@PostConstruct使用姿势

古城微笑少年丶 2022-10-23 05:56 198阅读 0赞

/\*\* 
 \* The PostConstruct annotation is used on a method that needs to be executed 
 \* after dependency injection is done to perform any initialization. This 
 \* method MUST be invoked before the class is put into service. This 
 \* annotation MUST be supported on all classes that support dependency 
 \* injection. The method annotated with PostConstruct MUST be invoked even 
 \* if the class does not request any resources to be injected. Only one 
 \* method can be annotated with this annotation. The method on which the 
 \* PostConstruct annotation is applied MUST fulfill all of the following 
 \* criteria: 
 \* 
 \* <ul> 
 \* <li>The method MUST NOT have any parameters except in the case of 
 \* interceptors in which case it takes an InvocationContext object as 
 \* defined by the Interceptors specification.</li> 
 \* <li>The method defined on an interceptor class MUST HAVE one of the 
 \* following signatures: 
 \* 
 \* void &\#060;METHOD&\#062;(InvocationContext) 
 \* 
 \* Object &\#060;METHOD&\#062;(InvocationContext) throws Exception 
 \* 
 \* Note: A PostConstruct interceptor method must not throw application 
 \* exceptions, but it may be declared to throw checked exceptions including 
 \* the java.lang.Exception if the same interceptor method interposes on 
 \* business or timeout methods in addition to lifecycle events. If a 
 \* PostConstruct interceptor method returns a value, it is ignored by 
 \* the container. 
 \* </li> 
 \* <li>The method defined on a non-interceptor class MUST HAVE the 
 \* following signature: 
 \* 
 \* void &\#060;METHOD&\#062;() 
 \* </li> 
 \* <li>The method on which PostConstruct is applied MAY be public, protected, 
 \* package private or private.</li> 
 \* <li>The method MUST NOT be static except for the application client.</li> 
 \* <li>The method MAY be final.</li> 
 \* <li>If the method throws an unchecked exception the class MUST NOT be put into 
 \* service except in the case of EJBs where the EJB can handle exceptions and 
 \* even recover from them.</li></ul> 
 \* @since Common Annotations 1.0 
 \* @see javax.annotation.PreDestroy 
 \* @see javax.annotation.Resource 
 \*/

1、注解@PostConstruct使用在需要执行一些初始化的方法上，该方法在依赖注入之后被执行。

2、使用该类实例化对象并向外提供服务之前这个方法必须被调用。

3、这个注解可以被所有支持依赖注入的类使用。

4、被@PostConstruct注解的方法必须被调用，即使类没有要求任何资源被注入。

5、类中有且只有一个方法被@PostConstruct注解修饰。

6、被@PostConstruct注解的方法需要遵循以下原则：

*  方法不能有任何参数除非作为拦截器，在那种情况下根据拦截器规范需要定义一个上下文调用对象。

\* <li>The method defined on an interceptor class MUST HAVE one of the 
 \* following signatures: 
 \* 
 \* void &\#060;METHOD&\#062;(InvocationContext) 
 \* 
 \* Object &\#060;METHOD&\#062;(InvocationContext) throws Exception 
 \* 
 \* Note: A PostConstruct interceptor method must not throw application 
 \* exceptions, but it may be declared to throw checked exceptions including 
 \* the java.lang.Exception if the same interceptor method interposes on 
 \* business or timeout methods in addition to lifecycle events. If a 
 \* PostConstruct interceptor method returns a value, it is ignored by 
 \* the container. 
 \* </li> 
 \* <li>The method defined on a non-interceptor class MUST HAVE the 
 \* following signature: 
 \* 
 \* void &\#060;METHOD&\#062;() 
 \* </li> 
 \* <li>The method on which PostConstruct is applied MAY be public, protected, 
 \* package private or private.</li> 
 \* <li>The method MUST NOT be static except for the application client.</li> 
 \* <li>The method MAY be final.</li> 
 \* <li>If the method throws an unchecked exception the class MUST NOT be put into 
 \* service except in the case of EJBs where the EJB can handle exceptions and 
 \* even recover from them.</li></ul> 
 \*/