与其它web MVC框架一样，Spring的web MVC框架是一个请求驱动的web框架，其设计围绕一个中心的servlet进行， 它能将请求分发给控制器，并提供其它功能帮助web应用开发。然而，Spring的DispatcherServlet 所做的不仅仅是这些，它和Spring的IoC容器完全集成在一起，从而允许你使用Spring的其它功能。
下图展示了Spring Web MVC DispatcherServlet处理请求的流程。 熟悉设计模式的读者可能会发现DispatcherServlet应用了“ Front Controller”模式（很多其他的主流web框架也都用到了该模式）。
注:
Front Controller - 前端控制器 ;
Delegate request: 委托请求 ;
rendering of response :呈现响应 ;
servlet engine ：servlet引擎
Spring Web MVC DispatcherServlet请求处理流程
1.新建web项目。导入spring2.5jar包。采用tomcat6+jdk1.6启动项目。
2.web.xml配置DispatcherServlet
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</init-param>
</servlet>
<!-- url拦截交给DispatcherServlet -->
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern> *.do</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
3.web中加载的applicationContext.xml文件内容如下:
<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
<!-- 配置controller和url的映射关系 -->
<bean id="urlMappging" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
<property name="mappings">
<props>
<prop key="/login.do">loginController</prop>
</props>
</property>
</bean>
<!-- 配置请求的controller业务类 -->
<bean id="loginController" class="com.pb.web.controller.LoginController">
<property name="fromView" value="login"/>
<property name="successView" value="showAccount"/>
</bean>
<!-- 配置jsp作为视图解析器 -->
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/"></property>
<property name="suffix" value=".jsp"/>
</bean>
</beans>
3.com.pb.web.controller.LoginController 类
package com.pb.web.controller;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;
import com.pb.entity.Account;
public class LoginController extends AbstractController {
private String fromView="";
private String successView="";
@Override
protected ModelAndView handleRequestInternal(HttpServletRequest request,
HttpServletResponse response) throws Exception {
//1.获取账户和密码
String cardNo = request.getParameter("cardNo");
String password = request.getParameter("password");
//2.调用业务逻辑层代码判断，在这里弱化controller的处理直接在controller里进行业务判断
Account account = getAccount(cardNo, password);
//3.根据结果返回不同的modelandview
Map<String,Object> model = new HashMap<String,Object>();
if(account!=null){
model.put("account", account);
return new ModelAndView(getSuccessView(),model);
}else{
model.put("message", "用户名密码错误!");
return new ModelAndView(getFromView(),model);
}
}
public Account getAccount(String cardNo,String password){
if(cardNo.equals("123") && password.equals("123")){
Account account = new Account();
account.setCardNo(cardNo);
account.setBalance(88.8f);
return account;
}
return null;
}
public String getFromView() {
return fromView;
}
public void setFromView(String fromView) {
this.fromView = fromView;
}
public void setSuccessView(String successView) {
this.successView = successView;
}
public String getSuccessView() {
return successView;
}
public void setFromview(String successView) {
this.successView = successView;
}
}
4.login.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
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>登录</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>
${message}
<form action="login.do" method="post">
卡号:<input type="text" name="cardNo" value=""/><br/>
密码:<input type="password" name="password" value=""/><br/>
<button type="submit">submit</button>
</form>
</body>
</html>
5.showAccount.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'showAccount.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
卡号:${account.cardNo} <br/>
余额:${account.balance }<br/>
</body>
</html>