Struts中，ActionServlet作為總控Servlet接受請求并轉發到各Action，它的原理并不復雜，本文即展示了ActionServlet模擬實現過程。
首先，在Web.xml中配置,讓所有url帶.go(struts用的do我用go,特意區分一下)的請求都讓DispatchServlet處理,DispatchServlet就是ActionServlet模擬實現類.
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<!-- welcome.jsp -->
<welcome-file-list>
<welcome-file>/web/page/first.jsp</welcome-file>
</welcome-file-list>
<!-- DispatchServlet -->
<servlet>
<servlet-name>DispatchServlet</servlet-name>
<servlet-class>
com.sitinspring.action.DispatchServlet
</servlet-class>
<init-param>
<description>Configuration File</description>
<param-name>configFile</param-name>
<param-value>web-inf\mockStruts-config.xml</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>DispatchServlet</servlet-name>
<url-pattern>*.go</url-pattern>
</servlet-mapping>
</web-app>
上面指定了DispatchServlet的初始化參數,DispatchServlet將用它找到配置文件mockStruts-config.xml,這個文件模擬對應著Struts-config.xml.
DispatchServlet的代碼如下:
package com.sitinspring.action;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.sitinspring.util.ServletFinder;
import com.sitinspring.util.StringUtil;
/**
* 用于分發命令到其它Servlet的總控Servlet
* @author sitinspring
*
* @date 2008-2-12
*/
public class DispatchServlet extends HttpServlet {
private static final long serialVersionUID = 56890894234786L;
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
request.setCharacterEncoding("UTF-8");
// 通過ServletContext取得工程的絕對物理路徑
ServletContext sct = getServletContext();
String realPath = sct.getRealPath("/");
// 通過ServletConfig實例取得初始化參數configFile
ServletConfig config=this.getServletConfig();
String mockStrutsCfgFile=config.getInitParameter("configFile");
// 組合配置文件全物理路徑
mockStrutsCfgFile=realPath+mockStrutsCfgFile;
// 取得請求的URI
String reqUri=request.getRequestURI();
// 取得模式匹配字符串，即go，do等
String patternStr;
if(reqUri.contains("?")){
patternStr=StringUtil.getMatchedString("([.])(.*)?",reqUri);
}
else{
patternStr=StringUtil.getMatchedString("([.])(.*)$",reqUri);
}
// 取得下一個處理請求的Servlet名
String servletName=StringUtil.getMatchedString("/(.*)/(.*)[.]"+patternStr,reqUri);
// 以Servlet名為基礎從設定文件中取得響應的Servlet類名
ServletFinder finder=new ServletFinder(mockStrutsCfgFile,servletName);
String servletClass=finder.getServletClass();
try {
// 通過反射調用真正的Servlet類進行處理
Class cls=Class.forName(servletClass);
HttpServlet servlet=(HttpServlet)cls.newInstance();
servlet.service(request, response);
} catch (Exception e) {
e.printStackTrace();
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
doPost(request, response);
}
}
上面的注釋應該說得比較清楚了,DispatchServlet的作用就是解析URI中的ServletName,然后在文件mockStruts-config.xml中以此查找對應的Servlet類,然后用反射生成它的實例處理用戶請求.解析的過程借助了正則表達式,查找XML的過程借助了dom4j.
mockStruts-config.xml文件內容如下:
<?xml version="1.0" encoding="GBK"?>
<servlets>
<!-- 處理登錄的Servlet -->
<servlet>
<name>login</name>
<class>com.sitinspring.action.LoginServlet</class>
</servlet>
<!-- 處理注冊的Servlet -->
<servlet>
<name>register</name>
<class>com.sitinspring.action.RegisterServlet</class>
</servlet>
<!-- 處理翻頁的Servlet -->
<servlet>
<name>ShowPage</name>
<class>com.sitinspring.action.ShowPageServlet</class>
</servlet>
</servlets>
接下來諸個Servlet類處理請求沒有什么特別的,你想怎么處理就怎么處理,在下面的Servlet中是找出了提交的所有參數并在后即頁面中展示.
package com.sitinspring.action;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Map;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* 用于登錄處理的Servlet
* @author sitinspring
*
* @date 2008-2-12
*/
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 56890894234786L;
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
request.setCharacterEncoding("UTF-8");
Map<String,String> ht=new Hashtable<String,String>();
// 取得輸入參數并存入哈希表
Enumeration params=request.getParameterNames();
while(params.hasMoreElements()){
String key=(String)params.nextElement();
String value=request.getParameter(key);
ht.put(key, value);
}
request.setAttribute("ht", ht);
RequestDispatcher dispatcher = request.getRequestDispatcher("/web/page/loginResult.jsp");
dispatcher.forward(request, response);
return;
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
doPost(request, response);
}
}
顯示結果的jsp頁面代碼:
<%@ page contentType="text/html; charset=UTF-8"%>
<%@page language="java" import="java.util.Map"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>"MockStruts"-loginResult頁面</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<script src="web/js/ajax.js" type="text/javascript"></script>
<link rel="stylesheet" rev="stylesheet" href="web/css/style.css"
type="text/css" />
</head>
<body>
<%
Map<String,String> ht=(Map<String,String>)request.getAttribute("ht");
for(String key:ht.keySet()){
String value=ht.get(key);
out.print("<p>參數名:"+key+" 參數值:"+value+"</p>");
}
%>
</body>
</html>
轉發效果之一(通過form提交請求):
轉發效果之二(通過鏈接提交請求):
本文代碼下載(請在lib中加入dom4j-1.6.1.jar并載入到工程的庫中):
http://www.aygfsteel.com/Files/sitinspring/MockStruts20080329004955.zip