Spring中@Conditional注解的说明

@Conditional

它的作用是按照一定的条件进行判断，满足注解中的条件就给容器注册bean。其他则不注入。这个注解既可以写在方法上也可以写在类上。这个注解被大量的使用在spring Boot中。

实现condition

1. 首先定义一个配置类

@Configuration
//定义在类上
@Conditional(WindowCondition.class)
public class MyConfig2 {
    @Bean("window")
    //定义在方法上
    @Conditional(WindowCondition.class)
    public Person person01(){
        return new Person("王五",50);
    }
    @Bean("linux")
     //定义在方法上
    @Conditional(LinuxCondition.class)
    public Person person02(){
        return new Person("linux",48);
    }
}

2. 写两个条件也就是condition类，这个类要实现condition接口，并且要重写matches方法

public class LinuxCondition implements Condition {
    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        Environment environment = conditionContext.getEnvironment();
        String property = environment.getProperty("os.name");
        if (property.toLowerCase().contains("linux")){
            return true;
        }
        return false;
    }
}

public class WindowCondition implements Condition {
    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        Environment environment = conditionContext.getEnvironment();
        String property = environment.getProperty("os.name");
        if (property.toLowerCase().contains("window")){
            return true;
        }
        return false;
    }
}

3. 测试类

public class App {
    public static void main(String[] args) {

        //读取注解
        ApplicationContext applicationContext1 = new AnnotationConfigApplicationContext(MyConfig.class);
        //打印出IOC容器中已经加载的组件
        String[] names=  applicationContext1.getBeanNamesForType(Person.class);
        for (String name:names){
           System.out.println(name);
        }
    }
}