PostConstruct注解
应用场景:当你需要往Bean里注入一个其父类中定义的属性,而你又无法复写父类的属性或属性的setter方法时
public class UserDaoImpl extends HibernateDaoSupport implements UserDao { private SessionFactory mySessionFacotry; @Resource public void setMySessionFacotry(SessionFactory sessionFacotry) { this.mySessionFacotry = sessionFacotry; } @PostConstruct public void injectSessionFactory() { super.setSessionFactory(mySessionFacotry); } ... }
这里通过@PostConstruct,为UserDaoImpl的父类里定义的一个sessionFactory私有属性,注入了我们自己定义的sessionFactory(父类的setSessionFactory方法为final,不可复写),之后我们就可以通过调用 super.getSessionFactory()来访问该属性了。
Java源码:
//Copyright Sun Microsystems Inc. 2004 - 2005. package javax.annotation; import java.lang.annotation.*; import static java.lang.annotation.ElementType.*; import static java.lang.annotation.RetentionPolicy.*; /** * 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 - - The method MUST NOT have any parameters except in the case of EJB * interceptors in which case it takes an InvocationC ontext object as * defined by the EJB specification. * - The return type of the method MUST be void. * - The method MUST NOT throw a checked exception. * - The method on which PostConstruct is applied MAY be public, protected, * package private or private. * - The method MUST NOT be static except for the application client. * - The method MAY be final. * - 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. * @since Common Annotations 1.0 * @see javax.annotation.PreDestroy * @see javax.annotation.Resource */ @Documented @Retention (RUNTIME) @Target(METHOD) public @interface PostConstruct { }
posted on 2016-08-08 11:40 悄悄的来,匆匆的走 阅读(11200) 评论(0) 编辑 收藏 举报