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/*
 * Copyright 2009 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.user.client.rpc;

import com.google.gwt.core.client.GWT;
import com.google.gwt.http.client.RequestBuilder;
import com.google.gwt.http.client.RequestCallback;

/**
 * This class encapsulates the logic necessary to configure a RequestBuilder for
 * use with an RPC proxy object. Users who wish to alter the specifics of the
 * HTTP requests issued by RPC proxy objects may override the protected
 * doXyz methods and pass an instance of the subclass to
 * {@link ServiceDefTarget#setRpcRequestBuilder}.
 */
public class RpcRequestBuilder {
  /**
   * Used by {@link #doSetContentType}.
   */
  public static final String CONTENT_TYPE_HEADER = "Content-Type";

  /**
   * Used by {@link #doFinish}.
   */
  /*
   * NB: Also used by RpcServlet.
   */
  public static final String MODULE_BASE_HEADER = "X-GWT-Module-Base";

  /**
   * Used by {@link #doFinish}.
   */
  /*
   * NB: Also used by AbstractRemoteServiceServlet.
   */
  public static final String STRONG_NAME_HEADER = "X-GWT-Permutation";

  /**
   * Not exposed directly to the subclass.
   */
  private RequestBuilder builder;

  /**
   * Initialize the RpcRequestBuilder. This method must be called before any of
   * the other methods in this class may be called. Calling create
   * before calling {@link #finish()} will reset the state of the
   * RpcRequestBuilder.
   * 

* This method delegates to {@link #doCreate} to instantiate the * RequestBuilder. * * @param serviceEntryPoint The URL entry point * @return this * @see ServiceDefTarget#setServiceEntryPoint(String) */ public final RpcRequestBuilder create(String serviceEntryPoint) { builder = doCreate(serviceEntryPoint); assert builder != null : "doCreate failed to return a RequestBuilder"; return this; } /** * This method must be called to return the RequestBuilder that the RPC * request will be made with. *

* This method will call {@link #doFinish} before returning the current * RequestBuilder. */ public final RequestBuilder finish() { try { assert builder != null : "Call create() first"; doFinish(builder); return builder; } finally { builder = null; } } /** * Sets the RequestCallback to be used by the RequestBuilder. Delegates to * {@link #doSetCallback}. * * @param callback the RequestCallback to be used by the RequestBuilder * @return this */ public final RpcRequestBuilder setCallback(RequestCallback callback) { assert builder != null : "Call create() first"; doSetCallback(builder, callback); return this; } /** * Sets the MIME content type to be used by the RequestBuilder. Delegates to * {@link #doSetContentType}. * * @param contentType the MIME content type to be used in the request * @return this */ public final RpcRequestBuilder setContentType(String contentType) { assert builder != null : "Call create() first"; doSetContentType(builder, contentType); return this; } /** * Sets the request data to be sent in the request. Delegates to * {@link #doSetRequestData}. * * @param data the data to send * @return this */ public final RpcRequestBuilder setRequestData(String data) { assert builder != null : "Call create() first"; doSetRequestData(builder, data); return this; } /** * Sets the request id of the request. Delegates to {@link #doSetRequestId}. * * @param id the issue number of the request * @return this */ public final RpcRequestBuilder setRequestId(int id) { assert builder != null : "Call create() first"; doSetRequestId(builder, id); return this; } /** * Called by {@link #create} to instantiate the RequestBuilder object. *

* The default implementation creates a POST RequestBuilder with * the given entry point. * * @param serviceEntryPoint the URL to which the request should be issued * @return the RequestBuilder that should be ultimately passed to the * RpcRequestBuilder's caller. */ protected RequestBuilder doCreate(String serviceEntryPoint) { return new RequestBuilder(RequestBuilder.POST, serviceEntryPoint); } /** * Called by {@link #finish()} prior to returning the RequestBuilder to the * caller. *

* The default implementation sets the {@value #STRONG_NAME_HEADER} header to * the value returned by {@link GWT#getPermutationStrongName()}. * * @param rb The RequestBuilder that is currently being configured */ protected void doFinish(RequestBuilder rb) { rb.setHeader(STRONG_NAME_HEADER, GWT.getPermutationStrongName()); rb.setHeader(MODULE_BASE_HEADER, GWT.getModuleBaseURL()); } /** * Called by {@link #setCallback}. *

* The default implementation calls * {@link RequestBuilder#setCallback(RequestCallback)}. * * @param rb the RequestBuilder that is currently being configured * @param callback the user-provided callback */ protected void doSetCallback(RequestBuilder rb, RequestCallback callback) { rb.setCallback(callback); } /** * Called by {@link #setContentType}. *

* The default implementation sets the {@value #CONTENT_TYPE_HEADER} header to * the value specified by contentType by calling * {@link RequestBuilder#setHeader(String, String)}. * * @param rb the RequestBuilder that is currently being configured * @param contentType the desired MIME type of the request's contents */ protected void doSetContentType(RequestBuilder rb, String contentType) { rb.setHeader(CONTENT_TYPE_HEADER, contentType); } /** * Called by {@link #setRequestData}. *

* The default implementation invokes * {@link RequestBuilder#setRequestData(String)}. * * @param rb the RequestBuilder that is currently being configured * @param data the data to send */ protected void doSetRequestData(RequestBuilder rb, String data) { rb.setRequestData(data); } /** * Called by {@link #setRequestId}. *

* The default implementation is a no-op. * * @param rb the RequestBuilder that is currently being configured * @param id the request's issue id */ protected void doSetRequestId(RequestBuilder rb, int id) { } }





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