解决Circular reference问题

错误代码：

package com.imooc.miaosha.redis;

import com.alibaba.fastjson.JSON;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Service;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;

@Service
public class RedisService {

    @Autowired
    JedisPool jedisPool;
    @Autowired
    RedisConfig redisConfig;

    public  T get(String key,Class clazz){

        Jedis jedis = null;     //连接池用完后一定要释放掉，不然导致连接不够用
        try{
            jedis=jedisPool.getResource();
            String str=jedis.get(key);
            T t=stringToBean(str,clazz);
            return t;
        }finally {
            returnToPool(jedis);
        }
    }

    public  boolean set(String key,T value){

        Jedis jedis = null;
        try{
            jedis=jedisPool.getResource();
            String str= beanToString(value);
            if(str==null||str.length()<=0){
                return  false;
            }
            jedis.set(key,str);
            return true;
        }finally {
            returnToPool(jedis);
        }
    }

    private  String beanToString(T value) {
        if (value == null) {         //加入value是int类型，无法通过json转化字符串，所以要判断
             return null;
        }
        Class clazz = value.getClass();
        if(clazz==int.class||clazz==Integer.class){     //先处理这几种，其它情况可日后根据情况再完善
           return ""+value;
        }else if(clazz==String.class){
           return (String)value;
        }else if(clazz==long.class||clazz==Long.class){
           return ""+value;
        }else{
            return JSON.toJSONString(value);
        }

    }

    private  T stringToBean(String str,Class clazz) {   //参数校验是必不可少的
        if(str==null||str.length()<=0||clazz==null)
            return null;
        if(clazz==int.class||clazz==Integer.class){
            return (T)Integer.valueOf(str);
        }else if(clazz==String.class){
            return (T)str;
        }else if(clazz==long.class||clazz==Long.class){
            return (T)Long.valueOf(str);
        }else{
            return JSON.toJavaObject(JSON.parseObject(str),clazz);
        }
    }

    private void returnToPool(Jedis jedis){
        if(jedis!=null){
            jedis.close();//返回连接池，并不会关闭，看源码可以知道
        }
    }

    @Bean
    public JedisPool jedisPoolFactory(){     //@bean注解将bean注入到容器中
        JedisPoolConfig poolConfig = new JedisPoolConfig();
        poolConfig.setMaxIdle(redisConfig.getPoolMaxldle());
        poolConfig.setMaxTotal(redisConfig.getPoolMaxTotal());
        poolConfig.setMaxWaitMillis(redisConfig.getPoolMaxWait()*1000);
        JedisPool jp=new JedisPool(poolConfig,redisConfig.getHost(),redisConfig.getPort(),redisConfig.getTimeout()*1000,redisConfig.getPassword(),0);
        return jp;
    }
}

报错信息：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'sampleController': Unsatisfied dependency expressed through field 'redisService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'redisService': Unsatisfied dependency expressed through field 'jedisPool'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jedisPoolFactory' defined in class path resource [com/imooc/miaosha/redis/RedisService.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [redis.clients.jedis.JedisPool]: Circular reference involving containing bean 'redisService' - consider declaring the factory method as static for independence from its containing instance. Factory method 'jedisPoolFactory' threw exception; nested exception is java.lang.NullPointerException
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1264) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) ~[spring-context-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.9.RELEASE.jar:1.5.9.RELEASE]
	at com.imooc.miaosha.MainApplication.main(MainApplication.java:9) [classes/:na]
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'redisService': Unsatisfied dependency expressed through field 'jedisPool'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jedisPoolFactory' defined in class path resource [com/imooc/miaosha/redis/RedisService.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [redis.clients.jedis.JedisPool]: Circular reference involving containing bean 'redisService' - consider declaring the factory method as static for independence from its containing instance. Factory method 'jedisPoolFactory' threw exception; nested exception is java.lang.NullPointerException
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1264) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:208) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1138) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	... 19 common frames omitted
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jedisPoolFactory' defined in class path resource [com/imooc/miaosha/redis/RedisService.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [redis.clients.jedis.JedisPool]: Circular reference involving containing bean 'redisService' - consider declaring the factory method as static for independence from its containing instance. Factory method 'jedisPoolFactory' threw exception; nested exception is java.lang.NullPointerException
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:599) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1173) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1067) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:208) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1138) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	... 32 common frames omitted
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [redis.clients.jedis.JedisPool]: Circular reference involving containing bean 'redisService' - consider declaring the factory method as static for independence from its containing instance. Factory method 'jedisPoolFactory' threw exception; nested exception is java.lang.NullPointerException
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:189) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:588) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	... 44 common frames omitted
Caused by: java.lang.NullPointerException: null
	at com.imooc.miaosha.redis.RedisService.jedisPoolFactory(RedisService.java:88) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_211]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_211]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_211]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_211]
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:162) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	... 45 common frames omitted

其中Circular reference involving containing bean 'redisService' - consider declaring the factory method as static for independence from its containing instance.

redisService中出现了循环引用问题，为什么会有这个问题呢？因为RedisService中引用了jedisPool，但是jedisPool是一个实例化方法，也就是说创建JedisPoolFactory这个Bean时，是依赖RedisService的，RedisService中又注入了JedisPool，所以RedisService和jedisPool形成循环依赖。

起初为了方便将它们写在一起，解决方法是将jedisPool从Redis中拿出来，它们其实是没有关系的

package com.imooc.miaosha.redis;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Service;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;

@Service
public class RedisPoolFactory {

    @Autowired
    RedisConfig redisConfig;

    @Bean
    public JedisPool jedisPoolFactory(){     //@bean注解将bean注入到容器中
        JedisPoolConfig poolConfig = new JedisPoolConfig();
        poolConfig.setMaxIdle(redisConfig.getPoolMaxldle());
        poolConfig.setMaxTotal(redisConfig.getPoolMaxTotal());
        poolConfig.setMaxWaitMillis(redisConfig.getPoolMaxWait()*1000);
        JedisPool jp=new JedisPool(poolConfig,redisConfig.getHost(),redisConfig.getPort(),redisConfig.getTimeout()*1000,redisConfig.getPassword(),0);
        return jp;
    }
}

package com.imooc.miaosha.redis;

import com.alibaba.fastjson.JSON;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;

@Service
public class RedisService {

    @Autowired
    JedisPool jedisPool;

    public  T get(String key,Class clazz){

        Jedis jedis = null;     //连接池用完后一定要释放掉，不然导致连接不够用
        try{
            jedis=jedisPool.getResource();
            String str=jedis.get(key);
            T t=stringToBean(str,clazz);
            return t;
        }finally {
            returnToPool(jedis);
        }
    }

    public  boolean set(String key,T value){

        Jedis jedis = null;
        try{
            jedis=jedisPool.getResource();
            String str= beanToString(value);
            if(str==null||str.length()<=0){
                return  false;
            }
            jedis.set(key,str);
            return true;
        }finally {
            returnToPool(jedis);
        }
    }

    private  String beanToString(T value) {
        if (value == null) {         //加入value是int类型，无法通过json转化字符串，所以要判断
             return null;
        }
        Class clazz = value.getClass();
        if(clazz==int.class||clazz==Integer.class){     //先处理这几种，其它情况可日后根据情况再完善
           return ""+value;
        }else if(clazz==String.class){
           return (String)value;
        }else if(clazz==long.class||clazz==Long.class){
           return ""+value;
        }else{
            return JSON.toJSONString(value);
        }

    }

    private  T stringToBean(String str,Class clazz) {   //参数校验是必不可少的
        if(str==null||str.length()<=0||clazz==null)
            return null;
        if(clazz==int.class||clazz==Integer.class){
            return (T)Integer.valueOf(str);
        }else if(clazz==String.class){
            return (T)str;
        }else if(clazz==long.class||clazz==Long.class){
            return (T)Long.valueOf(str);
        }else{
            return JSON.toJavaObject(JSON.parseObject(str),clazz);
        }
    }

    private void returnToPool(Jedis jedis){
        if(jedis!=null){
            jedis.close();//返回连接池，并不会关闭，看源码可以知道
        }
    }
}