本文来介绍下InitializingBean接口和DisposableBean接口的作用


文章目录

1.InitializingBean

  该接口的作用是：允许一个bean在它的所有必须属性被BeanFactory设置后，来执行初始化的工作，该接口中只有一个方法，afterPropertiesSet

public interface InitializingBean {

  /**
   * Invoked by the containing {@code BeanFactory} after it has set all bean properties
   * and satisfied {@link BeanFactoryAware}, {@code ApplicationContextAware} etc.
   * <p>This method allows the bean instance to perform validation of its overall
   * configuration and final initialization when all bean properties have been set.
   * @throws Exception in the event of misconfiguration (such as failure to set an
   * essential property) or if initialization fails for any other reason
   */
  void afterPropertiesSet() throws Exception;

}

2.DisposableBean

  该接口的作用是：允许在容器销毁该bean的时候获得一次回调。DisposableBean接口也只规定了一个方法：destroy

public interface DisposableBean {

  /**
   * Invoked by the containing {@code BeanFactory} on destruction of a bean.
   * @throws Exception in case of shutdown errors. Exceptions will get logged
   * but not rethrown to allow other beans to release their resources as well.
   */
  void destroy() throws Exception;

}

3.案例演示

/**
 * 实现InitializingBean和DisposableBean接口
 * @author dengp
 *
 */
public class User implements InitializingBean,DisposableBean{

  private int id;
  
  private String name;
  
  private String beanName;
  
  public User(){
    System.out.println("User 被实例化");
  }

  public int getId() {
    return id;
  }

  public void setId(int id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    System.out.println("设置："+name);
    this.name = name;
  }

  public String getBeanName() {
    return beanName;
  }

  public void setBeanName(String beanName) {
    this.beanName = beanName;
  }
  
  @Override
  public String toString() {
    return "User [id=" + id + ", name=" + name + ", beanName=" + beanName + "]";
  }

  @Override
  public void destroy() throws Exception {
    // TODO Auto-generated method stub
    System.out.println("destory ....");
  }

  @Override
  public void afterPropertiesSet() throws Exception {
    System.out.println("afterPropertiesSet....");
  }
}

配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans 
 http://www.springframework.org/schema/beans/spring-beans.xsd">

  <bean class="com.dpb.pojo.User" id="user" >
    <property name="name" value="波波烤鸭"></property>
  </bean>
  
</beans>

测试代码

@Test
public void test1() {
  ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
  User user = ac.getBean(User.class);
  System.out.println(user);
  ac.registerShutdownHook();
}

输出结果：

User 被实例化
设置：波波烤鸭
afterPropertiesSet....
User [id=0, name=波波烤鸭, beanName=null]
destory ....

  通过输出能够显示spring初始化bean的时候，如果bean实现了InitializingBean接口，会自动调用afterPropertiesSet方法，在bean被销毁的时候如果实现了DisposableBean接口会自动回调destroy方法后然后再销毁