在spring里面，默认情况下，bean是一个单实例对象

package com.test2;

public class TestA {
    private String name;

    public void setName(String name) {
        this.name = name;
    }
}

<?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="testA" class="com.test2.TestA">
        <property name="name" value="名字"/>
    </bean>
</beans>

package com.test2;


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

public class TestATest {
    @Test
    public void test(){
        ApplicationContext context = new ClassPathXmlApplicationContext("spring7.xml");
        TestA testA = context.getBean("testA", TestA.class);
        System.out.println(testA);
        TestA testb = context.getBean("testA", TestA.class);
        System.out.println(testb);
    }
}

在spring里面，设置创建bean实例是单例还是多例

在spring配置文件bean标签里面有属性(scope)用于设置单实例还是多实例

scope属性常用值

singleton，默认值，单例的

prototype，多例的

补充两个不是很常用的值

request 一次请求

session 一次会话

<?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="testA" class="com.test2.TestA" scope="prototype">
        <property name="name" value="名字"/>
    </bean>
</beans>

package com.test2;


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

public class TestATest {
    @Test
    public void test(){
        ApplicationContext context = new ClassPathXmlApplicationContext("spring7.xml");
        TestA testA = context.getBean("testA", TestA.class);
        System.out.println(testA);
        TestA testb = context.getBean("testA", TestA.class);
        System.out.println(testb);
    }
}

singleton和prototype的区别

singleton单实例，prototype多实例

设置scope值为singleton时，加载spring配置文件的时候就会创建单例对象

设置scope的值为prototype时，它并不是在加载spring配置文件的时候创建对象，而是在调用getBean方法的时候创建多例对象