DWR群聊实现-第二节

来源：互联网发布：传奇游戏源码是什么编辑：程序博客网时间：2024/05/18 00:23

这里的实现demo来自DWR的官方实例中，我这边主要对其中用到的一些API进行注释。便于后期的学习。

1.实现原理简单剖析

1.web项目中都是通过uri地址作为唯一指定具体页面的途径

譬如说uri：/dwr/chat/java-chat.html 或者/dwr/xxx.do

2.为此dwr可以通过uri获取所有在任何浏览器中打开uri的页面session

这些所有的session表示为一个集合

3.有了这个集合，我们便可以对所有用户所在当前页面进行群发操作。当然这里结合Util类来

执行服务端和客户端的一些js操作。
常用：
1、直接填充内容
2、调用js函数等

这样下面的例子看起来应该简单多了。

2.实现流程：

1.聊天实现类：

public class JavaChat{    /**     * @param text The new message text to add     */    public void addMessage(String text)    {        // Make sure we have a list of the list 10 messages        if (text != null && text.trim().length() > 0)        {            messages.addFirst(new Message(text));            while (messages.size() > 10)            {                messages.removeLast();            }        }        WebContext wctx = WebContextFactory.get();        String currentPage = wctx.getCurrentPage();        // Clear the input box in the browser that kicked off this page only        Util utilThis = new Util(wctx.getScriptSession());        utilThis.setValue("text", "");        // For all the browsers on the current page:        Collection sessions = wctx.getScriptSessionsByPage(currentPage);        Util utilAll = new Util(sessions);        // Clear the list and add in the new set of messages        utilAll.removeAllOptions("chatlog");        utilAll.addOptions("chatlog", messages, "text");    }    /**     * The current set of messages     */    private LinkedList messages = new LinkedList();    /**     * The log stream     */    protected static final Logger log = Logger.getLogger(JavaChat.class);}

2.聊天辅助bean实体：

public class Message{    /**     * @param newtext the new message text     */    public Message(String newtext)    {        text = newtext;        if (text.length() > 256)        {            text = text.substring(0, 256);        }    }    /**     * @return the message id     */    public long getId()    {        return id;    }    /**     * @return the message itself     */    public String getText()    {        return text;    }    /**     * When the message was created     */    private long id = System.currentTimeMillis();    /**     * The text of the message     */    private String text;}

3.dwr配置

<dwr>  <allow> <!-- chat -->    <create creator="new" javascript="JavascriptChat" scope="application">      <param name="class" value="org.getahead.dwrdemo.chat.JavascriptChat"/>    </create>    <create creator="new" javascript="JavaChat" scope="application">      <param name="class" value="org.getahead.dwrdemo.chat.JavaChat"/>    </create>    <convert converter="bean" match="org.getahead.dwrdemo.chat.Message"/>  </allow></dwr>

4.页面调用：

<head>  <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />  <title>DWR Thin Chat Version 2.0</title>  <script type='text/javascript' src='../dwr/engine.js'> </script>  <script type='text/javascript' src='../dwr/interface/JavaChat.js'> </script>  <script type='text/javascript' src='../dwr/util.js'> </script>  <script type="text/javascript">    function sendMessage() {      JavaChat.addMessage(dwr.util.getValue("text"));    }  </script>  <link rel="stylesheet" type="text/css" href="../generic.css" /></head><body onload="dwr.engine.setActiveReverseAjax(true);"><h1>Java Chat</h1><p>This is a very simple chat demo that uses reverse ajax to collect messagesand server-side browser manipulation to update the pages with the results.</p><p>  Your Message:  <input id="text" onkeypress="dwr.util.onReturn(event, sendMessage)"/>  <input type="button" value="Send" onclick="sendMessage()"/></p><hr/><ul id="chatlog" style="list-style-type:none;"></ul></body>