在web.xml中配置，使用配置类替代springmvc.xml和applicationContext.xml

1、在web.xml配置，让spring mvc在启动的时候，从带有@Configuration注解的类上加载配置，要在Spring MVC中使用基于java的配置，我们需要告诉DispatchServlet和ContextLoaderListener使用AnnotationConfigWebApplicationContext，这是WebApplicationContext的实现类，他会加载java配置类，而不是xml。要实现这种配置，我们可以设置contextClass上下文参数以及DispatcherServlet的初始化参数。如下所示

<?xml version="1.0" encoding="UTF-8"?>

<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">

<!-- 让applicationContext.xml使用java配置 -->

<context-param>

<param-name>contextClass</param-name>

<param-value>
org.springframework.web.context.support.AnnotationConfigWebApplicationContext

</param-value>

</context-param>

<!-- 指定根配置类，相当于applicationContext.xml中的配置 -->

<context-param>

<param-name>contextConfigLocation</param-name>

<param-value>根配置类的全类名</param-value>

</context-param>

<listener>

<listener-class>

org.springframework.web.context.ContextLoaderListener

</listener-class>

</listener>

<!-- 让dispatcherServlet使用java配置 -->

<servlet>

<servlet-name>springmvc</servlet-name>

<servlet-class>

org.springframework.web.servlet.DispatcherServlet

</servlet-class>

<!-- 告诉springmvc.xml使用java配置 -->

<init-param>

<param-name>contextClass</param-name>

<param-value>

org.springframework.web.context.support.AnnotationConfigWebApplicationContext

</param-value>

</init-param>

<!-- 指定dispatcherServlet配置类 -->

<init-param>

<param-name>contextConfigLocation</param-name>

<param-value>

实现了WebMvcConfigurerAdapter的配置类，相当于springmvc.xml

</param-value>

</init-param>

</servlet>

<servlet-mapping>

<servlet-name>springmvc</servlet-name>

<url-pattern>/</url-pattern>

</servlet-mapping>

</web-app>