Spring automatically scans for conflicting issues with annotation classes

Original address: http://www.blogjava.net/crazycy/archive/2014/07/12/415738.html

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

1. <context:annotation-config/>

Its role is to implicitly register with the Spring container
-Autowiredannotationbeanpostprocessor,
-Commonannotationbeanpostprocessor,
-Persistenceannotationbeanpostprocessor,
-Requiredannotationbeanpostprocessor of these 4 beanpostprocessor.

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

Dependent classes	Annotations
Commonannotationbeanpostprocessor	@Resource, @PostConstruct, @PreDestroy
Persistenceannotationbeanpostprocessor's Bean	@PersistenceContext
Autowiredannotationbeanpostprocessor Bean	@Autowired
Requiredannotationbeanpostprocessor	@Required

Of course, you can also register yourself:

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

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

The <context:component-scan/> configuration item not only enables the ability to scan a class package to implement annotation-driven Bean definitions, but also enables annotation-driven auto-injection (that is, implicitly, internally registered Autowiredannotationbeanpostprocessor and Commonannotationbeanpostprocessor), so when using <context:component-scan/>, You can remove the <context:annotation-config/> from it.

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

(1) Only configured as follows in Applicationcontext.xml

    <context:component-scan base-package= "Com.login"/>

Startup is normal, but no requests are intercepted, in short, @controller failure

(2) Configure the above configuration only in Spring-servlet.xml

Start normal, the request is normal, but the thing is invalid, that is, cannot roll back

(3) Configure the above information in both Applicationcontext.xml and Spring-servlet.xml

Start normal, request normal, also the thing is invalid, cannot roll back

(4) Configure the following in the Applicationcontext.xml

    <context:component-scan base-package= "Com.login"/>

In Spring-servlet.xml, configure the following

    <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).

3. <mvc:annotation-driven/>

It will automatically register defaultannotationhandlermapping with Annotationmethodhandleradapter

4. Use-default-filters= "True" this means that all classes labeled @component under the specified package will be scanned and registered as beans. That is @component's child annotation @service, @Reposity, etc.

Source: http://www.cnblogs.com/fangqi/archive/2012/12/11/2812745.html

Spring automatically scans for conflicting issues with annotation classes