"Spring and Springmvc" Automatically scans for annotation class issues

Respect original source Link: http://blog.csdn.net/u014277445/article/details/52282697

The Spring MVC project typically has two configuration files, Spring-servlet.xml and applicationcontext.xml two profiles, typically with the following configurations:

• <context:annotation-config/>   Its role is to implicitly register with the Spring container

  • Autowiredannota Tionbeanpostprocessor,
  • commonannotationbeanpostprocessor,
  • 　　Persistenceannotationbeanpostprocessor,

  • Requiredannotationbeanpostprocessor

    These 4 beanpostprocessor. The effect is that if you want to use annotations in your program, you must first register the corresponding class for the annotation, as shown in:

  • Dependent Classes-annotations:  
    
    • Commonannotationbeanpostprocessor @Resource, @PostConstruct, @PreDestroy
    • persistenceannotationbeanpostprocessor @PersistenceContext
    • autowiredannotationbeanpostprocessor @Autowired
    • requiredannotationbeanpostprocessor @Required

  Of course you can register yourself:

<bean class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor "/>  <bean class="org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor"/>

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• <context:component-scan base-package="com.*" >

  　　<context:component-scan/>Configuration items not only enable the ability to scan class packages to implement annotation-driven Bean definitions, but also enable annotation-driven auto-injection (that is, implicitly, internally registered Autowiredannotationbeanpostprocessor and Commonannotationbeanpostprocessor), so when used <context:component-scan/> , it can be <context:annotation-config/> removed.

  One interesting question here is whether the scan needs to be configured in two configuration files, and I have done so several tests:

  • This is only configured in Applicationcontext.xml
    <context:component-scan base-package="com.login" />
    Startup is normal, but no requests are intercepted, in short, @controller failure

  • Configuring the above configuration only in Spring-servlet.xml is normal, the request is normal, but the thing fails, that is, it cannot be rolled back.

  • Configure the above information in both Applicationcontext.xml and Spring-servlet.xml
    Start normal, request normal, also the thing is invalid, cannot roll back

  • In Applicationcontext.xml, configure the following in <context:component-scan base-package="com.login" /> Spring-servlet.xml:
    <context:component-scan base-package="com.sohu.login.web" />The start is normal, the request is normal, the things are normal.

    Conclusion: In Spring-servlet.xml, you only need to scan all classes with @controller annotations, and in ApplicationContext you can scan all other annotated classes (you can also filter out classes with @controller annotations). You can also use Context:include-filter and context:exclude-filter to filter annotations that do not require scanning.

• <mvc:annotation-driven />

  It will automatically register defaultannotationhandlermapping with Annotationmethodhandleradapter

Spring and SPRINGMVC automatically scans the annotation class for problems