Struts的ActionServlet模拟实现

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Struts

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):