详解Spring中Bean后置处理器(BeanPostProcessor)的使用

/**
 * 观察bean周期执行流程
 */
public class User {
    String name;
    int age;

    //无参构造方法
    public User() {
        System.out.println("这是无参构造方法");
    }

    //setter方法
    public void setName(String name) {
        System.out.println("这是setter注入name");
        this.name = name;
    }

    public void setAge(int age) {
        System.out.println("这是setter注入age");
        this.age = age;
    }

    //初始化回调方法
    public void init() throws Exception {
        System.out.println("这是初始化回调方法");
    }

    //销毁回调方法
    public void destroy() throws Exception {
        System.out.println("这是销毁回调方法");
    }

    //toString方法
    @Override
    public String toString() {
        return "User{" +
            "name='" + name + '\'' +
            ", age=" + age +
            '}';
    }
}

/**
 * Spring Bean后置处理器
 */
public class PostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println(beanName+"正在执行预初始化方法");
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println(beanName+"正在执行后初始化方法");
        return bean;
    }
}

<!--添加user bean-->
<bean id="user" class="com.bighorn.pojo.User" init-method="init" destroy-method="destroy">
    <property name="name" value="bighorn"/>
    <property name="age" value="18"/>
</bean>
<!-- 注册后置处理器 -->
<bean id="postProcessor" class="com.bighorn.config.PostProcessor"/>

    public static void main(String[] args) {
        //获取 ClassPathXmlApplicationContext 容器
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        //从容器中获取对象
        User user = context.getBean("user", User.class);
        //使用bean
        System.out.println("使用bean："+user);
        //调用close方法关闭容器
        context.close();
    }