Spring @Conditional注解demo

@Conditional作用是按照一定的条件进行判断，满足条件就给容器注册bean，它可以用在带有@Bean注解的方法上，如果给定条件计算结果为true，就会创建bean，否则就会忽略这个bean。

package com.lian.demo.bean;

import lombok.Data;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypemetadata;

@Data
public class Person implements Condition {

    @Override
    public boolean matches(ConditionContext context, AnnotatedTypemetadata metadata) {
    	//返回true，则注入bean，否则忽略bean
        return true;
    }
}

package com.lian.demo.service;

import com.lian.demo.bean.Person;
import com.lian.demo.bean.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Conditional;
import org.springframework.stereotype.Component;

@Component
public class AutoConfig {

	//如果条件为true则创建bean，否则忽略bean
    @Conditional(value = Person.class)
    //bean别名pi
    @Bean(name = "pi")  
    public User user(){
        return new User("dan",3);
    }
}

@RunWith(SpringRunner.class)
@SpringBootTest
public class ConditionDemo {

    @Autowired
    ApplicationContext applicationContext;

    @Test
    public void run(){
        User user = (User) applicationContext.getBean("pi");
        System.out.println("用户姓名"+user.getName()+"年龄"+user.getAge());
    }
}

如果注入bean成功，返回结果

用户姓名dan年龄3

如果注入bean失败，返回结果

org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'pi' available