DWR源码学习（一）

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DWR JavaScript Servlet Web Ajax

<?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

<web-app id="dwr">
5

<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

<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

<servlet-mapping>
32

<servlet-name>dwr-invoker</servlet-name>
33

<url-pattern>/dwr/*</url-pattern>
34

</servlet-mapping>
35

</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：

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(

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