user/src/com/google/gwt/http/client/Request.java - gwt - Git at Google

 /*
  * Copyright 2008 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.http.client;

 import com.google.gwt.user.client.Timer;
 import com.google.gwt.xhr.client.XMLHttpRequest;

 /**
  * An HTTP request that is waiting for a response. Requests can be queried for
  * their pending status or they can be canceled.
  *
  * <h3>Required Module</h3> Modules that use this class should inherit
  * <code>com.google.gwt.http.HTTP</code>.
  *
  * {@gwt.include
  * com/google/gwt/examples/http/InheritsExample.gwt.xml}
  *
  */
 public class Request {

   /**
    * Creates a {@link Response} instance for the given JavaScript XmlHttpRequest
    * object.
    *
    * @param xmlHttpRequest xmlHttpRequest object for which we need a response
    * @return a {@link Response} object instance
    */
   private static Response createResponse(final XMLHttpRequest xmlHttpRequest) {
     assert (isResponseReady(xmlHttpRequest));
     Response response = new Response() {
       @Override
       public String getHeader(String header) {
         StringValidator.throwIfEmptyOrNull("header", header);

         return xmlHttpRequest.getResponseHeader(header);
       }

       @Override
       public Header[] getHeaders() {
         return Request.getHeaders(xmlHttpRequest);
       }

       @Override
       public String getHeadersAsString() {
         return xmlHttpRequest.getAllResponseHeaders();
       }

       @Override
       public int getStatusCode() {
         return xmlHttpRequest.getStatus();
       }

       @Override
       public String getStatusText() {
         return xmlHttpRequest.getStatusText();
       }

       @Override
       public String getText() {
         return xmlHttpRequest.getResponseText();
       }
     };
     return response;
   }

   /**
    * Returns an array of headers built by parsing the string of headers returned
    * by the JavaScript <code>XmlHttpRequest</code> object.
    *
    * @param xmlHttpRequest
    * @return array of Header items
    */
   private static Header[] getHeaders(XMLHttpRequest xmlHttp) {
     String allHeaders = xmlHttp.getAllResponseHeaders();
     String[] unparsedHeaders = allHeaders.split("\n");
     Header[] parsedHeaders = new Header[unparsedHeaders.length];

     for (int i = 0, n = unparsedHeaders.length; i < n; ++i) {
       String unparsedHeader = unparsedHeaders[i];

       if (unparsedHeader.length() == 0) {
         continue;
       }

       int endOfNameIdx = unparsedHeader.indexOf(':');
       if (endOfNameIdx < 0) {
         continue;
       }

       final String name = unparsedHeader.substring(0, endOfNameIdx).trim();
       final String value = unparsedHeader.substring(endOfNameIdx + 1).trim();
       Header header = new Header() {
         @Override
         public String getName() {
           return name;
         }

         @Override
         public String getValue() {
           return value;
         }

         @Override
         public String toString() {
           return name + " : " + value;
         }
       };

       parsedHeaders[i] = header;
     }

     return parsedHeaders;
   }

   private static boolean isResponseReady(XMLHttpRequest xhr) {
     return xhr.getReadyState() == XMLHttpRequest.DONE;
   }

   /**
    * The number of milliseconds to wait for this HTTP request to complete.
    */
   private final int timeoutMillis;

   /*
    * Timer used to force HTTPRequest timeouts. If the user has not requested a
    * timeout then this field is null.
    */
   private final Timer timer;

   /*
    * JavaScript XmlHttpRequest object that this Java class wraps. This field is
    * not final because we transfer ownership of it to the HTTPResponse object
    * and set this field to null.
    */
   private XMLHttpRequest xmlHttpRequest;

   /**
    * Only used for building a
    * {@link com.google.gwt.user.client.rpc.impl.FailedRequest}.
    */
   protected Request() {
     timeoutMillis = 0;
     xmlHttpRequest = null;
     timer = null;
   }

   /**
    * Constructs an instance of the Request object.
    *
    * @param xmlHttpRequest JavaScript XmlHttpRequest object instance
    * @param timeoutMillis number of milliseconds to wait for a response
    * @param callback callback interface to use for notification
    *
    * @throws IllegalArgumentException if timeoutMillis &lt; 0
    * @throws NullPointerException if xmlHttpRequest, or callback are null
    */
   Request(XMLHttpRequest xmlHttpRequest, int timeoutMillis,
       final RequestCallback callback) {
     if (xmlHttpRequest == null) {
       throw new NullPointerException();
     }

     if (callback == null) {
       throw new NullPointerException();
     }

     if (timeoutMillis < 0) {
       throw new IllegalArgumentException();
     }

     this.timeoutMillis = timeoutMillis;

     this.xmlHttpRequest = xmlHttpRequest;

     if (timeoutMillis > 0) {
       // create and start a Timer
       timer = new Timer() {
         @Override
         public void run() {
           fireOnTimeout(callback);
         }
       };

       timer.schedule(timeoutMillis);
     } else {
       // no Timer required
       timer = null;
     }
   }

   /**
    * Cancels a pending request. If the request has already been canceled or if
    * it has timed out no action is taken.
    */
   public void cancel() {
     /*
      * There is a strange race condition that occurs on Mozilla when you cancel
      * a request while the response is coming in. It appears that in some cases
      * the onreadystatechange handler is still called after the handler function
      * has been deleted and during the call to XmlHttpRequest.abort(). So we
      * null the xmlHttpRequest here and that will prevent the
      * fireOnResponseReceived method from calling the callback function.
      *
      * Setting the onreadystatechange handler to null gives us the correct
      * behavior in Mozilla but crashes IE. That is why we have chosen to fixed
      * this in Java by nulling out our reference to the XmlHttpRequest object.
      */
     if (xmlHttpRequest != null) {
       XMLHttpRequest xmlHttp = xmlHttpRequest;
       xmlHttpRequest = null;

       xmlHttp.clearOnReadyStateChange();
       xmlHttp.abort();

       cancelTimer();
     }
   }

   /**
    * Returns true if this request is waiting for a response.
    *
    * @return true if this request is waiting for a response
    */
   public boolean isPending() {
     if (xmlHttpRequest == null) {
       return false;
     }

     int readyState = xmlHttpRequest.getReadyState();

     /*
      * Because we are doing asynchronous requests it is possible that we can
      * call XmlHttpRequest.send and still have the XmlHttpRequest.getReadyState
      * method return the state as XmlHttpRequest.OPEN. That is why we include
      * open although it is nottechnically true since open implies that the
      * request has not been sent.
      */
     switch (readyState) {
       case XMLHttpRequest.OPENED:
       case XMLHttpRequest.HEADERS_RECEIVED:
       case XMLHttpRequest.LOADING:
         return true;
     }

     return false;
   }

   /*
    * Method called when the JavaScript XmlHttpRequest object's readyState
    * reaches 4 (LOADED).
    */
   void fireOnResponseReceived(RequestCallback callback) {
     if (xmlHttpRequest == null) {
       // the request has timed out at this point
       return;
     }

     cancelTimer();

     /*
      * We cannot use cancel here because it would clear the contents of the
      * JavaScript XmlHttpRequest object so we manually null out our reference to
      * the JavaScriptObject
      */
     final XMLHttpRequest xhr = xmlHttpRequest;
     xmlHttpRequest = null;

     String errorMsg = getBrowserSpecificFailure(xhr);
     if (errorMsg != null) {
       Throwable exception = new RuntimeException(errorMsg);
       callback.onError(this, exception);
     } else {
       Response response = createResponse(xhr);
       callback.onResponseReceived(this, response);
     }
   }

   /*
    * Stops the current HTTPRequest timer if there is one.
    */
   private void cancelTimer() {
     if (timer != null) {
       timer.cancel();
     }
   }

   /*
    * Method called when this request times out.
    *
    * NOTE: this method is called from JSNI
    */
   private void fireOnTimeout(RequestCallback callback) {
     if (xmlHttpRequest == null) {
       // the request has been received at this point
       return;
     }

     cancel();

     callback.onError(this, new RequestTimeoutException(this, timeoutMillis));
   }

   /**
    * Tests if the JavaScript <code>XmlHttpRequest.status</code> property is
    * readable. This can return failure in two different known scenarios:
    *
    * <ol>
    * <li>On Mozilla, after a network error, attempting to read the status code
    * results in an exception being thrown. See <a
    * href="https://bugzilla.mozilla.org/show_bug.cgi?id=238559"
    * >https://bugzilla.mozilla.org/show_bug.cgi?id=238559</a>.</li>
    * <li>On Safari, if the HTTP response does not include any response text. See
    * <a
    * href="http://bugs.webkit.org/show_bug.cgi?id=3810">http://bugs.webkit.org
    * /show_bug.cgi?id=3810</a>.</li>
    * </ol>
    *
    * @param xhr the JavaScript <code>XmlHttpRequest</code> object to test
    * @return a String message containing an error message if the
    *         <code>XmlHttpRequest.status</code> code is unreadable or null if
    *         the status code could be successfully read.
    */
   private native String getBrowserSpecificFailure(XMLHttpRequest xhr) /*-{
     try {
       if (xhr.status === undefined) {
         return "XmlHttpRequest.status == undefined, please see Safari bug " +
                "http://bugs.webkit.org/show_bug.cgi?id=3810 for more details";
       }
       return null;
     } catch (e) {
       return "Unable to read XmlHttpRequest.status; likely causes are a " +
              "networking error or bad cross-domain request. Please see " +
              "https://bugzilla.mozilla.org/show_bug.cgi?id=238559 for more " +
              "details";
     }
   }-*/;
 }
	/*
	* Copyright 2008 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.http.client;

	import com.google.gwt.user.client.Timer;
	import com.google.gwt.xhr.client.XMLHttpRequest;

	/**
	* An HTTP request that is waiting for a response. Requests can be queried for
	* their pending status or they can be canceled.
	*
	* <h3>Required Module</h3> Modules that use this class should inherit
	* <code>com.google.gwt.http.HTTP</code>.
	*
	* {@gwt.include
	* com/google/gwt/examples/http/InheritsExample.gwt.xml}
	*
	*/
	public class Request {

	/**
	* Creates a {@link Response} instance for the given JavaScript XmlHttpRequest
	* object.
	*
	* @param xmlHttpRequest xmlHttpRequest object for which we need a response
	* @return a {@link Response} object instance
	*/
	private static Response createResponse(final XMLHttpRequest xmlHttpRequest) {
	assert (isResponseReady(xmlHttpRequest));
	Response response = new Response() {
	@Override
	public String getHeader(String header) {
	StringValidator.throwIfEmptyOrNull("header", header);

	return xmlHttpRequest.getResponseHeader(header);
	}

	@Override
	public Header[] getHeaders() {
	return Request.getHeaders(xmlHttpRequest);
	}

	@Override
	public String getHeadersAsString() {
	return xmlHttpRequest.getAllResponseHeaders();
	}

	@Override
	public int getStatusCode() {
	return xmlHttpRequest.getStatus();
	}

	@Override
	public String getStatusText() {
	return xmlHttpRequest.getStatusText();
	}

	@Override
	public String getText() {
	return xmlHttpRequest.getResponseText();
	}
	};
	return response;
	}

	/**
	* Returns an array of headers built by parsing the string of headers returned
	* by the JavaScript <code>XmlHttpRequest</code> object.
	*
	* @param xmlHttpRequest
	* @return array of Header items
	*/
	private static Header[] getHeaders(XMLHttpRequest xmlHttp) {
	String allHeaders = xmlHttp.getAllResponseHeaders();
	String[] unparsedHeaders = allHeaders.split("\n");
	Header[] parsedHeaders = new Header[unparsedHeaders.length];

	for (int i = 0, n = unparsedHeaders.length; i < n; ++i) {
	String unparsedHeader = unparsedHeaders[i];

	if (unparsedHeader.length() == 0) {
	continue;
	}

	int endOfNameIdx = unparsedHeader.indexOf(':');
	if (endOfNameIdx < 0) {
	continue;
	}

	final String name = unparsedHeader.substring(0, endOfNameIdx).trim();
	final String value = unparsedHeader.substring(endOfNameIdx + 1).trim();
	Header header = new Header() {
	@Override
	public String getName() {
	return name;
	}

	@Override
	public String getValue() {
	return value;
	}

	@Override
	public String toString() {
	return name + " : " + value;
	}
	};

	parsedHeaders[i] = header;
	}

	return parsedHeaders;
	}

	private static boolean isResponseReady(XMLHttpRequest xhr) {
	return xhr.getReadyState() == XMLHttpRequest.DONE;
	}

	/**
	* The number of milliseconds to wait for this HTTP request to complete.
	*/
	private final int timeoutMillis;

	/*
	* Timer used to force HTTPRequest timeouts. If the user has not requested a
	* timeout then this field is null.
	*/
	private final Timer timer;

	/*
	* JavaScript XmlHttpRequest object that this Java class wraps. This field is
	* not final because we transfer ownership of it to the HTTPResponse object
	* and set this field to null.
	*/
	private XMLHttpRequest xmlHttpRequest;

	/**
	* Only used for building a
	* {@link com.google.gwt.user.client.rpc.impl.FailedRequest}.
	*/
	protected Request() {
	timeoutMillis = 0;
	xmlHttpRequest = null;
	timer = null;
	}

	/**
	* Constructs an instance of the Request object.
	*
	* @param xmlHttpRequest JavaScript XmlHttpRequest object instance
	* @param timeoutMillis number of milliseconds to wait for a response
	* @param callback callback interface to use for notification
	*
	* @throws IllegalArgumentException if timeoutMillis < 0
	* @throws NullPointerException if xmlHttpRequest, or callback are null
	*/
	Request(XMLHttpRequest xmlHttpRequest, int timeoutMillis,
	final RequestCallback callback) {
	if (xmlHttpRequest == null) {
	throw new NullPointerException();
	}

	if (callback == null) {
	throw new NullPointerException();
	}

	if (timeoutMillis < 0) {
	throw new IllegalArgumentException();
	}

	this.timeoutMillis = timeoutMillis;

	this.xmlHttpRequest = xmlHttpRequest;

	if (timeoutMillis > 0) {
	// create and start a Timer
	timer = new Timer() {
	@Override
	public void run() {
	fireOnTimeout(callback);
	}
	};

	timer.schedule(timeoutMillis);
	} else {
	// no Timer required
	timer = null;
	}
	}

	/**
	* Cancels a pending request. If the request has already been canceled or if
	* it has timed out no action is taken.
	*/
	public void cancel() {
	/*
	* There is a strange race condition that occurs on Mozilla when you cancel
	* a request while the response is coming in. It appears that in some cases
	* the onreadystatechange handler is still called after the handler function
	* has been deleted and during the call to XmlHttpRequest.abort(). So we
	* null the xmlHttpRequest here and that will prevent the
	* fireOnResponseReceived method from calling the callback function.
	*
	* Setting the onreadystatechange handler to null gives us the correct
	* behavior in Mozilla but crashes IE. That is why we have chosen to fixed
	* this in Java by nulling out our reference to the XmlHttpRequest object.
	*/
	if (xmlHttpRequest != null) {
	XMLHttpRequest xmlHttp = xmlHttpRequest;
	xmlHttpRequest = null;

	xmlHttp.clearOnReadyStateChange();
	xmlHttp.abort();

	cancelTimer();
	}
	}

	/**
	* Returns true if this request is waiting for a response.
	*
	* @return true if this request is waiting for a response
	*/
	public boolean isPending() {
	if (xmlHttpRequest == null) {
	return false;
	}

	int readyState = xmlHttpRequest.getReadyState();

	/*
	* Because we are doing asynchronous requests it is possible that we can
	* call XmlHttpRequest.send and still have the XmlHttpRequest.getReadyState
	* method return the state as XmlHttpRequest.OPEN. That is why we include
	* open although it is nottechnically true since open implies that the
	* request has not been sent.
	*/
	switch (readyState) {
	case XMLHttpRequest.OPENED:
	case XMLHttpRequest.HEADERS_RECEIVED:
	case XMLHttpRequest.LOADING:
	return true;
	}

	return false;
	}

	/*
	* Method called when the JavaScript XmlHttpRequest object's readyState
	* reaches 4 (LOADED).
	*/
	void fireOnResponseReceived(RequestCallback callback) {
	if (xmlHttpRequest == null) {
	// the request has timed out at this point
	return;
	}

	cancelTimer();

	/*
	* We cannot use cancel here because it would clear the contents of the
	* JavaScript XmlHttpRequest object so we manually null out our reference to
	* the JavaScriptObject
	*/
	final XMLHttpRequest xhr = xmlHttpRequest;
	xmlHttpRequest = null;

	String errorMsg = getBrowserSpecificFailure(xhr);
	if (errorMsg != null) {
	Throwable exception = new RuntimeException(errorMsg);
	callback.onError(this, exception);
	} else {
	Response response = createResponse(xhr);
	callback.onResponseReceived(this, response);
	}
	}

	/*
	* Stops the current HTTPRequest timer if there is one.
	*/
	private void cancelTimer() {
	if (timer != null) {
	timer.cancel();
	}
	}

	/*
	* Method called when this request times out.
	*
	* NOTE: this method is called from JSNI
	*/
	private void fireOnTimeout(RequestCallback callback) {
	if (xmlHttpRequest == null) {
	// the request has been received at this point
	return;
	}

	cancel();

	callback.onError(this, new RequestTimeoutException(this, timeoutMillis));
	}

	/**
	* Tests if the JavaScript <code>XmlHttpRequest.status</code> property is
	* readable. This can return failure in two different known scenarios:
	*
	* <ol>
	* <li>On Mozilla, after a network error, attempting to read the status code
	* results in an exception being thrown. See <a
	* href="https://bugzilla.mozilla.org/show_bug.cgi?id=238559"
	* >https://bugzilla.mozilla.org/show_bug.cgi?id=238559</a>.</li>
	* <li>On Safari, if the HTTP response does not include any response text. See
	* <a
	* href="http://bugs.webkit.org/show_bug.cgi?id=3810">http://bugs.webkit.org
	* /show_bug.cgi?id=3810</a>.</li>
	* </ol>
	*
	* @param xhr the JavaScript <code>XmlHttpRequest</code> object to test
	* @return a String message containing an error message if the
	* <code>XmlHttpRequest.status</code> code is unreadable or null if
	* the status code could be successfully read.
	*/
	private native String getBrowserSpecificFailure(XMLHttpRequest xhr) /*-{
	try {
	if (xhr.status === undefined) {
	return "XmlHttpRequest.status == undefined, please see Safari bug " +
	"http://bugs.webkit.org/show_bug.cgi?id=3810 for more details";
	}
	return null;
	} catch (e) {
	return "Unable to read XmlHttpRequest.status; likely causes are a " +
	"networking error or bad cross-domain request. Please see " +
	"https://bugzilla.mozilla.org/show_bug.cgi?id=238559 for more " +
	"details";
	}
	}-*/;
	}