engine.js

DWR is the way for AJAX implementation

    try {
      batch.req.open(batch.httpMethod, request.url, batch.async);
      try {
        for (prop in batch.headers) {
          var value = batch.headers[prop];
          if (typeof value == "string") batch.req.setRequestHeader(prop, value);
        }
        if (!batch.headers["Content-Type"]) batch.req.setRequestHeader("Content-Type", "text/plain");
      }
      catch (ex) {
        dwr.engine._handleWarning(batch, ex);
      }
      batch.req.send(request.body);
      if (!batch.async) dwr.engine._stateChange(batch);
    }
    catch (ex) {
      dwr.engine._handleError(batch, ex);
    }
  }
  else if (batch.rpcType != dwr.engine.ScriptTag) {
    var idname = batch.isPoll ? "dwr-if-poll-" + batch.map.batchId : "dwr-if-" + batch.map.batchId;
    // Removed htmlfile implementation. Don't expect it to return before v3
    batch.div = document.createElement("div");
    // Add the div to the document first, otherwise IE 6 will ignore onload handler.
    document.body.appendChild(batch.div);
    batch.div.innerHTML = "<iframe src='javascript:void(0)' frameborder='0' style='width:0px;height:0px;border:0;' id='" + idname + "' name='" + idname + "' onload='dwr.engine._iframeLoadingComplete (" + batch.map.batchId + ");'></iframe>";
    batch.document = document;
    batch.iframe = batch.document.getElementById(idname);
    batch.iframe.batch = batch;
    batch.mode = batch.isPoll ? dwr.engine._ModeHtmlPoll : dwr.engine._ModeHtmlCall;
    if (batch.isPoll) dwr.engine._outstandingIFrames.push(batch.iframe);
    request = dwr.engine._constructRequest(batch);
    if (batch.httpMethod == "GET") {
      batch.iframe.setAttribute("src", request.url);
    }
    else {
      batch.form = batch.document.createElement("form");
      batch.form.setAttribute("id", "dwr-form");
      batch.form.setAttribute("action", request.url);
      batch.form.setAttribute("style", "display:none;");
      batch.form.setAttribute("target", idname);
      batch.form.target = idname;
      batch.form.setAttribute("method", batch.httpMethod);
      for (prop in batch.map) {
        var value = batch.map[prop];
        if (typeof value != "function") {
          var formInput = batch.document.createElement("input");
          formInput.setAttribute("type", "hidden");
          formInput.setAttribute("name", prop);
          formInput.setAttribute("value", value);
          batch.form.appendChild(formInput);
        }
      }
      batch.document.body.appendChild(batch.form);
      batch.form.submit();
    }
  }
  else {
    batch.httpMethod = "GET"; // There's no such thing as ScriptTag using POST
    batch.mode = batch.isPoll ? dwr.engine._ModePlainPoll : dwr.engine._ModePlainCall;
    request = dwr.engine._constructRequest(batch);
    batch.script = document.createElement("script");
    batch.script.id = "dwr-st-" + batch.map["c0-id"];
    batch.script.src = request.url;
    document.body.appendChild(batch.script);
  }
};

dwr.engine._ModePlainCall = "/call/plaincall/";
dwr.engine._ModeHtmlCall = "/call/htmlcall/";
dwr.engine._ModePlainPoll = "/call/plainpoll/";
dwr.engine._ModeHtmlPoll = "/call/htmlpoll/";

/** @private Work out what the URL should look like */
dwr.engine._constructRequest = function(batch) {
  // A quick string to help people that use web log analysers
  var request = { url:batch.path + batch.mode, body:null };
  if (batch.isPoll == true) {
    request.url += "ReverseAjax.dwr";
  }
  else if (batch.map.callCount == 1) {
    request.url += batch.map["c0-scriptName"] + "." + batch.map["c0-methodName"] + ".dwr";
  }
  else {
    request.url += "Multiple." + batch.map.callCount + ".dwr";
  }
  // Play nice with url re-writing
  var sessionMatch = location.href.match(/jsessionid=([^?]+)/);
  if (sessionMatch != null) {
    request.url += ";jsessionid=" + sessionMatch[1];
  }

  var prop;
  if (batch.httpMethod == "GET") {
    // Some browsers (Opera/Safari2) seem to fail to convert the callCount value
    // to a string in the loop below so we do it manually here.
    batch.map.callCount = "" + batch.map.callCount;
    request.url += "?";
    for (prop in batch.map) {
      if (typeof batch.map[prop] != "function") {
        request.url += encodeURIComponent(prop) + "=" + encodeURIComponent(batch.map[prop]) + "&";
      }
    }
    request.url = request.url.substring(0, request.url.length - 1);
  }
  else {
    // PERFORMANCE: for iframe mode this is thrown away.
    request.body = "";
    if (document.all && !window.opera) {
      // Use array joining on IE (fastest)
      var buf = [];
      for (prop in batch.map) {
        if (typeof batch.map[prop] != "function") {
          buf.push(prop + "=" + batch.map[prop] + dwr.engine._postSeperator);
        }
      }
      request.body = buf.join("");
    }
    else {
      // Use string concat on other browsers (fastest)
      for (prop in batch.map) {
        if (typeof batch.map[prop] != "function") {
          request.body += prop + "=" + batch.map[prop] + dwr.engine._postSeperator;
        }
      }
    }
    request.body = dwr.engine._contentRewriteHandler(request.body);
  }
  request.url = dwr.engine._urlRewriteHandler(request.url);
  return request;
};

/** @private Called by XMLHttpRequest to indicate that something has happened */
dwr.engine._stateChange = function(batch) {
  var toEval;

  if (batch.completed) {
    dwr.engine._debug("Error: _stateChange() with batch.completed");
    return;
  }

  var req = batch.req;
  try {
    if (req.readyState != 4) return;
  }
  catch (ex) {
    dwr.engine._handleWarning(batch, ex);
    // It's broken - clear up and forget this call
    dwr.engine._clearUp(batch);
    return;
  }

  if (dwr.engine._unloading) {
    dwr.engine._debug("Ignoring reply from server as page is unloading.");
    return;
  }
  
  try {
    var reply = req.responseText;
    reply = dwr.engine._replyRewriteHandler(reply);
    var status = req.status; // causes Mozilla to except on page moves

    if (reply == null || reply == "") {
      dwr.engine._handleWarning(batch, { name:"dwr.engine.missingData", message:"No data received from server" });
    }
    else if (status != 200) {
      dwr.engine._handleError(batch, { name:"dwr.engine.http." + status, message:req.statusText });
    }
    else {
      var contentType = req.getResponseHeader("Content-Type");
      if (!contentType.match(/^text\/plain/) && !contentType.match(/^text\/javascript/)) {
        if (contentType.match(/^text\/html/) && typeof batch.textHtmlHandler == "function") {
          batch.textHtmlHandler({ status:status, responseText:reply, contentType:contentType });
        }
        else {
          dwr.engine._handleWarning(batch, { name:"dwr.engine.invalidMimeType", message:"Invalid content type: '" + contentType + "'" });
        }
      }
      else {
        // Comet replies might have already partially executed
        if (batch.isPoll && batch.map.partialResponse == dwr.engine._partialResponseYes) {
          dwr.engine._processCometResponse(reply, batch);
        }
        else {
          if (reply.search("//#DWR") == -1) {
            dwr.engine._handleWarning(batch, { name:"dwr.engine.invalidReply", message:"Invalid reply from server" });
          }
          else {
            toEval = reply;
          }
        }
      }
    }
  }
  catch (ex) {
    dwr.engine._handleWarning(batch, ex);
  }

  dwr.engine._callPostHooks(batch);

  // Outside of the try/catch so errors propogate normally:
  dwr.engine._receivedBatch = batch;
  if (toEval != null) toEval = toEval.replace(dwr.engine._scriptTagProtection, "");
  dwr.engine._eval(toEval);
  dwr.engine._receivedBatch = null;
  dwr.engine._validateBatch(batch);
  if (!batch.completed) dwr.engine._clearUp(batch);
};

/**
 * @private This function is invoked when a batch reply is received.
 * It checks that there is a response for every call in the batch. Otherwise,
 * an error will be signaled (a call without a response indicates that the 
 * server failed to send complete batch response). 
 */
dwr.engine._validateBatch = function(batch) {
  // If some call left unreplied, report an error.
  if (!batch.completed) {
    for (var i = 0; i < batch.map.callCount; i++) {
      if (batch.handlers[i] != null) {
        dwr.engine._handleWarning(batch, { name:"dwr.engine.incompleteReply", message:"Incomplete reply from server" });
        break;
      }
    }
  }
}

/** @private Called from iframe onload, check batch using batch-id */
dwr.engine._iframeLoadingComplete = function(batchId) {
  // dwr.engine._checkCometPoll();
  var batch = dwr.engine._batches[batchId];
  if (batch) dwr.engine._validateBatch(batch);
}

/** @private Called by the server: Execute a callback */
dwr.engine._remoteHandleCallback = function(batchId, callId, reply) {
  var batch = dwr.engine._batches[batchId];
  if (batch == null) {
    dwr.engine._debug("Warning: batch == null in remoteHandleCallback for batchId=" + batchId, true);
    return;
  }
  // Error handlers inside here indicate an error that is nothing to do
  // with DWR so we handle them differently.
  try {
    var handlers = batch.handlers[callId];
    batch.handlers[callId] = null;
    if (!handlers) {
      dwr.engine._debug("Warning: Missing handlers. callId=" + callId, true);
    }
    else if (typeof handlers.callback == "function") handlers.callback(reply);
  }
  catch (ex) {
    dwr.engine._handleError(batch, ex);
  }
};

/** @private Called by the server: Handle an exception for a call */
dwr.engine._remoteHandleException = function(batchId, callId, ex) {
  var batch = dwr.engine._batches[batchId];
  if (batch == null) { dwr.engine._debug("Warning: null batch in remoteHandleException", true); return; }
  var handlers = batch.handlers[callId];
  batch.handlers[callId] = null;
  if (handlers == null) { dwr.engine._debug("Warning: null handlers in remoteHandleException", true); return; }
  if (ex.message == undefined) ex.message = "";
  if (typeof handlers.exceptionHandler == "function") handlers.exceptionHandler(ex.message, ex);
  else if (typeof batch.errorHandler == "function") batch.errorHandler(ex.message, ex);
};

/** @private Called by the server: The whole batch is broken */
dwr.engine._remoteHandleBatchException = function(ex, batchId) {
  var searchBatch = (dwr.engine._receivedBatch == null && batchId != null);
  if (searchBatch) {
    dwr.engine._receivedBatch = dwr.engine._batches[batchId];
  }
  if (ex.message == undefined) ex.message = "";
  dwr.engine._handleError(dwr.engine._receivedBatch, ex);
  if (searchBatch) {
    dwr.engine._receivedBatch = null;
    dwr.engine._clearUp(dwr.engine._batches[batchId]);
  }
};

/** @private Called by the server: Reverse ajax should not be used */
dwr.engine._remotePollCometDisabled = function(ex, batchId) {
  dwr.engine.setActiveReverseAjax(false);
  var searchBatch = (dwr.engine._receivedBatch == null && batchId != null);
  if (searchBatch) {
    dwr.engine._receivedBatch = dwr.engine._batches[batchId];
  }
  if (ex.message == undefined) ex.message = "";
  dwr.engine._handleError(dwr.engine._receivedBatch, ex);
  if (searchBatch) {
    dwr.engine._receivedBatch = null;
    dwr.engine._clearUp(dwr.engine._batches[batchId]);
  }
};

/** @private Called by the server: An IFrame reply is about to start */
dwr.engine._remoteBeginIFrameResponse = function(iframe, batchId) {
  if (iframe != null) dwr.engine._receivedBatch = iframe.batch;
  dwr.engine._callPostHooks(dwr.engine._receivedBatch);
};

/** @private Called by the server: An IFrame reply is just completing */
dwr.engine._remoteEndIFrameResponse = function(batchId) {
  dwr.engine._clearUp(dwr.engine._receivedBatch);
  dwr.engine._receivedBatch = null;
};

/** @private This is a hack to make the context be this window */
dwr.engine._eval = function(script) {
  if (script == null) return null;
  if (script == "") { dwr.engine._debug("Warning: blank script", true); return null; }
  // dwr.engine._debug("Exec: [" + script + "]", true);
  return eval(script);
};

/** @private Called as a result of a request timeout */
dwr.engine._abortRequest = function(batch) {
  if (batch && !batch.completed) {
    dwr.engine._clearUp(batch);
    if (batch.req) batch.req.abort();
    dwr.engine._handleError(batch, { name:"dwr.engine.timeout", message:"Timeout" });
  }
};

/** @private call all the post hooks for a batch */
dwr.engine._callPostHooks = function(batch) {
  if (batch.postHooks) {
    for (var i = 0; i < batch.postHooks.length; i++) {
      batch.postHooks[i]();
    }