gistfile1.java

import static org.appfuse.gwt.service.client.rest.RestConstants.*;
import com.google.gwt.core.client.GWT;
import com.google.gwt.http.client.Header;
import com.google.gwt.http.client.Request;
import com.google.gwt.http.client.RequestBuilder;
import com.google.gwt.http.client.RequestCallback;
import com.google.gwt.http.client.RequestException;
import com.google.gwt.http.client.Response;

/**
 * This class wraps GWT's RequestBuilder to use a Command Pattern
 * around RequestBuilder and allow chained callbacks (both success and error).
 */
public class RestRequest {

	public enum Method {
		GET,
		POST,
		PUT,
		DELETE
	}

	private RequestBuilder rb;

	public static RestRequest get(String url) {
		return new RestRequest(Method.GET, url);
	}

	public static RestRequest post(String url) {
		return new RestRequest(Method.POST, url);
	}

	protected RestRequest(Method method, String url) {
		this.rb = (method == Method.GET)
				? new RequestBuilder(RequestBuilder.GET, url)
				: new RequestBuilder(RequestBuilder.POST, url);
		setHeader(AcceptHeader.JSON);
	}

	public RestRequest setTimeoutMillis(int timeout) {
		this.rb.setTimeoutMillis(timeout);
		return this;
	}

	public RestRequest setHeader(Header header) {
		rb.setHeader(header.getName(), header.getValue());
		return this;
	}

	public RestRequest setHeader(String header, String value) {
		rb.setHeader(header, value);
		return this;
	}

	public RestRequest setContentType(String value) {
		rb.setHeader(CONTENT_TYPE_HEADER, value);
		return this;
	}

	public RestRequest setRequestData(String requestData) {
		setContentType(RestConstants.HEADER_CONTENT_TYPE_URLENCODED);
		rb.setRequestData(requestData);
		return this;
	}

	public RestRequest setRequestData(String contentType, String requestData) {
		setContentType(contentType);
		rb.setRequestData(requestData);
		return this;
	}

	public RestRequest setRequestData(Representation representation) {
		setContentType(representation.getMimeType());
		rb.setRequestData(representation.getData());
		return this;
	}

	public void execute() {
		build().run();
	}

	public Deferred<Representation> build() {

		if (rb.getTimeoutMillis() == 0) {
			rb.setTimeoutMillis(RestConstants.DEFAULT_TIMEOUT);
		}

		return new AsyncDeferred<Representation>() {

			final AsyncDeferred<Representation> deferred = this;

			@Override
			protected void asyncExecute() {
				rb.setCallback(new RequestCallback() {

					public void onResponseReceived(Request request, Response response) {
						if (response.getStatusCode() >= Response.SC_INTERNAL_SERVER_ERROR) {
							GWT.log("Received status code " + response.getStatusCode(), null);
							onError(request, new ErrorResponseException(response));
						} else {
							Representation representation = getRepresentation(response);
							deferred.onResult(representation);
						}
					}

					public void onError(Request request, Throwable exception) {
						// TODO: Change to use common error-reporting mechanism
						// https://track.chordiant.net/jira/browse/CXDES-16
						deferred.onError(exception);
					}

				});

				try {
					rb.send();
				} catch (RequestException e) {
					onError(e);
				}
			}

		};
	}

	private Representation getRepresentation(Response response) {
		return new Representation(response.getHeader(CONTENT_TYPE_HEADER),
				response.getText(), response.getStatusCode());
	}
}