Spring Bean作用域简介

最新推荐文章于 2020-09-02 10:46:28 发布

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本文详细解析了Spring框架中Bean的五种作用域：singleton、prototype、request、session及application，探讨了每种作用域下Bean实例的生命周期及应用场景，特别强调了在web环境下各作用域的适用场景。

按照spring官网说明，分成如下五种

Scope	Description
singleton	(Default) Scopes a single bean definition to a single object instance for each Spring IoC container.
prototype	Scopes a single bean definition to any number of object instances.
request	Scopes a single bean definition to the lifecycle of a single HTTP request. That is, each HTTP request has its own instance of a bean created off the back of a single bean definition. Only valid in the context of a web-aware Spring `ApplicationContext`.
session	Scopes a single bean definition to the lifecycle of an HTTP `Session`. Only valid in the context of a web-aware Spring `ApplicationContext`.
application	Scopes a single bean definition to the lifecycle of a `ServletContext`. Only valid in the context of a web-aware Spring `ApplicationContext`.
websocket	Scopes a single bean definition to the lifecycle of a `WebSocket`. Only valid in the context of a web-aware Spring `ApplicationContext`.

singleton 单例模式 spring默认容器里面的一个对象的实例只有一个

举个栗子：

public class Person {
    public String getName() {
        return name;
    }

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

    private String name;

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

XML:

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">

<bean id="person" class="demo.guhong.test04.Person" scope="singleton" name="person2">
    <property name="name" value="bitch"/>
</bean>
</beans>

测试:

public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("testbeans.xml");

        Person person = (Person) context.getBean("person");

        Person person2 = (Person) context.getBean("person2");

        System.out.println(person == person2);

    }

----------------------------------------------------

true

Process finished with exit code 0

prototype 原型模式：每次从容器中取出来的时候，都是新对象

还是上面的Person,修改xml 中bean属性:scope

<bean id="person" class="demo.guhong.test04.Person" scope="prototype" name="person2">
    <property name="name" value="bitch"/>
</bean>

结果：

----------------------------------------------------

false

Process finished with exit code 0

request sessoion application websocket

都是在web中用到各自对应不同情形的bean存活时间段，后续有机会待补充