Spring Bean的生命周期

Springbean的生命周期为bean对象从创建到销毁的过程，他有两种情况

一，不添加后置处理器的情况

1，构造器方法
2，set方法
3，初始化方法
4，实例化bean
5，销毁方法

代码示例
Student类

package awz;

/**
 * bean的生命周期
 * @version 1.0
 * @Author:杨杰
 * @Date:2022/4/6 8:53
 */
public class Student {


    private String name;

    public Student() {
        System.out.println("1 调用无参构造");
    }



    public String getName() {
        return name;
    }

    public void setName(String name) {
        System.out.println("2，调用set方法");
        this.name = name;
    }

    public void initMethod() {
        System.out.println("3，初始化方法");
    }

    public void destroyMethod() {
        System.out.println("5,销毁方法");
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                '}';
    }
}

xml配置

<?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 id="student" class="awz.Student" init-method="initMethod" destroy-method="destroyMethod">
        <property name="name" value="yj"></property>
    </bean>

</beans>

运行测试

public class Mytest {

    @Test
    public void testHello() {

        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beanStudent.xml");

        Student student = context.getBean("student", Student.class);
        System.out.println("4,实例化student");
        context.close();


    }

}

二添加后置处理器的方法

1，构造器方法
2，set方法
在初始化之前执行
3，初始化方法
在初始化之后执行
4，实例化bean
5，销毁方法

需要注意的是第4步和第6步：把 bean 实例传递 bean 后置处理器的方法
需要传递bean示例

创建Students类实现BeanPostProcessor

package awz;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

/**
 * @version 1.0
 * @Author:杨杰
 * @Date:2022/4/6 9:03
 */
public class Students implements BeanPostProcessor {

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("初始化方法之前调用");
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("初始化方法之后调用");
        return bean;
    }

}

xml配置

<?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 id="student" class="awz.Student" init-method="initMethod" destroy-method="destroyMethod">
        <property name="name" value="yj"></property>
    </bean>

    <bean id="students" class="awz.Students">
    </bean>

</beans>

测试

import awz.Hello;
import awz.Student;
import awz.Students;
import awz.User;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @version 1.0
 * @Author:杨杰
 * @Date:2022/4/3 21:59
 */
public class Mytest {

    @Test
    public void testHello() {

        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beanStudent.xml");

        Students students = context.getBean("students", Students.class);
        System.out.println("5,实例化students");
        context.close();


    }

}