applicationContext.xml和dispatcher-servlet.xml的区别

  在SpringMVC项目中我们一般会引入applicationContext.xml和dispatcher-servlet.xml两个配置文件,这两个配置文件具体的区别是什么呢?

  Spring 官方文档介绍如下:

  Spring lets you define multiple contexts in a parent-child hierarchy.  
  The applicationContext.xml defines the beans for the "root webapp context", i.e. the context associated with the webapp.   The spring-servlet.xml (or whatever else you call it) defines the beans for one servlet‘s app context.
There can be many of these in a webapp, one per Spring servlet (e.g. spring1-servlet.xml for servlet spring1, spring2-servlet.xml
for servlet spring2).   Beans in spring-servlet.xml can reference beans in applicationContext.xml, but not vice versa.   All Spring MVC controllers must go in the spring-servlet.xml context.   In most simple cases, the applicationContext.xml context is unnecessary. It is generally used to contain beans that are shared
between all servlets in a webapp. If you only have one servlet, then there‘s not really much point, unless you have a specific use for it.

  可见, applicationContext.xml 和 dispatch-servlet.xml形成了两个父子关系的上下文。

  1) 一个bean如果在两个文件中都被定义了(比如两个文件中都定义了component scan扫描相同的package), spring会在application context和 servlet context中都生成一个实例,他们处于不同的上下文空间中,他们的行为方式是有可能不一样的。

  2) 如果在application context和 servlet context中都存在同一个 @Service 的实例, controller(在servlet context中) 通过 @Resource引用时, 会优先选择servlet context中的实例。

  3)servlet context可以引用application context里的实例,反之不可以。

  4)多个servlet共享application context里的实例

  5)在applicationContext和dispatcher-servlet定义的bean最好不要重复,dispatcher-servlet最好只扫描@controler,applicationContext扫描其它

     dispatcher-servlet.xml

<context:component-scan base-package="com.test.controller" use-default-filters="false">
  <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller" />
</context:component-scan>

    applicationContext.xml

<context:component-scan base-package="com.test" use-default-filters="true">
  <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller" />
</context:component-scan>

    注:

      use-default-filters用来指示是否自动扫描带有@Component、@Repository、@Service和@Controller的类。默认为true,即默认扫描

      <context:include-filter/>子标签是用来添加扫描注解

      <context:exclude-filter/>子标签是用来排除扫描注解

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  ApplicationContext.xml  是spring 全局配置文件,用来控制spring 特性的

  dispatcher-servlet.xml 是spring mvc里面的,控制器、拦截uri转发view

  使用applicationContext.xml文件时是需要在web.xml中添加listener的:

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>
      classpath:applicationContext.xml
    </param-value>
</context-param>
<listener>
  <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

 

applicationContext.xml和dispatcher-servlet.xml的区别

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