生命周期 - 码农教程

1、初始化和销毁

在目标方法执行前后进行初始化或销毁

（1）在Service方法的实现类里面创建初始化方法和销毁方法：

public class StudentServiceImpl implements StudentService {
    private StudentDao studentDao;

    public StudentServiceImpl() {
        System.out.println("service的实现类被创建了！！");
    }

    public StudentDao getStudentDao() {
        return studentDao;
    }
    public void setStudentDao(StudentDao studentDao) {
        this.studentDao = studentDao;
    }
    public void addStudent(){
        System.out.println("StudentService的实现类的Add方法！！");
        studentDao.addStudent();
    }
    public void myInit(){
        System.out.println("初始化方法");
    }
    public void myDestory(){
        System.out.println("销毁方法");
    }
}

（2）配置文件中对初始化方法和销毁方法进行配置：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" 
xsi:schemaLocation="http://www.springframework.org/schema/beans 
http://www.springframework.org/schema/beans/spring-beans-4.2.xsd ">
    <bean id="studentDao" class="pers.zhb.dao.StudentDaoImpl">
    </bean>

    <bean id="studentService" class="pers.zhb.service.StudentServiceImpl"
          init-method="myInit" destroy-method="myDestory">
        <property name="studentDao" ref="studentDao"></property>
    </bean>
</beans>

（3）测试：

public class TestCycle {
    public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        ApplicationContext applicationContext=new
                ClassPathXmlApplicationContext("applicationContext.xml");//创建容器对象
        StudentService studentService= (StudentService) applicationContext.getBean("studentService");
        studentService.addStudent();
        applicationContext.getClass().getMethod("close").invoke(applicationContext);
    }
}

必须执行close方法（这里是利用反射调用的close()方法）后销毁方法才会执行，必须是单例的。

（4）作用：

初始化方法：用于准备数据等

销毁方法：释放资源等

2、BeanPostProcessor后处理Bean

spring提供一种机制，只要实现了BeanPostProcessor接口，并将实现类提供给spring容器，spring容器将会自动执行，在初始化方法前执行before()，初始化方法后执行after()

spring提供工厂勾子，用于修改实例对象，可以生成代理对象，是AOP的底层

（1）创建MyBeanPostProcessor类，实现 BeanPostProcessor 接口：

public class MyBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object o, String s) throws BeansException {
        System.out.println("前方法"+s);
        return o;
    }

    @Override
    public Object postProcessAfterInitialization(Object o, String s) throws BeansException {
        System.out.println("后方法"+s);
        return o;
    }
}

（2）配置文件：

<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xmlns="http://www.springframework.org/schema/beans" 
xsi:schemaLocation="http://www.springframework.org/schema/beans 
http://www.springframework.org/schema/beans/spring-beans-4.2.xsd ">
    <bean id="studentDao" class="pers.zhb.dao.StudentDaoImpl">
    </bean>

    <bean id="studentService" class="pers.zhb.service.StudentServiceImpl"
          init-method="myInit" destroy-method="myDestory">
        <property name="studentDao" ref="studentDao"></property>
    </bean>
    <bean class="pers.zhb.abc.MyBeanPostProcessor"></bean>
</beans>

（3）测试：

public class TestCycle {
    public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        ApplicationContext applicationContext=new
                ClassPathXmlApplicationContext("applicationContext.xml");//创建容器对象
        StudentService studentService= (StudentService) applicationContext.getBean("studentService");
        studentService.addStudent();
        applicationContext.getClass().getMethod("close").invoke(applicationContext);
    }
}

前方法studentDao
后方法studentDao
service的实现类被创建了！！
前方法studentService
初始化方法
后方法studentService
StudentService的实现类的Add方法！！
StudentDao的实现类的Add方法！！
四月 13, 2020 3:54:12 下午 org.springframework.context.support.AbstractApplicationContext doClose
信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@3f91beef: startup date [Mon Apr 13 15:54:11 CST 2020]; root of context hierarchy
销毁方法

（4）动态代理的方式：

public class MyBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object o, String s) throws BeansException {
        System.out.println("前方法"+s);
        return o;
    }

    @Override
    public Object postProcessAfterInitialization(Object o, String s) throws BeansException {
        System.out.println("后方法"+s);
        return Proxy.newProxyInstance(MyBeanPostProcessor.class.getClassLoader(), o.getClass().getInterfaces(), new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                System.out.println("开启事务");
                //执行目标方法
                Object o1=method.invoke(o,args);
                System.out.println("提交事务");
                return o1;

            }
        });
    }
}

前方法studentDao
后方法studentDao
service的实现类被创建了！！
前方法studentService
初始化方法
后方法studentService
开启事务
StudentService的实现类的Add方法！！
开启事务
StudentDao的实现类的Add方法！！
提交事务
提交事务
四月 13, 2020 4:09:20 下午 org.springframework.context.support.AbstractApplicationContext doClose
信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@3f91beef: startup date 
[Mon Apr 13 16:09:20 CST 2020]; root of context hierarchy
销毁方法

原文地址：https://www.cnblogs.com/zhai1997/p/12692026.html