Spring中@DependsOn注解的使用代码实例

/**
 * Beans on which the current bean depends. Any beans specified are guaranteed to be
 * created by the container before this bean. Used infrequently in cases where a bean
 * does not explicitly depend on another through properties or constructor arguments,
 * but rather depends on the side effects of another bean's initialization.
 *
 * <p>A depends-on declaration can specify both an initialization-time dependency and,
 * in the case of singleton beans only, a corresponding destruction-time dependency.
 * Dependent beans that define a depends-on relationship with a given bean are destroyed
 * first, prior to the given bean itself being destroyed. Thus, a depends-on declaration
 * can also control shutdown order.
 *
 * <p>May be used on any class directly or indirectly annotated with
 * {@link org.springframework.stereotype.Component} or on methods annotated
 * with {@link Bean}.
 *
 * <p>Using {@link DependsOn} at the class level has no effect unless component-scanning
 * is being used. If a {@link DependsOn}-annotated class is declared via XML,
 * {@link DependsOn} annotation metadata is ignored, and
 * {@code <bean depends-on="..."/>} is respected instead.
 *
 * @author Juergen Hoeller
 * @since 3.0
 */
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DependsOn {
	String[] value() default {};
}

@Component
public class ASource {
    public ASource(){
        System.out.println("事件创建");
    }
}

@Component
public class BListener {
    public BListener(){
        System.out.println("监听创建");
    }
}

// 事件创建
// 监听创建

@Component
@DependsOn(value = {"BListener"})
public class ASource {
    public ASource(){
        System.out.println("事件创建");
    }
}

// 监听创建
// 事件创建

@Configuration
public class Config {
    @Bean
    @DependsOn(value = {"BListener"})
    public ASource aSource(){
        return new ASource();
    }
    @Bean
    public BListener bListener(){
        return new BListener();
    }
}

// 监听创建
// 事件创建