dwr开发指南---Reverse Ajax

首先：
<servlet>
  <servlet-name>dwr-invoker</servlet-name>
  <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
  <init-param>
    <param-name>activeReverseAjaxEnabled</param-name>
    <param-value>true</param-value>
  </init-param>
  ...
</servlet>
其次，在页面调用：
dwr.engine.setActiveReverseAjax(true);

用java端调用客户端：

        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");
注重客户端的Java调用：
         WebContext wctx = WebContextFactory.get();
        String currentPage = wctx.getCurrentPage();

        ScriptBuffer script = new ScriptBuffer();
        script.appendScript("receiveMessages(")
              .appendData(messages)
              .appendScript(");");

        // Loop over all the users on the current page
        Collection pages = wctx.getScriptSessionsByPage(currentPage);
        for (Iterator it = pages.iterator(); it.hasNext();)
        {
            ScriptSession otherSession = (ScriptSession) it.next();
            otherSession.addScript(script);
        }