spring(二)：bean的生命周期

bean的生命周期指的是bean的创建——>初始化——>销毁的过程，该过程是由spring容器进行管理的

我们可以自定义bean初始化和销毁的方法：容器在bean进行到当前生命周期时，调用自定义的初始化和销毁方法

自定义初始化和销毁方法

init-method、destroy-method

配置文件的bean标签中配置init-method、destroy-method属性

<bean id="user" class="com.enjoy.study.pojo.User" init-method="init" destroy-method="destroy"/>

---

bean类
public class User {
    public User() {
        System.out.println("user....constructor..........");
    }

    public void init(){
        System.out.println("user....init..........");
    }

    public void destroy(){
        System.out.println("user....destroy..........");
    }
}

---

测试类
public class Cap7Test {
    @Test
    public void cap7Test(){
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:beans.xml");
        System.out.println("ioc容器启动完成");
        context.close();
    }
}

---

结果
user....constructor..........
user....init..........

ioc容器启动完成
user....destroy..........

initMethod、destroyMethod

@Bean配置initMethod、destroyMethod属性

单实例情况：

@Configuration
public class Cap7MainConfig {
    @Bean(initMethod = "init",destroyMethod = "destroy")
    public User user(){
        return new User();
    }
}

---

测试方法
@Test
public void annoTest(){
	AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(Cap7MainConfig.class);
	System.out.println("ioc容器启动完成");
	context.close();
}

---

结果
user....constructor..........
user....init..........

ioc容器启动完成
user....destroy..........

多实例情况：

@Configuration
public class Cap7MainConfig {
    @Scope("prototype")
    @Bean(initMethod = "init",destroyMethod = "destroy")
    public User user(){
        return new User();
    }
}

---

结果
ioc容器启动完成　　

单实例情况下，容器启动时完成bean的实例化，容器关闭时进行bean的销毁

多实例情况下，容器启动时不进行bean的实例化，获取bean时实例化bean对象，所以启动后直接关闭容器，容器中并未进行bean的管理

InitializingBean、DisposableBean接口

bean实现InitializingBean接口，实现afterPropertiesSet()方法：beanFactory创建对象完成，并且设置完属性后，调用该方法，相当于初始化方法

bean实现DisposableBean接口，实现destroy()方法：bean对象销毁时，调用该方法

public class User implements InitializingBean,DisposableBean {
    public User() {
        System.out.println("user....constructor..........");
    }

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

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

---

配置类
@Configuration
public class Cap7MainConfig {
    @Bean
    public User user(){
        return new User();
    }
}

---

结果
user....constructor..........
user....afterPropertiesSet.........
ioc容器启动完成
user....destroy............

@PostConstruct、@PreDestroy

@Component
public class User{
    public User() {
        System.out.println("user....constructor..........");
    }

    //对象创建并赋值后使用
    @PostConstruct
    public void init() {
        System.out.println("user....init.........");
    }

    //容器移除对象之前回调通知，销毁bean
    @PreDestroy
    public void destroy() {
        System.out.println("user....destroy............");
    }
}

---

配置类
@Configuration
@ComponentScan("com.enjoy.study.cap7")
public class Cap7MainConfig {
}

---

结果
user....constructor..........
user....init.........

ioc容器启动完成
user....destroy............

BeanPostProcessor

后置处理器，负责在初始化前后做相应处理

/**
 * 后置处理器
 * @Component，将后置处理器加入容器中
 * @author qf
 * @create 2019-05-22 10:05
 */
@Component
public class MyBeanPostProcessor implements BeanPostProcessor {

    /**
     * 在初始化之前进行相应后置处理工作。比如在init-method方法执行之前，或者initializingBean的afterPropertiesSet方法之前
     * @param bean
     * @param beanName
     * @return
     * @throws BeansException
     */
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessBeforeInitialization......"+bean+"........."+beanName);
        return bean;
    }

    /**
     * 在初始化之后进行相应后置处理工作
     * @param bean
     * @param beanName
     * @return
     * @throws BeansException
     */
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessAfterInitialization......"+bean+"........."+beanName);
        return bean;
    }
}

测试

@Component
public class User implements InitializingBean,DisposableBean {

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

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

---

配置类
@Configuration
@ComponentScan("com.enjoy.study.cap8")
public class Cap8MainConfig {
}

---

测试类
public class Cap8Test {
    @Test
    public void cap8Test(){
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(Cap8MainConfig.class);
        System.out.println("ioc容器创建完成");
        context.close();
    }
}

---

结果
postProcessBeforeInitialization...............org.springframework.context.event.internalEventListenerProcessor
postProcessAfterInitialization...............org.springframework.context.event.internalEventListenerProcessor
postProcessBeforeInitialization...............org.springframework.context.event.internalEventListenerFactory
postProcessAfterInitialization...............org.springframework.context.event.internalEventListenerFactory
postProcessBeforeInitialization...............cap8MainConfig
postProcessAfterInitialization...............cap8MainConfig
postProcessBeforeInitialization...............user
user....afterPropertiesSet........
postProcessAfterInitialization...............user

ioc容器创建完成

user....destroy........