@Conditional

• 按照条件创建对象放入容器

1. 测试代码

@ComponentScan("com.alex.person")
@Configuration
public class ConditionalConfig {
    @Conditional({MacOSCondition.class})//如果这个类条件通过就加载
    @Bean
    public Person person() {
        return new Person(1, "alex");
    }
}

public class MacOSCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        Environment env = context.getEnvironment();
        // bean定义的注册类
        context.getRegistry();
        metadata.getAnnotations();
        String properties = env.getProperty("os.name");
        if (properties.contains("Mac OS X")) { // 如果是mac系统就加载
            System.out.println("允许注入 系统: " + properties);
            return true;
        }
        return false;
    }
}

结果

允许注入 系统: Mac OS X
org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
org.springframework.context.event.internalEventListenerProcessor
org.springframework.context.event.internalEventListenerFactory
conditionalConfig
person
personServiceImpl

• 小结 @Conditional(xxx.class) 根据这个实现Condition接口的类来判断是否将这个bean放入容器,如果不满足会报错! 这是最简单的使用.