实例详解Spring MVC入门使用

MVC模式(Model-View-Controller)是软件工程中的一种软件架构模式,把软件系统分为三个基本部分：模型(Model),视图(View)和控制器(Controller).通过分层使开发的软件结构更清晰,从而达到开发效率的提高,可维护性和扩展性得到提高.spring提供的MVC框架是在J2EE Web开发中对MVC模式的一个实现,本文通过实例讲解一下Spring MVC 的使用.

先来看一个HTTP request在Spring的MVC框架是怎么被处理的:(图片来源于Spring in Action)

1,DispatcherServlet是Spring MVC的核心,它的本质是一个实现了J2EE标准中定义的HttpServlet,通过在web.xml配置<servlet-mapping>,来实现对request的监听.

[html]  view plain  copy <servlet>       <servlet-name>springTestServlet</servlet-name>       <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>       <load-on-startup>2</load-on-startup>   </servlet>   <servlet-mapping>       <servlet-name>springTestServlet</servlet-name>       <url-pattern>*.do</url-pattern>   </servlet-mapping>   ** 以.do结尾的request都会由springTestServlet来处理. 2,3,当接受到request的时候,DispatcherServlet根据HandlerMapping的配置(HandlerMapping的配置文件默认根据<servlet-name>的值来决定,这里会读取springTestServlet-servlet.xml来获得HandlerMapping的配置信息),调用相应的Controller来对request进行业务处理.

[html]  view plain  copy <bean id="simpleUrlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">       <property name="mappings">           <props>               <prop key="/login.do">loginController</prop>           </props>       </property>   </bean>   <bean id="loginController" class="com.test.spring.mvc.contoller.LoginController">       <property name="sessionForm">           <value>true</value>       </property>       <property name="commandName">           <value>loginCommand</value>       </property>       <property name="commandClass">           <value>com.test.spring.mvc.commands.LoginCommand</value>       </property>       <property name="authenticationService">           <ref bean="authenticationService"/>       </property>       <property name="formView">           <value>login</value>       </property>       <property name="successView">           <value>loginDetail</value>       </property>   </bean>   ** 以login.do结尾的request由loginController来处理.<property name="formView">配置的是Controller接收到HTTP GET请求的时候需要显示的逻辑视图名,本例是显示login.jsp,<property name="successView">配置的是在接收到HTTP POST请求的时候需要显示的逻辑视图名,在本例中即login.jsp提交的时候需要显示名为loginDetail的逻辑视图.

4,Controller进行业务处理之后,返回一个ModelAndView对象.

[java]  view plain  copy return new ModelAndView(getSuccessView(),"loginDetail",loginDetail);   5,6,DispatcherServlet根据ViewResolver的配置(本例是在springTestServlet-servlet.xml文件中配置)将逻辑view转换到真正要显示的View,如JSP等.

[html]  view plain  copy <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">       <property name="viewClass">           <value>org.springframework.web.servlet.view.JstlView</value>       </property>       <property name="prefix">           <value>/jsp/</value>       </property>       <property name="suffix">           <value>.jsp</value>       </property>   </bean>   **其作用是将Controller中返回的ModleAndView解析到具体的资源(JSP文件),如上例中的return new ModelAndView(getSuccessView();按照上面ViewResolver配置,会解析成/jsp/loginDetail.jsp.规则为prefix+ModelAndView的第二个参数+suffix.

示例的完整代码如下:

1web.xml:

[html]  view plain  copy <?xml version="1.0" encoding="UTF-8"?>   <web-app id="WebApp_ID" 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">       <display-name>       prjSpring3</display-name>       <servlet>           <servlet-name>springTestServlet</servlet-name>           <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>           <load-on-startup>2</load-on-startup>       </servlet>       <servlet-mapping>           <servlet-name>springTestServlet</servlet-name>           <url-pattern>*.do</url-pattern>       </servlet-mapping>       <listener>           <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>       </listener>       <listener>           <listener-class>org.springframework.web.context.request.RequestContextListener</listener-class>       </listener>       <context-param>           <param-name>contextConfigLocation</param-name>           <param-value>/WEB-INF/springTest-services.xml</param-value>       </context-param>       <jsp-config>           <taglib>               <taglib-uri>/spring</taglib-uri>               <taglib-location>/WEB-INF/spring.tld</taglib-location>           </taglib>       </jsp-config>   </web-app>   2,springTestServlet-servlet.xml的内容如下:

[html]  view plain  copy <?xml version="1.0" encoding="UTF-8"?>   <beans xmlns="http://www.springframework.org/schema/beans"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">       <bean id="simpleUrlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">           <property name="mappings">               <props>                   <prop key="/login.do">loginController</prop>               </props>           </property>       </bean>       <bean id="loginController" class="com.test.spring.mvc.contoller.LoginController">           <property name="sessionForm">               <value>true</value>           </property>           <property name="commandName">               <value>loginCommand</value>           </property>           <property name="commandClass">               <value>com.test.spring.mvc.commands.LoginCommand</value>           </property>           <property name="authenticationService">               <ref bean="authenticationService"/>           </property>           <property name="formView">               <value>login</value>           </property>           <property name="successView">               <value>loginDetail</value>           </property>       </bean>       <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">           <property name="viewClass">               <value>org.springframework.web.servlet.view.JstlView</value>           </property>           <property name="prefix">               <value>/jsp/</value>           </property>           <property name="suffix">               <value>.jsp</value>           </property>       </bean>   </beans>   3,springTest-services.xml的内容:

 <bean id="authenticationService" class="com.test.spring.mvc.services.AuthenticationService"/>

4,Java代码:

[java]  view plain  copy public class LoginController extends SimpleFormController {       org.springframework.web.servlet.DispatcherServlet t;       protected ModelAndView onSubmit(Object command) throws Exception{                  LoginCommand loginCommand = (LoginCommand) command;           authenticationService.authenticate(loginCommand);           LoginDetail loginDetail = authenticationService.getLoginDetail(loginCommand.getUserId());           return new ModelAndView(getSuccessView(),"loginDetail",loginDetail);       }          private AuthenticationService authenticationService;       public AuthenticationService getAuthenticationService() {           return authenticationService;       }       public void setAuthenticationService(               AuthenticationService authenticationService) {           this.authenticationService = authenticationService;       }       ....   public class LoginCommand {       private String userId;       private String password;       ....   public class LoginDetail {       private String userName;   public class AuthenticationService {               public void authenticate(LoginCommand command) throws Exception{           if(command.getUserId()!= null && command.getUserId().equalsIgnoreCase("test")                    && command.getPassword()!= null && command.getPassword().equalsIgnoreCase("test")){            }else{               throw new Exception("User id is not authenticated");            }       }       public LoginDetail getLoginDetail(String userId){           return new LoginDetail(userId);       }   }             5,JSP文件:放在web-inf的jsp文件夹内

[html]  view plain  copy login.jsp:   <html><head>   <title>Login to Spring Test</title></head>   <body>   <h1>Please enter your userid and password.</h1>   <form method="post" action="login.do">   <table width="95%" bgcolor="f8f8ff" border="0" cellspacing="0" cellpadding="5">   <tr>   <td alignment="right" width="20%">User id:</td>   <td width="20%"><input type="text" name="userId" value="test"></td>   <td width="60%">   </tr>   <tr>   <td alignment="right" width="20%">Password:</td>   <td width="20%"><input type="password" name="password" value="test"></td>   <td width="60%">   </tr>   </table>   <br>   <input type="submit" alignment="center" value="login">   </form>   </body>   </html>      loginDetail.jsp:   <%@ taglib uri="http://java.sun.com/jstl/core_rt" prefix="c"%>    <html><head>   <title>Login to Spring Test</title></head>   <body>   <h1>Login Details:</h1>   <br/>   Login as: <c:out value ="${loginDetail.userName}"/>   <br/>   <a href="/S3/login.do">logout</a>   </body>   </html>   在浏览器的地址栏输入http://localhost:8080/XXX/login.do进入login.jsp页面.

对配置的一些扩充点:

1为HandlerMapping和Controller的配置指定文件名称.

[html]  view plain  copy <servlet>         <servlet-name>springTestServlet</servlet-name>         <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>         <init-param>             <param-name>contextConfigLocation</param-name>             <param-value>classpath*:/xxx.xml</param-value>         </init-param>         <load-on-startup>1</load-on-startup>     </servlet>    

2,加入对MVC注解的支持:

[java]  view plain  copy <?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:context="http://www.springframework.org/schema/context"       xmlns:mvc="http://www.springframework.org/schema/mvc"       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd       http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">       <context:annotation-config />       <context:component-scan base-package="com.test.spring.mvc.contoller" />       <mvc:annotation-driven />      @Controller   public class AnnotationController {       @RequestMapping("annotation.do")       protected void test(HttpServletRequest request,               HttpServletResponse response) throws Exception{                   response.getWriter().println("test Spring MVC annotation");       }   3,注解和SimpleFormController同时使用需要在DispatcherServlet对应的servlet配置文件(本例是springTestServlet-servlet.xml)里面配置: [java]  view plain  copy <bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter"/>      否则会发生下面的异常:   javax.servlet.ServletException: No adapter for handler [com.test.spring.mvc.contoller.LoginController@6ac615]: Does your handler implement a supported interface like Controller?       org.springframework.web.servlet.DispatcherServlet.getHandlerAdapter(DispatcherServlet.java:982)       org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:770)       org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716)       org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:647)       org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:552)       javax.servlet.http.HttpServlet.service(HttpServlet.java:621)       javax.servlet.http.HttpServlet.service(HttpServlet.java:722)   在WEB应用中的context配置文件通过下面的方式load,ContextLoaderListener是一个实现了ServletContextListener的listener, 它能够访问<context-param>而得到配置文件的路径,加载后初始化了一个WebApplicationContext,并且将其作为Attribute放在了servletContext中, 所有可以访问servletContext的地方则可以访问WebApplicationContext. [html]  view plain  copy <listener>       <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>   </listener>   <context-param>       <param-name>contextConfigLocation</param-name>       <param-value>           /WEB-INF/springTest-services.xml,           classpath:conf/jndiDSAppcontext.xml       </param-value>   </context-param>