REST Client

This library is for integration scenario to programmatically invoke the REST API (Restful Objects Viewer) of an Apache Causeway application, using the restfulobjects protocol.

A common use case would be to consume information from some external system, for example uploading a scanned PDF or a representation of an incoming invoice.

Initializing

We create a RestfulClient using a static factory method that accepts a RestfulClientConfig object.

For example:

to create a RestfulClient that authenticates itself using basic auth:

RestfulClient restfulClient = RestfulClient.ofConfig(
        RestfulClientConfig.builder()
            .restfulBaseUrl("localhost:8080")
            .authenticationMode(AuthenticationMode.BASIC)
            .basicAuthUser("xxxx")
            .basicAuthPassword("xxxx")
            .build());

to create a RestfulClient that authenticates itself using OAuth2 (Azure):

RestfulClient restfulClient = RestfulClient.ofConfig(
        RestfulClientConfig.builder()
            .restfulBaseUrl("localhost:8080")
            .authenticationMode(AuthenticationMode.OAUTH2_AZURE)
            .oauthTenantId("xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx")          (1)
            .oauthClientId("xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx")          (2)
            .oauthClientSecret("xxXXx~XXxxXx-XxXX.XxXX.XxxXX-XxxXX~XxxXX")  (3)
            .build());

For the Causeway app being connected to, this will need to be configured appropriately; see Spring Oauth2 extension for more details.

It’s also possible to create a RestfulClient that uses some other arbitrary authentication mechanism:

RestfulClient restfulClient = RestfulClient.ofConfig(
        RestfulClientConfig.builder()                   (1)
            .restfulBaseUrl("localhost:8080")
            .build(),
            new AuthorizationHeaderFactory() {
                @Override
                public String create() {
                    return "some authorization header"; (2)
                }
            });
);

1	No need to provide any authentication details in the `RestfulClientConfig`
2	Used as the value of the `Authorization` HTTP header.

Making a Request

Invocation.Builder request =                                                            (1)
    restfulClient.request("services/customers.CustomerApi/actions/findAll/invoke");     (2)

Response response = request.get();                                                      (3)
//        Response response = request.put(...);                                         (3)
//        Response response = request.post(...);                                        (3)
//        Response response = request.delete();                                         (3)

1	instance of `javax.ws.rs.client.Invocation.Builder`
2	specify the endpoint
3	call appropriately using either HTTP `GET`, `PUT`, `POST` or `DELETE`. The `PUT` and `POST` methods will require an entity body, and all might require additional headers to be set.

Refining the Client

The RestfulClient delegates to an instance of javax.ws.rs.client.Client to actually perform the invocation. The configuration of this underlying Client can be refined by providing a "refining" operator of ClientBuilder, when the RestfulClient is created.

For example, to specify a connection and read timeout:

RestfulClient restfulClient = RestfulClient.ofConfig(
        RestfulClientConfig.builder()
                .restfulBaseUrl("localhost:8080")
                //...                                               (1)
                .build(),
                clientBuilder ->                                    (2)
                clientBuilder.connectTimeout(5, TimeUnit.SECONDS)
                             .readTimeout(2, TimeUnit.SECONDS)
);

1	authentication details omitted
2	instance of `javax.ws.rs.client.ClientBuilder`