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.

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<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.

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<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.

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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.

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<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:

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<?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:

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<?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:

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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

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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.

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<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:

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<?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:

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<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.

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<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>