在使用spring mvc 构建web应用程序之前，需要了解spring mvc 的请求过程是怎样的，然后记录下如何搭建一个超简单的spring
mvc例子。
1) spring mvc的请求经历
请求由DispatcherServlet分配给控制器(根据处理器映射),在控制器完成处理后，请求会被发送到一个视图(根据viewController解析逻辑视图)
来呈现输出结果。
整理成下图所示：
2)搭建一个简单的spring mvc例子
①创建一个maven工程，其中pom中要有spring相关的坐标：
<spring.version>3.2.1.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.16</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.8.2</version>
</dependency>
<dependency>
<groupId>org.apache.velocity</groupId>
<artifactId>velocity</artifactId>
<version>1.7</version>
</dependency>
<dependency>
<groupId>org.apache.velocity</groupId>
<artifactId>velocity-tools</artifactId>
<version>2.0</version>
<exclusions>
<exclusion>
<groupId>org.apache.struts</groupId>
<artifactId>struts-core</artifactId>
</exclusion>
<exclusion>
<groupId>org.apache.struts</groupId>
<artifactId>struts-taglib</artifactId>
</exclusion>
<exclusion>
<groupId>org.apache.struts</groupId>
<artifactId>struts-tiles</artifactId>
</exclusion>
<exclusion>
<groupId>sslext</groupId>
<artifactId>sslext</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>servletapi</groupId>
<artifactId>servlet-api</artifactId>
<version>2.4</version>
<optional>true</optional>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>jspapi</groupId>
<artifactId>jsp-api</artifactId>
<version>2.0</version>
<optional>true</optional>
</dependency>
</dependencies>
②web.xml中需要配置DispatcherServlet，它是spring mvc前端控制器，请求时是通过它处理的：
<servlet-name>Dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:dispatcher-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
DispatcherServlet是根据一个xml文件来加载其spring上下文的，文件名基于<servlet-name>,因为声明的servlet-name为dispatcher，因此需要有一个dispatcher-servlet.xml。
考虑这种情况：若存在多个xml文件，比如xxx-dao.xml,xx-service.xml这种分层的文件，如何将这些文件一同加载到spring的上下文中呢？这就要通过ContextLoaderListener，它是一个servlet监听器，除了DispatcherServlet创建的上下文外，它能将将其他文件加载到一个spring上下文中。需要在web.xml配置：
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
需要告诉ContextLoaderListener需要加载哪些配置文件，若没有指定的话，上下文加载器会查找/WEB-INF/applicationContext.xml配置文件；若正好声明的spring配置文件名字不是applicationContext.xml,运行的时候是会抛出一个ClassNotFound这个异常的。
所以，配置的web.xml为：
<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">
<display-name>Archetype Created Web Application</display-name>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-config.xml</param-value>
</context-param>
<context-param>
<param-name>log4jConfigLocation</param-name>
<param-value>classpath:log4j.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<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:dispatcher-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<filter>
<filter-name>encodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
<init-param>
<param-name>forceEncoding</param-name>
<param-value>true</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<welcome-file-list>
<welcome-file>/index.html</welcome-file>
</welcome-file-list>
<error-page>
<error-code>404</error-code>
<location>/error/404.html</location>
</error-page>
<error-page>
<error-code>500</error-code>
<location>/error/404.html</location>
</error-page>
<error-page>
<error-code>403</error-code>
<location>/error/404.html</location>
</error-page>
</web-app>
③ 配置文件spring-config.xml和dispatcher-servlet.xml
spring-config.xml:
<context:component-scan base-package="com.test.service.impl" />
<!-- 自动装配Bean -->
<context:annotation-config />
dispatcher-servlet.xml:
<!-- <mvc:resources location="resources/*" mapping="resources/**"/> -->
<!-- 启动spring mvc注解 -->
<mvc:annotation-driven/>
<context:component-scan base-package="com.test.controller"/>
<!--
velocity 配置 -->
<bean id="velocityConfig"
class="org.springframework.web.servlet.view.velocity.VelocityConfigurer">
<property name="resourceLoaderPath" value="/WEB-INF/vm/" />
<property name="velocityProperties">
<props>
<prop key="input.encoding">UTF-8</prop>
<prop key="output.encoding">UTF-8</prop>
<prop key="velocimacro.library">macro/macros.vm</prop>
</props>
</property>
</bean>
<!-- 配置视图解析器，用于解析逻辑视图名-->
<bean id="viewResolver" class="org.springframework.web.servlet.view.velocity.VelocityLayoutViewResolver">
<property name="cache" value="false" />
<property name="prefix" value="" />
<property name="suffix" value=".vm" />
<property name="layoutUrl" value="layout/layout.vm" />
<property name="contentType" value="text/html;charset=UTF-8" />
<property name="exposeSpringMacroHelpers" value="true"/>
<property name="dateToolAttribute" value="dateTool" />
</bean>
④ Controller类：
public class HomeController {
private UserService userService;
@Autowired
public HomeController(UserService userService){
this.userService = userService;
}
//指定请求的路径
@RequestMapping("home.html")
public String showHomePage(Map<String,Object> model){
model.put("count", userService.getUsersCount());
return "home";
}
}
showHomePage对应的请求为：localhost/项目名/home.html
整个项目工程图：