Object value);
}

1	Whether the framework is checking visibility, enablement, validity or actually executing (invoking action, editing property), as per the `Phase` enum (defined below).
2	The domain object raising this event
3	Identifier of the action, property or collection being interacted with.
4	API for subscribers to hide the member
5	Used by the framework to determine if the member should be hidden (not rendered)
6	API for subscribers to disable the member, specifying the reason why (possibly translated)
7	Used by the framework to determine whether the member should be disabled (greyed out) when rendered.
8	API for subscribers to invalidate an interaction, eg invalid arguments to an action
9	Used by the framework to determine whether the interaction is invalid and should be blocked (eg pressing OK shows message)
10	Convenience API for subscribers to veto; will automatically call either `hide()`, `disable(…)` or `invalidate(…)` based on the phase
11	Mechanism to allow subscribers to share arbitrary information between phases. One event instance is used for both the hide and disable phases, and a different event instance is shared between validate/pre-execute/post-execute.

The referenced Phase enum is in turn:

public enum Phase {
    HIDE,
    DISABLE,
    VALIDATE,
    EXECUTING,
    EXECUTED;
    public boolean isValidatingOrLater();    (1)
}

1	The significance being that at this point the proposed values/arguments are known, and so the event can be fully populated.

3.3.2. `ActionDomainEvent`

Subclass of AbstractDomainEvent for actions.

The class has a number of responsibilities (in addition to those it inherits):

capture the target object being interacted with
capture the arguments for each of the action’s parameters
provide selected metadata about the action parameters from the metamodel (names, types)
link back to the CommandContext service’s Command object

The class itself is instantiated automatically by the framework whenever interacting with a rendered object’s action.

API

The API of the class is:

public abstract class ActionDomainEvent<S> extends AbstractDomainEvent<S> {

    public static class Default extends ActionDomainEvent<Object> { ... }   (1)
    public static class Noop extends ActionDomainEvent<Object> { ... }      (2)
    public static class Doop extends ActionDomainEvent<Object> { ... }      (3)

    @Deprecated
    public Command getCommand();                                            (4)

    public SemanticsOf getSemantics();

    public List<String> getParameterNames();
    public List<Class<?>> getParameterTypes();

    public Object getMixedIn();                                             (5)
    public List<Object> getArguments();                                     (6)
    public Object getReturnValue();                                         (7)
}

1	The `Default` nested static class is the default for the `@Action#domainEvent()` annotation attribute. Whether this raises an event or not depends upon the `isis.reflector.facet.actionAnnotation.domainEvent.postForDefault` configuration property.
2	The `Noop` class is provided as a convenience to indicate that an event should not be posted (irrespective of the configuration property setting).
3	Similarly, the `Doop` class is provided as a convenience to indicate that an event should be raised (irrespective of the configuration property setting).
4	Deprecated, use `CommandContext` or (better) `InteractionContext`instead.
5	Populated only for mixins; holds the underlying domain object that the mixin contributes to.
6	The arguments being used to invoke the action; populated during validate phase and subsequent phases.
7	The value returned by the action; populated only in the executed phase.

3.3.3. `CollectionDomainEvent`

Subclass of AbstractDomainEvent for collections.

The class has a couple of responsibilities (in addition to those it inherits):

capture the target object being interacted with
indicate whether the interaction is to add or remove an object from the collection (or simply to indicate that the collection is being accessed/read)
capture the object reference being added or removed

The class itself is instantiated automatically by the framework whenever interacting with a rendered object’s collection.

API

The API of the class is:

public abstract class CollectionDomainEvent<S,T> extends AbstractDomainEvent<S> {

    public static class Default                                 (1)
        extends CollectionDomainEvent<Object, Object> { ... }
    public static class Noop                                    (2)
        extends CollectionDomainEvent<Object, Object> { ... }
    public static class Doop                                    (3)
        extends CollectionDomainEvent<Object, Object> { ... }

    public T getValue();                                        (4)
    public Of getOf();                                          (5)
}

1	The `Default` nested static class is the default for the `@Collection#domainEvent()` annotation attribute. Whether this raises an event or not depends upon the `isis.reflector.facet.collectionAnnotation.domainEvent.postForDefault` configuration property.
2	The `Noop` class is provided as a convenience to indicate that an event should not be posted (irrespective of the configuration property setting).
3	Similarly, the `Doop` class is provided as a convenience to indicate that an event should be raised (irrespective of the configuration property setting).
4	the object being added or removed
5	whether this is to add or to remove

where the Of enum indicates in turn how the collection is being interacted with:

public static enum Of {
    ACCESS,         (1)
    ADD_TO,         (2)
    REMOVE_FROM     (3)
}

1	collection is being rendered; set during for hide and disable phases
2	collection is being added to; set for validate, executing and executed phases
3	or, collection is being removed from; set for validate, executing and executed phases

3.3.4. `PropertyDomainEvent`

Subclass of AbstractDomainEvent for properties.

The class has a couple of responsibilities (in addition to those it inherits):

capture the target object being interacted with
capture the old and new values of the property

The class itself is instantiated automatically by the framework whenever interacting with a rendered object’s property.

API

The API of the class is:

public abstract class PropertyDomainEvent<S,T> extends AbstractDomainEvent<S> {

    public static class Default                                 (1)
        extends PropertyDomainEvent<Object, Object> { ... }
    public static class Noop                                    (2)
        extends PropertyDomainEvent<Object, Object> { ... }
    public static class Doop                                    (3)
        extends PropertyDomainEvent<Object, Object> { ... }

    public T getOldValue();                                     (4)
    public T getNewValue();                                     (5)
}

1	The `Default` nested static class is the default for the `@Property#domainEvent()` annotation attribute. Whether this raises an event or not depends upon the `isis.reflector.facet.propertyAnnotation.domainEvent.postForDefault` configuration property.
2	The `Noop` class is provided as a convenience to indicate that an event should not be posted (irrespective of the configuration property setting).
3	Similarly, the `Doop` class is provided as a convenience to indicate that an event should be raised (irrespective of the configuration property setting).
4	The pre-modification value of the property; populated at validate and subsequent phases.
5	The proposed (post-modification) value of the property; populated at validate and subsequent phases

3.4. UI Event Classes

This section catalogues the various UI event classes defined by Apache Isis.

These events are broadcast on the EventBusService. The domain events are broadcast as a result of being specified in the @DomainObjectLayout#titleUiEvent(), @DomainObjectLayout#iconUiEvent() or @DomainObjectLayout#cssClassUiEvent() attributes.

They are listed in the table below.

Table 7. UI Event Classes
API	Maven Module Impl’n (g: a:)	Implementation	Notes
`o.a.i.applib.` `TitleUiEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `TitleUiEvent.Default` is the concrete implementation used if no `@DomainObjectLayout#titleUiEvent` attribute is specified	Broadcast whenever there is a requirement to obtain a title for a domain object. Note that if the domain object defines its own `title()` supporting method, or has `@Title` annotation(s) on its properties, then these will take precedence.
`o.a.i.applib.` `IconUiEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `IconUiEvent.Default` is the concrete implementation used if no `@DomainObjectLayout#iconUiEvent` attribute is specified	Broadcast whenever there is a requirement to obtain an icon (or rather, the name of an icon) for a domain object. Note that if the domain object defines its own `iconName()` supporting method, or if it has the `@DomainObjectLayout#cssClassFa()` attribute, then these will take precedence.
`o.a.i.applib.` `CssClassUiEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `CssClassUiEvent.Default` is the concrete implementation used if no `@DomainObjectLayout#cssClassUiEvent` attribute is specified	Broadcast whenever there is a requirement to obtain a CSS class hint for a domain object. Note that if the domain object defines its own `cssClass()` supporting method then this will take precedence.

3.4.1. `TitleUiEvent`

This event class represents a request to obtain the title of a domain object. The class has a number of responsibilities:

capture the target object being interacted with
capture the title, if any, as specified to one of the subscribers

The class itself is instantiated automatically by the framework whenever interacting with a rendered object’s action.

If the domain object defines its own title() supporting method, or has @Title annotation(s) on its properties, then these will take precedence.

3.4.2. `IconUiEvent`

This event class represents a request to obtain the icon (or rather, name of icon) of a domain object. The class has a number of responsibilities:

capture the target object being interacted with
capture the icon (name), if any, as specified to one of the subscribers

The class itself is instantiated automatically by the framework whenever interacting with a rendered object’s action.

If the domain object defines its own iconName() supporting method, or if it has the @DomainObjectLayout#cssClassFa() attribute, then these will take precedence.

3.4.3. `CssClassUiEvent`

This event class represents a request to obtain the a CSS class hint of a domain object. The class has a number of responsibilities:

capture the target object being interacted with
capture the CSS class, if any, as specified to one of the subscribers

The class itself is instantiated automatically by the framework whenever interacting with a rendered object’s action.

if the domain object defines its own cssClass() supporting method then this will take precedence.

3.5. Lifecycle Events

This section catalogues the various lifecycle event classes defined by Apache Isis. These events are fired automatically when a domain object is loaded, created, updated and so forth.

The lifecycle event classes are listed in the table below:

Table 8. Lifecycle Event Classes
API	Maven Module Impl’n (g: a:)	Implementation	Notes
`o.a.i.applib.` `AbstractLifecycleEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class)	Superclass of the other lifecycle events, listed below in this table.
`o.a.i.applib.` `ObjectCreatedEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `ObjectCreatedEvent.Default` is the concrete implementation that is used.	Broadcast when an object is first instantiated using the `DomainObjectContainer`'s `#newTransientInstance(…)` method.
`o.a.i.applib.` `ObjectLoadedEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `ObjectLoadedEvent.Default` is the concrete implementation that is used.	Broadcast when an object is retrieved from the database.
`o.a.i.applib.` `ObjectPersistedEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `ObjectPersistedEvent.Default` is the concrete implementation that is used.	Broadcast when an object is first saved (inserted) into the database using the `DomainObjectContainer`'s `#persist(…)` method.
`o.a.i.applib.` `ObjectPersistingEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `ObjectPersistingEvent.Default` is the concrete implementation that is used.	Broadcast when an object is about to be saved (inserted) into the database using the `DomainObjectContainer`'s `#persist(…)` method.
`o.a.i.applib.` `ObjectRemovingEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `ObjectRemovingEvent.Default` is the concrete implementation that is used.	Broadcast when an object is about to be deleted from the database using the `DomainObjectContainer`'s `#remove(…)` method.
`o.a.i.applib.` `ObjectUpdatedEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `ObjectUpdatedEvent.Default` is the concrete implementation that is used.	Broadcast when an object has just been updated in the database. This is done either explicitly when the current transaction is flushed using the `DomainObjectContainer`'s `#flush(…)` method, else is done implicitly when the transaction commits at the end of the user request.
`o.a.i.applib.` `ObjectUpdatingEvent`	`o.a.i.core` `services.eventbus` `isis-core-applib`	(abstract class). `ObjectUpdatingEvent.Default` is the concrete implementation that is used.	Broadcast when an object is about to be updated in the database. This is done either explicitly when the current transaction is flushed using the `DomainObjectContainer`'s `#flush(…)` method, else is done implicitly when the transaction commits at the end of the user request.

3.5.1. `AbstractLifecycleEvent`

This class is the superclass for all lifecycle events that are raised by the framework when loading, saving, updating or deleting objects from the database.

Its immediate subclasses are:

3.5.2. `ObjectCreatedEvent`

Subclass of AbstractLifecycleEvent, broadcast when an object is first instantiated using the DomainObjectContainer's #newTransientInstance(…) method.

ObjectCreatedEvent.Default is the concrete implementation that is used.