如何用Java类配置Spring MVC(不通过web.xml和XML方式)

DispatcherServlet是Spring MVC的核心,按照传统方式, 需要把它配置到web.xml中. 我个人比较不喜欢XML配置方式, XML看起来太累, 冗长繁琐. 还好借助于Servlet 3规范和Spring 3.1的功能增强, 可以采用一种全新的,更简洁的方式配置Spring MVC了. 下面按这种方式一个Hello World的MVC配置.

Step 1:先用eclipse创建一个Maven的WEB工程. pom.xml文件如下:

 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <groupId>ocr</groupId>
   <artifactId>ocr</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>war</packaging>

     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <javaee-api.version>7.0</javaee-api.version>
         <spring.version>4.2.0.RELEASE</spring.version>
         <junit.version>4.12</junit.version>
     </properties>

     <dependencies>
          <dependency>
               <groupId>javax</groupId>
               <artifactId>javaee-api</artifactId>
               <version>${javaee-api.version}</version>
         </dependency>
         <dependency>
                 <groupId>junit</groupId>
                 <artifactId>junit</artifactId>
                 <version>${junit.version}</version>
         </dependency>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-context</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-webmvc</artifactId>
             <version>${spring.version}</version>
         </dependency>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-web</artifactId>
             <version>${spring.version}</version>
         </dependency>

         <dependency>
             <groupId>javax.servlet</groupId>
             <artifactId>jstl</artifactId>
             <version>1.2</version>
         </dependency>

         <dependency>
             <groupId>commons-logging</groupId>
             <artifactId>commons-logging</artifactId>
             <version>1.1.3</version>
         </dependency>
     </dependencies>

     <build>
         <plugins>
             <plugin>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.3</version>
                 <configuration>
                     <source>1.7</source>
                     <target>1.7</target>
                 </configuration>
             </plugin>
             <plugin>
                 <artifactId>maven-war-plugin</artifactId>
                 <version>2.6</version>
                 <configuration>
                     <warSourceDirectory>WebContent</warSourceDirectory>
                     <failOnMissingWebXml>false</failOnMissingWebXml>
                 </configuration>
             </plugin>
         </plugins>
     </build>
 </project>

Step 2: 配置DispatcherServlet. 需要创建一个Web初始化类OcrWebAppInitializer, 继承自AbstractAnnotationConfigDispatcherServletInitializer

 package com.chry.ocr.config;

 import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

 public class OcrWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

     @Override
     protected Class<?>[] getRootConfigClasses() {
         return new Class<?>[] { RootConfig.class };
     }

     @Override
     protected Class<?>[] getServletConfigClasses() {
         return new Class<?>[] { WebConfig.class };        //ָ指定Web配置类
     }

     @Override
     protected String[] getServletMappings() {    //将DispatcherServlet映射到"/"
         return new String[] { "/" };
     }

 }

Step 3: 配置Spring MVC视图解析WebConfig.java, 需要要创建一个类继承自WebMvcConfigurerAdapter

 package com.chry.ocr.config;

 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.web.servlet.ViewResolver;
 import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
 import org.springframework.web.servlet.view.InternalResourceViewResolver;

 @Configuration
 @EnableWebMvc                                //启动SpringMVC
 @ComponentScan("com.chry.ocr.controller")            //启动组件扫描
 public class WebConfig extends WebMvcConfigurerAdapter {

     //配置JSP视图解析器
     @Bean
     public ViewResolver viewResolver() {
         InternalResourceViewResolver resolver = new InternalResourceViewResolver();
         resolver.setPrefix("/WEB-INF/views/");
         resolver.setSuffix(".jsp");
         resolver.setExposeContextBeansAsAttributes(true);
         return resolver;
     }

     //配置静态资源的处理
     @Override
     public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
         configurer.enable();        //对静态资源的请求转发到容器缺省的servlet，而不使用DispatcherServlet
     }

 }

Step 4: 配置RootConfig.java

 package com.chry.ocr.config;

 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.ComponentScan.Filter;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.FilterType;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;

 @Configuration
 @ComponentScan( basePackages={"com.chry.ocr"},
                 excludeFilters = { @Filter(type=FilterType.ANNOTATION,value=EnableWebMvc.class)}
               )

 public class RootConfig {

 }

至此, 传统方式中需要通过web.xml进行配置的东西就已将全部完成有上面三个java类(OcrWebAppInitializer, RootConfig, WebConfig)完成. 可以开始写Controller和页面代码了

Step 5: 编写一个HomeController.java, 它将输出"hello World from Spring MVC"到home.jsp页面

 package com.chry.ocr.controller;

 import static org.springframework.web.bind.annotation.RequestMethod.*;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.servlet.ModelAndView;

 @Controller
 public class HomeController {
     @RequestMapping(value = "/", method=GET)
     public ModelAndView home() {
         String message = "Hello world from Spring MVC";
         return new ModelAndView("home", "message", message);
     }
 }

Step 6: 编写一个jsp页面, 按照我们在视图解析器和Controller里面的配置,放在WEB-INF/views/home.jsp中

 <%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <head>
 <title>Spring MVC Tutorial chry</title>
 <style type="text/css">
 </style>
 </head>
 <body>
     <br>
     <div style='text-align:center;'>
         ${message}
     </div>
 </body>

Step 7: 至此所有工作完成, 使用maven的"clean install"选项进行编译打包后,在执行,访问http://localhost:8080即可. 页面效果和工程结构如下,工程里面没有web.xml