ActiveMQ example source code file (webmq.js)

This example ActiveMQ source code file (webmq.js) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - ActiveMQ tags/keywords

activexobject, activexobject, error, error, microsoft, msxml, msxml3, msxml3, post, xmldom, xmlhttp, xmlhttp, xmlhttprequest, your

The ActiveMQ webmq.js source code

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

// -----------------
// Original code by Joe Walnes
// -----------------

function Connection(webmqUrl, id) {
    this.messageListeners = new Array()
    this.webmqUrl = webmqUrl
    if (id == null) {
        // TODO use secure random id generation
        id = Math.round(Math.random() * 100000000)
    }
    this.id = id
    // TODO don't start anything until document has finished loading
    var http = this.createHttpControl()
    this.getNextMessageAndLoop(webmqUrl, id, http)
}

Connection.prototype.getNextMessageAndLoop = function(webmqUrl, id, http) {
    http.open("GET", webmqUrl + "?id=" + id + "&xml=true", true)
    var connection = this
    http.onreadystatechange = function() {     
        if (http.readyState == 4) {
            var ok
            try {
                ok = http.status && http.status == 200
            } 
            catch (e) {
                ok = false // sometimes accessing the http.status fields causes errors in firefox. dunno why. -joe
            }
            if (ok) {
                connection.processIncomingMessage(http)
            }
            // why do we have to create a new instance?
            // this is not required on firefox but is on mozilla
            //http.abort()
            http = connection.createHttpControl()
            connection.getNextMessageAndLoop(webmqUrl, id, http)
        }
    }
    http.send(null)
}

Connection.prototype.sendMessage = function(destination, message) {
    // TODO should post via body rather than URL
    // TODO specify destination in message
    var http = this.createHttpControl()
    http.open("POST", this.webmqUrl + "?id=" + this.id + "&body=" + message, true)
    http.send(null)
}

Connection.prototype.processIncomingMessage = function(http) {
    var destination = http.getResponseHeader("destination")
    var message = http.responseXML
    if (message == null) {
        message = http.responseText
    }
    //alert(message.responseText)
    for (var j = 0; j < this.messageListeners.length; j++) {
        var registration = this.messageListeners[j]
        if (registration.matcher(destination)) {
            registration.messageListener(message, destination)
        }
    }
}

Connection.prototype.addMessageListener = function(matcher, messageListener) {
    var wrappedMatcher
    if (matcher.constructor == RegExp) {
        wrappedMatcher = function(destination) { 
            return matcher.test(destination)
        }
    } 
    else if (matcher.constructor == String) {
        wrappedMatcher = function(destination) { 
            return matcher == destination
        }
    } 
    else {
        wrappedMatcher = matcher
    }
    this.messageListeners[this.messageListeners.length] = { matcher: wrappedMatcher, messageListener: messageListener }
}

Connection.prototype.createHttpControl = function() {
    // for details on using XMLHttpRequest see
    // http://webfx.eae.net/dhtml/xmlextras/xmlextras.html
   try {
      if (window.XMLHttpRequest) {
         var req = new XMLHttpRequest()

         // some older versions of Moz did not support the readyState property
         // and the onreadystate event so we patch it!
         if (req.readyState == null) {
            req.readyState = 1
            req.addEventListener("load", function () {
               req.readyState = 4
               if (typeof req.onreadystatechange == "function") {
                  req.onreadystatechange()
               }
            }, false)
         }

         return req
      }
      if (window.ActiveXObject) {
         return new ActiveXObject(this.getControlPrefix() + ".XmlHttp")
      }
   }
   catch (ex) {}
   // fell through
   throw new Error("Your browser does not support XmlHttp objects")
}

Connection.prototype.getControlPrefix = function() {
   if (this.prefix) {
      return this.prefix
   }

   var prefixes = ["MSXML2", "Microsoft", "MSXML", "MSXML3"]
   var o, o2
   for (var i = 0; i < prefixes.length; i++) {
      try {
         // try to create the objects
         o = new ActiveXObject(prefixes[i] + ".XmlHttp")
         o2 = new ActiveXObject(prefixes[i] + ".XmlDom")
         return this.prefix = prefixes[i]
      }
      catch (ex) {}
   }
   throw new Error("Could not find an installed XML parser")
}