org.apache.juneau.rest

Interface ResponseHandler

All Known Implementing Classes:

DefaultHandler, InputStreamHandler, ReaderHandler, RedirectHandler, StreamableHandler, WritableHandler, ZipFileListResponseHandler

public interface ResponseHandler

Defines the interface for handlers that convert POJOs to appropriate HTTP responses.

The REST Server API uses the concept of registered response handlers for converting objects returned by REST methods or set through RestResponse.setOutput(Object) into appropriate HTTP responses.

Response handlers can be associated with REST resources via the following:

• RestResource.responseHandlers()
• RestContextBuilder.responseHandlers(Class...)
• RestContextBuilder.responseHandlers(ResponseHandler...)

By default, REST resources are registered with the following response handlers:

• DefaultHandler - Serializes POJOs using the Juneau serializer API.
• ReaderHandler - Pipes the output of Readers to the response writer (RestResponse.getWriter()).
• InputStreamHandler - Pipes the output of InputStreams to the response output stream (RestResponse.getOutputStream()).
• RedirectHandler - Handles Redirect objects.
• WritableHandler - Handles Writable objects.
• StreamableHandler - Handles Streamable objects.

Response handlers can be used to process POJOs that cannot normally be handled through Juneau serializers, or because it's simply easier to define response handlers for special cases.

The following example shows how to create a response handler to handle special Foo objects outside the normal Juneau architecture.

@RestResource( path="/example", responseHandlers=FooHandler.class ) public class Example extends RestServlet { @RestMethod(name=GET, path="/") public Foo test1() { return new Foo("123"); } public static class FooHandler implements ResponseHandler { @Override public boolean handle(RestRequest req, RestResponse res, Object output) throws IOException, RestException { if (output instanceof Foo) { Foo foo = (Foo)output; // Set some headers and body content. res.setHeader("Foo-ID", foo.getId()); res.getWriter().write("foo.id=" + foo.getId()); return true; // We handled it. } return false; // We didn't handle it. } } }

See Also:

• Overview > juneau-rest-server > Method Return Types

Method Summary

Modifier and Type	Method and Description
boolean	handle(RestRequest req, RestResponse res, Object output) Process this response if possible.

Method Detail

handle

boolean handle(RestRequest req,
               RestResponse res,
               Object output)
        throws IOException,
               RestException

Process this response if possible. This method should return false if it wasn't able to process the response.

Parameters:

req - The HTTP servlet request.

res - The HTTP servlet response;

output - The POJO returned by the REST method that now needs to be sent to the response.

Returns:

true If this handler handled the response.

Throws:

IOException - If low-level exception occurred on output stream. Results in a HttpServletResponse.SC_INTERNAL_SERVER_ERROR error.

RestException - If some other exception occurred. Can be used to provide an appropriate HTTP response code and message.