Spring中@Conditional注解的用法

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Conditional {
    Class<? extends Condition>[] value();
}

@FunctionalInterface
public interface Condition {
    boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata);
}

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Dog {
    private String name;
    private String gender;
}

public class MyCondition implements Condition {
    /**
     * 重写matches方法， 返回true则注入bean，false则不注入。
     * */
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
        // 如果容器中注入了 dog 就返回true
        if(beanFactory.containsBean("dog")){
            return true;
        }
        return false;
    }
}

@Configuration
public class MyConfig {

    @Bean("dog")
    //@ConditionalOnBean(name = {"dog2"})
    public Dog dog1(){
        return new Dog("金毛","公");
    }

    @Bean("dog1")
    @Conditional(value = MyCondition.class)
    public Dog dog2(){
        return new Dog("拉布拉多","母");
    }
}

public class tets {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MyConfig.class);
         Map<String, Dog> beansOfType = applicationContext.getBeansOfType(Dog.class);
        System.out.println(beansOfType);
    }
}

public class MyCondition implements Condition {
    /**
     * 重写matches方法， 返回true则注入bean，false则不注入。
     * */
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
        // 如果容器中之前注入了 dog 就返回false
        if(beanFactory.containsBean("dog")){
            return false;
        }
        return true;
    }
}

@Configuration
public class MyConfig {

    @Bean("dog")

    public Dog dog1(){
        return new Dog("金毛","公");
    }

    @Bean("dog1")
    @ConditionalOnBean(name = {"dog"})// spring容器中有dog这个Bean 才会创建dog1
//    @ConditionalOnMissingBean(name = {"dog"})// spring容器中不存在 dog这个Bean 才会创建dog1
    public Dog dog2(){
        return new Dog("拉布拉多","母");
    }
}