spring in action学习笔记十五：配置DispatcherServlet和ContextLoaderListener的几种方式。

　　　在spring in action中论述了：DispatcherServlet和ContextLoaderListener的关系，简言之就是DispatcherServlet是用于加载web层的组件的上下文。ContextLoadListener是加载

其他组件的上下文。

第一种方式：纯注解的方式：

在spring4.0版本以上，倾向用注解的方式配置DispatcherServlet和ContextLoaderListener.配置方式如下：

思路：一个类只要继承AbstractAnnotationConfigDispatcherServletInitializer就会自动配置DispatcherServlet和ContextLoaderListener.

代码如下：

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.core.io.FileSystemResource;
 import org.springframework.web.SpringServletContainerInitializer;
 import org.springframework.web.WebApplicationInitializer;
 import org.springframework.web.bind.annotation.ControllerAdvice;
 import org.springframework.web.bind.annotation.RequestPart;
 import org.springframework.web.multipart.MultipartFile;
 import org.springframework.web.multipart.MultipartResolver;
 import org.springframework.web.multipart.commons.CommonsMultipartResolver;
 import org.springframework.web.multipart.support.StandardServletMultipartResolver;
 import org.springframework.web.servlet.View;
 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.mvc.support.RedirectAttributes;
 import org.springframework.web.servlet.view.BeanNameViewResolver;
 import org.springframework.web.servlet.view.InternalResourceViewResolver;
 import org.springframework.web.servlet.view.JstlView;
 import spittr.web.HomeController;

 import javax.servlet.ServletContainerInitializer;
 import javax.servlet.http.Part;
 import java.io.IOException;

 /**
  * Created by ${秦林森} on 2017/6/12.
  */
 @Configuration
 @EnableWebMvc//这个注解不能少。
 @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.setViewClass(JstlView.class);
         viewResolver.setExposeContextBeansAsAttributes(true);
         return  viewResolver;
     }
     @Override
     public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
         configurer.enable();//configure static content handling.
     }
     @Bean
     public MultipartResolver multipartResolver() throws IOException{
         return  new StandardServletMultipartResolver();
     }
     @Bean
     public MultipartResolver commonsMultipartResolver() throws IOException{
         CommonsMultipartResolver multipartResolver=new CommonsMultipartResolver();
         //setting location where file upload to.
         multipartResolver.setUploadTempDir(new FileSystemResource("com/qls/sen"));
         multipartResolver.setMaxUploadSize(10*1024*1024);
         return multipartResolver;
     }
 }

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 {

 }

 package spittr.config;

 import com.myapp.config.MyFilter;
 import org.springframework.web.filter.CharacterEncodingFilter;
 import org.springframework.web.multipart.commons.CommonsMultipartResolver;
 import org.springframework.web.servlet.DispatcherServlet;
 import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

 import javax.servlet.*;

 /**
  * Created by ${秦林森} on 2017/6/12.
  */
 public class SpittrWebApplicationInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
 //这个方法是配置ContextLoadListener.
     @Override
     protected Class<?>[] getRootConfigClasses() {
         return new Class<?>[]{RootConfig.class};
     }
 //这个方法是配置DispatcherServlet
     @Override
     protected Class<?>[] getServletConfigClasses() {
         //specifiy configuration class
         return new Class<?>[]{WebConfig.class};
     }

     @Override
     protected String[] getServletMappings() {
         return new String[]{"*.do"};//Map DispatcherServlet to
     }
     //文件上传。
     @Override
     protected void customizeRegistration(ServletRegistration.Dynamic registration) {
         registration.setMultipartConfig(new MultipartConfigElement("/tmp/spittr/upload"));
         registration.setLoadOnStartup(1);
         registration.setInitParameter("contextConfigLocation","/WEB-INF/spring/root-context.xml");
     }

     /**
      * 在DispatcherServlet中设置过滤器。
      * @return
      */
     @Override
     protected Filter[] getServletFilters() {
         return new Filter[] {(Filter) new MyFilter(),
         new CharacterEncodingFilter("utf-8")};
     }

     @Override
     public void onStartup(ServletContext servletContext) throws ServletException {
         servletContext.addServlet("m","");
     }

 }

第二种方式：纯配置文件的方式：

 <?xml version="1.0" encoding="UTF-8"?>
 <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
          version="3.1">
     <!--  ContextLoaderListener所加载的bean。相当于第一种方式里面的RootConfig类中包扫描的bean。-->
     <context-param>
         <param-name>contextConfigLocation</param-name>
         <param-value>spring-julysecond.xml</param-value>
     </context-param>
     <listener>
         <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
     </listener>
     <servlet>
         <servlet-name>appServlet</servlet-name>
         <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
         <init-param>
             <!--  DispatcherServlet中加载的配置文件。-->
             <param-name>contextConfigLocation</param-name>
             <param-value>com/config/spring-julythird.xml</param-value>
         </init-param>
         <load-on-startup>1</load-on-startup>
     </servlet>
     <servlet-mapping>
         <servlet-name>appServlet</servlet-name>
         <url-pattern>*.do</url-pattern>
     </servlet-mapping>
 </web-app>

第三种方式：注解和xml配置的混合方式。

在混合方式中必须要让DispatcherServlet和ContextLoadListener知道你在xml中用了注解。用AnnotationConfigWebApplicationContext告诉他俩即可。

代码如下：注意这里的代码是：

web-app用的是:

web-app_2_5.xsd而不是3.1版本的。否则会在

  <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>报错。

 <?xml version="1.0" encoding="UTF-8"?>
 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
          xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

   <!--  告诉ContextLoadListener知道你用注解的方式加载bean。-->
    <context-param>
        <param-name>contextClass</param-name>
        <param-value>org.springframework.web.context.support.AnnotationConfigWebApplicationContext</param-value>
    </context-param>
     <!--  ContextLoaderListener加载RootConfig的bean-->
     <context-param>
         <param-name>contextConfigLocation</param-name>
         <param-value>spittr.config.RootConfig</param-value>
     </context-param>
     <listener>
         <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
     </listener>
     <servlet>
         <servlet-name>appServlet</servlet-name>
         <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextClass</param-name>
            <param-value>org.springframework.web.context.support.AnnotationConfigWebApplicationContext</param-value>
        </init-param>

         <init-param>
             <param-name>contextConfigLocation</param-name>
             <param-value>spittr.config.WebConfig</param-value>
         </init-param>
         <load-on-startup>1</load-on-startup>
     </servlet>
     <servlet-mapping>
         <servlet-name>appServlet</servlet-name>
         <url-pattern>*.do</url-pattern>
     </servlet-mapping>
 </web-app>