bean-callback

前言

测试下，spring bean 生命周期的几种回调函数，初始化方法，销毁方法

一、环境

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-beans</artifactId>
        <version>4.3.26.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.3.26.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.3.26.RELEASE</version>
    </dependency>
</dependencies>

二、代码测试

1、xml 配置 init destory

通过在xml配置bean的 init-method、destroy-method

public class Person {
    private String name;
    private String age;
 	// getter setter
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }
    
    public void init() {
        System.out.println("person init ~");
    }
    
    public void destroy() {
        System.out.println("person  destory ~");
    }
    
}

<bean class="com.juststand.bean.model.Person" id="person" init-method="init" destroy-method="destroy">
    <property name="age" value="10" ></property>
    <property name="name" value="test" ></property>
</bean>

public class Test {
    
    public static void main(String[] args) throws InterruptedException {
    
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("model.xml");
        Person person = applicationContext.getBean("person", Person.class);
        System.out.println(person);
        Thread.sleep(2000);
        applicationContext.destroy();
        System.out.println("context destory");
    }
}

结果

person init ~
Person{name=’test’, age=’10’}
person destory ~
context destory

2、注解

通过@PostConstruct、@PreDestroy

public class Student {
    private String name;
    private int level;
    // getter setter
    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", level=" + level +
                '}';
    }
    
    @PostConstruct
    public void init() {
        System.out.println("student iniit");
    }
    
    @PreDestroy
    public void destory() {
        System.out.println("student destory");
    }
}

// 注解配置需要开启才行
<context:annotation-config></context:annotation-config>
<bean class="com.juststand.bean.model.Student" id="student">
    <property name="level" value="1" ></property>
    <property name="name" value="test" ></property>
</bean>

public static void main(String[] args) throws InterruptedException {
    
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("model.xml");    
        Student student = applicationContext.getBean("student", Student.class);
        System.out.println(student.toString());
        Thread.sleep(2000);
        applicationContext.destroy();
        System.out.println("context destory");
    }

结果

student init
Student{name=’test’, level=1}
student destory
context destory

3、实现接口

bean 实行 InitializingBean 、DisposableBean 这两个接口

public class Zoo implements InitializingBean, DisposableBean {
    private String name;
   	// getter setter
    @Override
    public String toString() {
        return "Zoo{" +
                "name='" + name + '\'' +
                '}';
    }
    
    public void destroy() throws Exception {
        System.out.println("zoo destory");
    }
    
    public void afterPropertiesSet() throws Exception {
        System.out.println("zoo initing");
    }
}

<bean class="com.juststand.bean.model.Zoo" id="zoo">
    <property name="name" value="zoo"></property>
</bean>

public class Test {
    public static void main(String[] args) throws InterruptedException {
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("model.xml");
        Zoo zoo = applicationContext.getBean("zoo", Zoo.class);
        System.out.println(zoo.toString());
        Thread.sleep(2000);
        applicationContext.destroy();
        System.out.println("context destory");
    }
}

结果

zoo initing
Zoo{name=’zoo’}
zoo destory
context destory

三、注意事项

• 初始化回调方法是在 属性赋值 set 方法之后调用
• 如果三种都使用了且方法不同，执行顺序如下
  • @PostConstruct > InitializingBean.afterPropertiesSet() > init-method
  • @PreDestroy > DisposableBean.destroy() > destroy-init

// zoo初始化为例
// DefaultSingletonBeanRegistry.getSingleton() -> AbstractAutowireCapableBeanFactory.doCreateBean()进行实例化
try {
   // 实例化完成
   // 属性赋值
   populateBean(beanName, mbd, instanceWrapper);
   if (exposedObject != null) {
      // 初始化 回调方法
      exposedObject = initializeBean(beanName, exposedObject, mbd);
   }
}

protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
      throws Throwable {

   boolean isInitializingBean = (bean instanceof InitializingBean);
   if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
      if (logger.isDebugEnabled()) {
         logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
      }
      if (System.getSecurityManager() != null) {
         try {
            AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
               @Override
               public Object run() throws Exception {
                  ((InitializingBean) bean).afterPropertiesSet();
                  return null;
               }
            }, getAccessControlContext());
         }
         catch (PrivilegedActionException pae) {
            throw pae.getException();
         }
      }
      else {
          // 具体初始化方法
         ((InitializingBean) bean).afterPropertiesSet();
      }
   }
}