Spring之InitializingBean接口和DisposableBean接口介紹

 本文來介紹下InitializingBean接口和DisposableBean接口的作用

文章目錄

   1.InitializingBean

   2.DisposableBean

   3.案例示範

1.InitializingBean

 該接口的作用是：允許一個bean在它的所有必須屬性被BeanFactory設定後，來執行初始化的工作，該接口中隻有一個方法，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

 該接口的作用是：允許在容器銷毀該bean的時候獲得一次回調。DisposableBean接口也隻規定了一個方法：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.案例示範

/**
 * 實作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 被執行個體化");
    }

    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("設定："+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....");
    }
}      

配置檔案

<?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="波波烤鴨"></property>
    </bean>
    
</beans>      

測試代碼

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

輸出結果：

User 被執行個體化
設定：波波烤鴨
afterPropertiesSet....
User [id=0, name=波波烤鴨, beanName=null]
destory ....      

 通過輸出能夠顯示spring初始化bean的時候，如果bean實作了InitializingBean接口，會自動調用afterPropertiesSet方法，在bean被銷毀的時候如果實作了DisposableBean接口會自動回調destroy方法後然後再銷毀