bean的生命周期

目录

1.单例bean

2.多例bean

1.单例bean

• 案例

<bean id="userService" class="com.by.service.UserServiceImpl"
      			scope="singleton" init-method="init" destroy-method="destroy">

/**
 * 业务层实现类
 */
public class UserServiceImpl implements UserService {

    private UserDao userDao;

    public UserServiceImpl() {
        System.out.println("调用构造方法创建bean...");
    }

    public void setUserDao(UserDao userDao) {
        System.out.println("调用set方法注入值...");
        this.userDao = userDao;
    }

    public void init(){
        System.out.println("调用init方法初始化bean...");
    }

    public void destroy(){
        System.out.println("调用destroy方法销毁bean...");
    }

    public void addUser(){
        userDao.addUser();
    }
}

/**
 * 模拟表现层
 */
public class Client {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext ac = 
        	new ClassPathXmlApplicationContext("applicationContext.xml");
        //关闭容器
        ac.close();
    }
}

生命周期：

[容器启动]--->构造方法(实例化)--->set方法(注入)--->init方法(初始化)--->[容器关闭]--->destroy方法(销毁)

2.多例bean

• 案例

<bean id="userService" class="com.by.service.UserServiceImpl"
      			scope="prototype" init-method="init" destroy-method="destroy">

/**
 * 业务层实现类
 */
public class UserServiceImpl implements UserService {

    private UserDao userDao;

    public UserServiceImpl() {
        System.out.println("调用构造方法创建bean...");
    }

    public void setUserDao(UserDao userDao) {
        System.out.println("调用set方法注入值...");
        this.userDao = userDao;
    }

    public void init(){
        System.out.println("调用init方法初始化bean...");
    }

    public void destroy(){
        System.out.println("调用destroy方法销毁bean...");
    }

    public void addUser(){
        userDao.addUser();
    }
}

/**
 * 模拟表现层
 */
public class Client {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext ac = 
            	new ClassPathXmlApplicationContext("applicationContext.xml");
        //使用对象
        ac.getBean("userService");
    }
}

生命周期：

[使用对象]---->构造方法(实例化)--->set方法(注入)--->init方法(初始化)--->[JVM垃圾回收]--->destroy方法(销毁)