Struts2的原理和搭建

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今天心情不是很好，梳理一下Struts2来转移注意力。

1.工作流程

当Web容器收到请求（HttpServletRequest）它将请求传递给一个标准的过滤链包括（ActionContextCleanUp）过滤器，然后经过Other filters(SiteMesh ,etc)，接下来需要调用FilterDispatcher核心控制器，然后它调用ActionMapper确定请求哪个Action，ActionMapper返回一个收集Action详细信息的ActionMaping对象。

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接下来FilterDispatcher将控制权委派给ActionProxy,ActionProxy调用配置管理器(ConfigurationManager) 从配置文件中读取配置信息(struts.xml)，然后创建ActionInvocation对象，ActionInvocation在调用Action之前会依次的调用所用配置拦截器（Interceptor N）一旦执行结果返回结果字符串ActionInvocation负责查找结果字符串对应的(Result）然后执行这个Result Result会调用一些模版（JSP）来呈现页面，之后拦截器(Interceptor N)会再被执行(顺序和Action执行之前相反)最后响应(HttpServletResponse)被返回在web.xml中配置的那些过滤器和（核心控制器）（FilterDispatcher）。

2.Demo
项目结构
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web.xml

<?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">    <!-- 定义Struts2的FilterDispathcer的Filter -->    <filter>        <filter-name>struts2</filter-name>        <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>    </filter>    <!-- FilterDispatcher用来初始化struts2并且处理所有的WEB请求。 -->    <filter-mapping>        <filter-name>struts2</filter-name>        <url-pattern>/*</url-pattern>    </filter-mapping> </web-app>

struts2.xml

<?xml version="1.0" encoding="GBK"?><!DOCTYPE struts PUBLIC        "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"        "http://struts.apache.org/dtds/struts-2.0.dtd"><struts>    <!-- 若package加上namespace属性，则jsp页面form的action属性必须加上项目名的路径；           若不加namespace属性，则直接方法名.action即可访问 -->    <package name="struts2" extends="struts-default" namespace="/demo">        <action name="login" class="com.hyan.action.LoginAction" method="login">            <result name="success">/result.jsp</result>        </action>    </package></struts>

LoginAction.java

package com.hyan.action;import com.opensymphony.xwork2.ActionSupport;public class LoginAction extends ActionSupport {    private static final long serialVersionUID = 1L;    private String username;    private String password;    public String login() throws Exception {        return SUCCESS;    }    public String getUsername() {        return username;    }    public void setUsername(String username) {        this.username = username;    }    public String getPassword() {        return password;    }    public void setPassword(String password) {        this.password = password;    }}

index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">    <title>My JSP 'index.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="This is my page">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->  </head>  <body>    This is my JSP page. <br>  </body></html>

<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">    <title>My JSP 'login.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="This is my page">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->  </head>  <body>    <form action="/Struts2Project/demo/login.action" method="post">        账号：<input type="text" name="username" /><br />        密码：<input type="password" name="password" /><br />        <input type="submit" value="submit" />    </form>  </body></html>

result.jsp

<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">    <title>My JSP 'result.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="This is my page">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->  </head>  <body>         账号：${request.username}<br />        密码：${requestScope.password}  </body></html>

3.运行效果
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