Struts的ActionServlet模拟实现

Struts中，ActionServlet作为总控Servlet接受请求并转发到各Action，它的原理并不复杂，本文即展示了ActionServlet模拟实现过程。

首先，在Web.xml中配置,让所有url带.go(struts用的do我用go,特意区分一下)的请求都让DispatchServlet处理,DispatchServlet就是ActionServlet模拟实现类.

<? 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-file-list >
         < welcome-file > /web/page/first.jsp </ welcome-file >
     </ welcome-file-list >

     
     < 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的初始化参数,DispatchServlet将用它找到配置文件mockStruts-config.xml,这个文件模拟对应着Struts-config.xml.

DispatchServlet的代码如下:

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;

/**
* 用于分发命令到其它Servlet的总控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 " );

         // 通过ServletContext取得工程的绝对物理路径
        ServletContext sct = getServletContext();
        String realPath = sct.getRealPath( " / " );

         // 通过ServletConfig实例取得初始化参数configFile
        ServletConfig config = this .getServletConfig();
        String mockStrutsCfgFile = config.getInitParameter( " configFile " );

         // 组合配置文件全物理路径
        mockStrutsCfgFile = realPath + mockStrutsCfgFile;

         // 取得请求的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);
        }

         // 取得下一个处理请求的Servlet名
        String servletName = StringUtil.getMatchedString( " /(.*)/(.*)[.] " + patternStr,reqUri);

         // 以Servlet名为基础从设定文件中取得响应的Servlet类名
        ServletFinder finder = new ServletFinder(mockStrutsCfgFile,servletName);
        String servletClass = finder.getServletClass();

         try {
             // 通过反射调用真正的Servlet类进行处理
            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);
    }
}

上面的注释应该说得比较清楚了,DispatchServlet的作用就是解析URI中的ServletName,然后在文件mockStruts-config.xml中以此查找对应的Servlet类,然后用反射生成它的实例处理用户请求.解析的过程借助了正则表达式,查找XML的过程借助了dom4j.

mockStruts-config.xml文件内容如下:

<? xml version="1.0" encoding="GBK" ?>

< servlets >
     
     < servlet >
         < name > login </ name >
         < class > com.sitinspring.action.LoginServlet </ class >
     </ servlet >

     
     < servlet >
         < name > register </ name >
         < class > com.sitinspring.action.RegisterServlet </ class >
     </ servlet >

     
     < servlet >
         < name > ShowPage </ name >
         < class > com.sitinspring.action.ShowPageServlet </ class >
     </ servlet >
</ servlets >

接下来诸个Servlet类处理请求没有什么特别的,你想怎么处理就怎么处理,在下面的Servlet中是找出了提交的所有参数并在后即页面中展示.

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;

/**
* 用于登录处理的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 > ();

         // 取得输入参数并存入哈希表
        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);
    }
}

显示结果的jsp页面代码:

<% @ 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页面 </ 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>参数名: " + key + " 参数值: " + value + " </p> " );
        }
     %>
</ body >
</ html >

发效果之一(通过form提交请求):

转发效果之二(通过链接提交请求):

本文代码下载(请在lib中加入dom4j-1.6.1.jar并载入到工程的库中):
http://www.blogjava.net/Files/sitinspring/MockStruts20080329004955.zip

Struts的ActionServlet模拟实现

Struts的ActionServlet模拟实现

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