DWR一个外国人实现的很有前途的AJAX框架。
多余的话就不说了，请看DWR的例子程序：
web.xml
1
<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
3
4<web-app id="dwr">
5
6 <display-name>DWR (Direct Web Remoting)</display-name>
7 <description>A demo of how to call Java on the server directly from Javascript on the client</description>
8
9 <servlet>
10 <servlet-name>dwr-invoker</servlet-name>
11 <display-name>DWR Servlet</display-name>
12 <description>Direct Web Remoter Servlet</description>
13 <servlet-class>uk.ltd.getahead.dwr.DWRServlet</servlet-class>
14 <!--
15 <init-param>
16 <param-name>config</param-name>
17 <param-value>WEB-INF/dwr.xml</param-value>
18 </init-param>
19 -->
20 <init-param>
21 <param-name>debug</param-name>
22 <param-value>true</param-value>
23 </init-param>
24 <init-param>
25 <param-name>scriptCompressed</param-name>
26 <param-value>false</param-value>
27 </init-param>
28 <load-on-startup>1</load-on-startup>
29 </servlet>
30
31 <servlet-mapping>
32 <servlet-name>dwr-invoker</servlet-name>
33 <url-pattern>/dwr/*</url-pattern>
34 </servlet-mapping>
35
36</web-app>
servlet（uk.ltd.getahead.dwr.DWRServlet）里：
1 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException
2 {
3 try
4 {
5 builder.set(req, resp, getServletConfig(), getServletContext(), container);
6 ServletLoggingOutput.setExecutionContext(this);
7
8 processor.handle(req, resp);//该方法对所有request路径/dwr/*有效，在引用JS的时候，使用这个路径执行dwr生成的javascript代码
finally
11 {
12 builder.unset();
13 ServletLoggingOutput.unsetExecutionContext();
14 }
15 }
index.html
1 <?xml version="1.0" encoding="ISO-8859-1" ?>
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
3 <html xmlns="http://www.w3.org/1999/xhtml">
4 <head>
5 <title>DWR - Test Home</title>
6 <script type='text/javascript' src='dwr/interface/Test.js'></script>
7 <script type='text/javascript' src='dwr/engine.js'></script>
8 <script type='text/javascript' src='dwr/util.js'></script>
9 <script>
10 function init() {
11 // This turns off the no-javascript message
12 document.getElementById("start").style.display = "none";
13 // This checks for file: URLs and loading problems
14 if (window.DWREngine == null || window.DWRUtil == null) {
15 document.getElementById("file").style.display = "block";
16 return;
17 }
18 // DWR setup
19 DWREngine.setErrorHandler(function(message) { alert(message); });
20 DWREngine.setWarningHandler(function(message) { alert(message); });
21 DWRUtil.useLoadingMessage();
22 // Turn on the generic error div
23 $("error").style.display = "block";
24 // Load a message from the server
25 Test.getInsert(load);
26 }
27
28 function load(data) {
29 $("error").style.display = "none";
30 DWRUtil.setValue("reply", data);
31 $("reply").style.display = "block";
32 }
33 </script>
34 </head>
35
36 <body onload="init()">
37 
.
这一部分经过了SERVLET处理：
<script type='text/javascript' src='dwr/interface/Test.js'></script>
<script type='text/javascript' src='dwr/engine.js'></script>
<script type='text/javascript' src='dwr/util.js'></script>
dwrservlet.doPost方法内processor.handle(req, resp)这个方法如下：
1 public void handle(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException
2 {
3 String pathInfo = req.getPathInfo();
4 String servletPath = req.getServletPath();
5
6 if (nullPathInfoWorkaround && pathInfo == null)
7 {
8 pathInfo = req.getServletPath();
9 servletPath = HtmlConstants.PATH_ROOT;
10 log.debug("Default servlet suspected. pathInfo=" + pathInfo + "; contextPath=" + req.getContextPath() + "; servletPath=" + servletPath); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
11 }
12
13 if (pathInfo == null ||
14 pathInfo.length() == 0 ||
15 pathInfo.equals(HtmlConstants.PATH_ROOT))
16 {
17 resp.sendRedirect(req.getContextPath() + servletPath + HtmlConstants.FILE_INDEX);
18 }
19 else if (pathInfo.startsWith(HtmlConstants.FILE_INDEX))
20 {
21 index.handle(req, resp);
22 }
23 else if (pathInfo.startsWith(HtmlConstants.PATH_TEST))
24 {
25 test.handle(req, resp);
26 }
27 else if (pathInfo.startsWith(HtmlConstants.PATH_INTERFACE))
28 {
29 iface.handle(req, resp);//这个方法是我们要关注的
}
。。。。。。。
}
iface.handle(req, resp);//这个方法是我们要关注的，来自DefaultInterfaceProcessor
1 public void handle(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
2 {
3 String pathinfo = req.getPathInfo();
4 String servletpath = req.getServletPath();
5 if (pathinfo == null)
6 {
7 pathinfo = req.getServletPath();
8 servletpath = HtmlConstants.PATH_ROOT;
9 }
10 String scriptname = pathinfo;
11 scriptname = LocalUtil.replace(scriptname, HtmlConstants.PATH_INTERFACE, HtmlConstants.BLANK);
12 scriptname = LocalUtil.replace(scriptname, HtmlConstants.EXTENSION_JS, HtmlConstants.BLANK);
13 Creator creator = creatorManager.getCreator(scriptname);
14
15 //resp.setContentType("text/javascript");
16 PrintWriter out = resp.getWriter();
17 out.println();
18
19 out.println("function " + scriptname + "() { }"); //从这里开始DWR自动生成javascript
String path = overridePath;
22 if (path == null)
23 {
24 path = req.getContextPath() + servletpath;
25 }
26 out.println(scriptname + "._path = '" + path + "';"); //$NON-NLS-1$ //$NON-NLS-2$
27
28 Method[] methods = creator.getType().getMethods();
29 for (int i = 0; i < methods.length; i++)
30 {
31 Method method = methods[i];
32 String methodName = method.getName();
33
34 // We don't need to check accessControl.getReasonToNotExecute()
35 // because the checks are made by the doExec method, but we do check
36 // if we can display it
37 String reason = accessControl.getReasonToNotDisplay(req, creator, scriptname, method);
38 if (reason != null && !allowImpossibleTests)
39 {
40 continue;
41 }
42
43 // Is it on the list of banned names
44 if (jsutil.isReservedWord(methodName))
45 {
46 continue;
47 }
48
49 out.print('\n');
50 out.print(scriptname + '.' + methodName + " = function("); //$NON-NLS-1$
51 Class[] paramTypes = method.getParameterTypes();
52 for (int j = 0; j < paramTypes.length; j++)
53 {
54 if (!LocalUtil.isServletClass(paramTypes[j]))
55 {
56 out.print("p" + j + ", "); //$NON-NLS-1$ //$NON-NLS-2$
57 }
58 }
59 out.println("callback) {"); //$NON-NLS-1$
60
61 out.print(" DWREngine._execute(" + scriptname + "._path, '" + scriptname + "', '" + methodName + "\', "); //实现javascript调用java内的方法
for (int j = 0; j < paramTypes.length; j++)
63 {
64 if (LocalUtil.isServletClass(paramTypes[j]))
65 {
66 out.print("false, "); //$NON-NLS-1$
67 }
68 else
69 {
70 out.print("p" + j + ", "); //$NON-NLS-1$ //$NON-NLS-2$
71 }
72 }
73 out.println("callback);"); //$NON-NLS-1$
74
75 out.println('}');
76 }
77
78 out.flush();
79 }
DWR例子程序下载地址:http://www.blogjava.net/Files/javajohn/dwr.rar
（待续）