Maximum (string) length

The maxLength() attribute applies only to String properties, indicating the maximum number of characters that the user may enter (for example in a text field in the UI). The attribute It is ignored if applied to properties of any other type.

That said, properties are most commonly defined on persistent domain objects (entities), in which case the JDO @Column will in any case need to be specified. Apache Causeway can infer the maxLength semantic directly from the equivalent @Column#length() annotation/attribute.

For example:

import lombok.Getter;
import lombok.Setter;

public class Customer {

    @javax.jdo.annotations.Column(length=30)
    @Getter @Setter
    private String firstName;

    // ...
}

In this case there is therefore no need for the @Property#maxLength attribute.

Non-persistent properties

Of course, not every property is persistent (it could instead be derived), and neither is every domain object an entity (it could be a view model). For these non persistable properties the maxLength attribute is still required.

For example:

public class Customer {

    @javax.jdo.annotation.NotPersistent                         (1)
    @Property(maxLength=100)
    public String getFullName() { /* ... */ }                   (2)
    public void setFullName(String fullName) { /* ... */ }      (3)
    ...
}
1 a non persisted (derived) property
2 implementation would most likely derive full name from constituent parts (eg first name, middle initial, last name)
3 implementation would most likely parse the input and update the constituent parts

See also

This attribute can also be applied to parameters.