spring的注解(1): @Configuration,@Bean,@Component,

最新推荐文章于 2025-03-13 18:46:26 发布

saioAc

最新推荐文章于 2025-03-13 18:46:26 发布

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文章标签： spring

本文详细解释了Spring框架中@Configuration和@Bean注解的使用方法及区别。介绍了@Bean如何定义bean实例，以及@Configuration如何组织这些bean定义。同时对比了@Bean在不同上下文中的行为表现。

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@Configuration和@Bean

@Configuration 相当于<beans> 可以用在类,接口(包括注解类型),或者枚举声明上
@Bean 相当于<bean>,这个只能用在方法或者注解类型声明上
所以

@Configuration
public class AppConfig {
    @Bean
    public MyService myService() {
        return new MyServiceImpl();
    }
}

就相当于

<beans>
    <bean id="myService" class="com.acme.services.MyServiceImpl"/>
</beans>

@Configuration和@Component的区别

在spring-framework的文档里写了

Full @Configuration vs 'lite' @Beans mode?
When @Bean methods are declared within classes that are not annotated with @Configuration
they are referred to as being processed in a 'lite' mode. For example, bean methods declared in
a @Component or even in a plain old class will be considered 'lite'.
Unlike full @Configuration, lite @Bean methods cannot easily declare inter-bean dependencies.
Usually one @Bean method should not invoke another @Bean method when operating in 'lite' mode.
Only using @Bean methods within @Configuration classes is a recommended approach of
ensuring that 'full' mode is always used. This will prevent the same @Bean method from accidentally
being invoked multiple times and helps to reduce subtle bugs that can be hard to track down when
operating in 'lite' mode.