DWR源码学习

lszone — Fri, 15 Sep 2006 10:48:56 +0800

作者: lszone 链接：http://lszone.javaeye.com/blog/24421 发表时间: 2006年09月15日

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DWR源码学习（一）
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
 2
 3
 4
 5
 6  DWR (Direct Web Remoting)
 7  A demo of how to call Java on the server directly from Javascript on the client
 8
 9  
10    dwr-invoker
11    DWR Servlet
12    Direct Web Remoter Servlet
13    uk.ltd.getahead.dwr.DWRServlet
14    
20    
21      debug
22      true
23    
24    
25      scriptCompressed
26      false
27    
28    1
29  
30
31  
32    dwr-invoker
33    /dwr/*
34  
35
36

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 
 2 
 3 
 4 
 5   DWR - Test Home
 6   
 7   
 8   
 9   
34 
35 
36 
37 .这一部分经过了SERVLET处理：
  
  
  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

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