spring in action 学习笔记十四：用纯注解的方式实现spring mvc

　　　　在讲用纯注解的方式实现springmvc之前先介绍一个类：AbstractAnnotationDispatcherServletInitializer.这个类的作用是：任何一个类继承AbstractAnnotationDispatcherServletInitializer,将会自动的被用为配置DispatcherServlet,以及在DispatcherServlet中的的spring容器（如：spring-servlet.xml）文件。

spring in action的描述是：any class that extends AbstractAnnotationDispatcherServletInitializer will automatically be used to configure DispatcherServlet and the Spring Application context in the application's servlet context.

AbstractAnnotationDispatcherServlet的代码如下：

 /*
  * Copyright 2002-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package org.springframework.web.servlet.support;

 import org.springframework.util.ObjectUtils;
 import org.springframework.web.context.WebApplicationContext;
 import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;

 /**
  * Base class for {@link org.springframework.web.WebApplicationInitializer}
  * implementations that register a
  * {@link org.springframework.web.servlet.DispatcherServlet DispatcherServlet}
  * configured with annotated classes, e.g. Spring's
  * {@link org.springframework.context.annotation.Configuration @Configuration} classes.
  *
  * <p>Concrete implementations are required to implement {@link #getRootConfigClasses()}
  * and {@link #getServletConfigClasses()} as well as {@link #getServletMappings()}.
  * Further template and customization methods are provided by
  * {@link AbstractDispatcherServletInitializer}.
  *
  * <p>This is the preferred approach for applications that use Java-based
  * Spring configuration.
  *
  * @author Arjen Poutsma
  * @author Chris Beams
  * @since 3.2
  */
 public abstract class AbstractAnnotationConfigDispatcherServletInitializer
         extends AbstractDispatcherServletInitializer {

     /**
      * {@inheritDoc}
      * <p>This implementation creates an {@link AnnotationConfigWebApplicationContext},
      * providing it the annotated classes returned by {@link #getRootConfigClasses()}.
      * Returns {@code null} if {@link #getRootConfigClasses()} returns {@code null}.
      */
     @Override
     protected WebApplicationContext createRootApplicationContext() {
         Class<?>[] configClasses = getRootConfigClasses();
         if (!ObjectUtils.isEmpty(configClasses)) {
             AnnotationConfigWebApplicationContext rootAppContext = new AnnotationConfigWebApplicationContext();
             rootAppContext.register(configClasses);
             return rootAppContext;
         }
         else {
             return null;
         }
     }

     /**
      * {@inheritDoc}
      * <p>This implementation creates an {@link AnnotationConfigWebApplicationContext},
      * providing it the annotated classes returned by {@link #getServletConfigClasses()}.
      */
     @Override
     protected WebApplicationContext createServletApplicationContext() {
         AnnotationConfigWebApplicationContext servletAppContext = new AnnotationConfigWebApplicationContext();
         Class<?>[] configClasses = getServletConfigClasses();
         if (!ObjectUtils.isEmpty(configClasses)) {
             servletAppContext.register(configClasses);
         }
         return servletAppContext;
     }

     /**
      * Specify {@link org.springframework.context.annotation.Configuration @Configuration}
      * and/or {@link org.springframework.stereotype.Component @Component} classes to be
      * provided to the {@linkplain #createRootApplicationContext() root application context}.
      * @return the configuration classes for the root application context, or {@code null}
      * if creation and registration of a root context is not desired
      */
     protected abstract Class<?>[] getRootConfigClasses();

     /**
      * Specify {@link org.springframework.context.annotation.Configuration @Configuration}
      * and/or {@link org.springframework.stereotype.Component @Component} classes to be
      * provided to the {@linkplain #createServletApplicationContext() dispatcher servlet
      * application context}.
      * @return the configuration classes for the dispatcher servlet application context or
      * {@code null} if all configuration is specified through root config classes.
      */
     protected abstract Class<?>[] getServletConfigClasses();

 }

案例的目录结构如下图所示：

RootConfig的代码如下：

 package spittr.config;

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

 /**
  * Created by ${秦林森} on 2017/6/12.
  */
 @Configuration
 /**
  * excludeFilters是指明不被@ComponentScan扫描的类型
  */
 @ComponentScan(basePackages = {"spittr"},excludeFilters = {@ComponentScan.Filter(type = FilterType.ANNOTATION,value = EnableWebMvc.class)})

 public class RootConfig {

 }

WebConfig的代码如下：

 package spittr.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.BeanNameViewResolver;
 import org.springframework.web.servlet.view.InternalResourceViewResolver;
 import spittr.web.HomeController;

 /**
  * Created by ${秦林森} on 2017/6/12.
  */
 @Configuration
 @EnableWebMvc
 @ComponentScan(basePackages = {"spittr.web"})
 public class WebConfig extends WebMvcConfigurerAdapter{
     @Bean
     public ViewResolver viewResolver(){
         InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
         //设置前缀
         viewResolver.setPrefix("/WEB-INF/views/");
         //设置后缀
         viewResolver.setSuffix(".jsp");
         viewResolver.setExposeContextBeansAsAttributes(true);
         return  viewResolver;
     }
     @Override
     public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
         configurer.enable();//configure static content handling.
     }

 }

 package spittr.config;

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

 /**
  * Created by ${秦林森} on 2017/6/12.
  */
 public class SpittrWebApplicationInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

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

     @Override
     protected Class<?>[] getServletConfigClasses() {
         //specifiy configuration class
         return new Class<?>[]{WebConfig.class};
     }

     @Override
     protected String[] getServletMappings() {
         return new String[]{"*.do"};//Map DispatcherServlet to
     }
 }

HomeController的代码如下：

 package spittr.web;

 import org.springframework.stereotype.Controller;
 import org.springframework.web.WebApplicationInitializer;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;

 /**
  * Created by ${秦林森} on 2017/6/12.
  */
 @Controller
 @RequestMapping(value = "/people")
 public class HomeController {
     @RequestMapping(value = "/home.do",method = RequestMethod.GET)
     public  String home(){
         return  "home";
     }
 }

home.jsp的代码如下：

 <%--
   Created by IntelliJ IDEA.
   User: Administrator
   Date: 2017/6/12
   Time: 16:25
   To change this template use File | Settings | File Templates.
 --%>
 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 <html>
 <head>
     <title>spittr</title>
 </head>
 <body>
     welcome to china ,one of the ancient civilized countries.
 </body>
 </html>

注意我这个项目的web应用名设置为该项目名。

启动tomcat 输入：http://localhost:8090/spring20170602/people/home.do

访问结果如下图所示: