基于Xml方式的Bean的配置-Bean的作用范围scope配置

news2024/11/20 3:37:37

SpringBean的配置详解

Bean的配置范围
- 默认情况下（基本的Spring环境），单纯Spring环境Bean的作用范围有两个：Singleton和prototype
- singleton:单例，默认值，Spring容器创建的时候，就会进行Bean的实例化，并储存到Bean的内部的单例池中，每次getBean时都是从单例池中获取相同的Bean实例
- prototype：原型，Spring容器初始化时不会创建Bena实例，当调用getBean时才会实例化Bean，每次getBean都会创建一个新的Bean实例。

当scope=singleton时

    <bean id="userService" class="com.example.Service.Impl.UserServiceImpl" scope="singleton">

        ApplicationContext context = new ClassPathXmlApplicationContext("application.xml");
        Object userService1 = context.getBean("userService");
        Object userService2 = context.getBean("userService");
        Object userService3 = context.getBean("userService");
        System.out.println(userService1);
        System.out.println(userService2);
        System.out.println(userService3);

运行结果如下：

当scope=prototype时

    <bean id="userService" name="aaa,bbb" class="com.example.Service.Impl.UserServiceImpl" scope="prototype">

        ApplicationContext context = new ClassPathXmlApplicationContext("application.xml");
        Object userService1 = context.getBean("userService");
        Object userService2 = context.getBean("userService");
        Object userService3 = context.getBean("userService");
        System.out.println(userService1);
        System.out.println(userService2);
        System.out.println(userService3);

运行结果

PS：如果添加了SpringWebMVC依赖，scope的值就有多个

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.3.7</version>
        </dependency>