[Java知识库]Spring学习（4）—— IOC容器-Bean管理（xml方式）bean的作用域与生命周期

一.??bean的作用域

1. Spring默认是单实例对象

package pojo;

public class User {
    private String userName;

    private String password;

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

<?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">

    <!-- 创建对象 -->
    <bean id="user" class="pojo.User"></bean>
</beans>

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import pojo.User;

public class testSpring {
    @Test
    public void testUser() {
        //加载配置文件
        ApplicationContext context = new ClassPathXmlApplicationContext("User.xml");

        //获取配置文件创建的对象
        User user1 = context.getBean("user", User.class);

        User user2 = context.getBean("user",User.class);

        System.out.println(user1);  //pojo.User@3ce1e309   地址相同
        System.out.println(user2);  //pojo.User@3ce1e309
    }
}

2. 设置单实例还是多实例

<?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">

    <!-- 创建对象 -->
    <!-- scope默认是singleton（单实例） 可以设置为prototype（多实例）-->
    <bean id="user" class="pojo.User" scope="prototype"></bean>
</beans>

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import pojo.User;

public class testSpring {
    @Test
    public void testUser() {
        //加载配置文件
        ApplicationContext context = new ClassPathXmlApplicationContext("User.xml");

        //获取配置文件创建的对象
        User user1 = context.getBean("user", User.class);

        User user2 = context.getBean("user",User.class);

        System.out.println(user1);  //pojo.User@15ff3e9e  地址不同
        System.out.println(user2);  //pojo.User@5fdcaa40
    }
}

二.??bean的生命周期

1.执行无参构造器创建bean实例；2.调用set方法，设置属性的值；3.执行初始化方法；4.获取创建的bean对象；5.执行销毁的方法?

package pojo;

public class User {
    private String userName;

    public User() {
        System.out.println("1.执行无参构造器创建bean实例");
    }

    public void setUserName(String userName) {
        this.userName = userName;
        System.out.println("2.调用set方法，设置属性的值");
    }

    //创建执行的初始化方法
    public void initMethod(){
        System.out.println("3.执行初始化方法");
    }

    //创建执行的销毁的方法
    public void destroyMethod(){
        System.out.println("5.执行销毁的方法");
    }

}

<?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">

    <!-- 创建对象 -->
    <bean id="user" class="pojo.User" init-method="initMethod" destroy-method="destroyMethod">
        <property name="userName" value="Tom"></property>
    </bean>
</beans>

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import pojo.User;

public class testSpring {
    @Test
    public void testUser() {
        //加载配置文件
        ApplicationContext context = new ClassPathXmlApplicationContext("User.xml");

        //获取配置文件创建的对象
        User user = context.getBean("user", User.class);
        System.out.println("4.获取创建的bean对象");

        //销毁bean实例
        ((ClassPathXmlApplicationContext) context).close();
    }
}
//        1.执行无参构造器创建bean实例
//        2.调用set方法，设置属性的值
//        3.执行初始化方法
//        4.获取创建的bean对象
//        5.执行销毁的方法

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