Multiple response types with same REST GET?

Question

I want to create a REST service that can return either JSON or XML. What request parameter do I set in the request to request a certain mime type? I know how to set it in the response, but there must be a way to request a certain one. Currently I do it in the URL

restServlet/engine/2WS2345

jsonServlet/engine/2WS2345

This gets me json or xml. But I thought I read that there is a parameter to set in the request. I am using JAVA...

Answer 1

You can do this with Restlet using annotations in your code and either let the content-negotiation operate depending on the user-agent's Accept header or specify the extension in the URI (using Restlet's TunnelService and MetadataService). Here is an example (based on Restlet 2):

public class TestApplication extends Application {
    public static class TestResource extends ServerResource {
        @Get("txt")
        public Representation toText() {
            return new StringRepresentation("Hello!",
                MediaType.TEXT_PLAIN);
        }

        @Get("xml")
        public Representation toXml() {
            return new StringRepresentation("<test>Hello</test>",
                MediaType.APPLICATION_XML);
        }
    }

    @Override
    public synchronized Restlet createInboundRoot() {
        getTunnelService().setEnabled(true);
        getTunnelService().setExtensionsTunnel(true);
        Router router = new Router();
        router.attachDefault(TestResource.class);
        return router;
    }

    public static void main(String[] args) throws Exception {
        Component component = new Component();
        component.getServers().add(Protocol.HTTP, 8182);
        component.getDefaultHost().attachDefault(new TestApplication());
        component.start();
    }
}

Content-negotiation works via the Accept header:

• curl -H "Accept: text/plain" http://localhost:8182/test returns Hello!
• curl -H "Accept: application/xml" http://localhost:8182/test returns <test>Hello</test>

It also works via the extension (thanks to getTunnelService().setExtensionsTunnel(true)):

• curl http://localhost:8182/test.txt returns Hello!
• curl http://localhost:8182/test.xml returns <test>Hello</test>

There's a default list of extension to media-type mapping, but this can be configured via the MetadataService.