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.do2.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 messages and 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>
