springboot中使用Redis解决高并发的方法

柔光的暖阳◎ 2022-11-10 14:27 203阅读 0赞

# 一、集成redis #

### 1、引入redis的依赖 ###

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-redis</artifactId>
            </dependency>

### 2、yml中配置redis地址、端口、密码 ###

redis:
        # redis密码
        password:
        alone:
          #redis地址
          host: 127.0.0.1
          #redis端口
          port: 6379

### 3、在server中使用redis ###

首先实体类要实现序列化  
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##### 简单实现redis缓存和查询功能 #####

@Service
    public class SysUserService { 
    	//自动注入redis
    	@Autowired
        private RedisTemplate<Object,Object> redisTemplate;
    
    	//根据用户id获取用户信息
    	 public SysUser selectSysUserByUserId(Integer userId){ 
            //修改key的序列化类型 提高可读行 StringRedisSerializer设置key的类型为string
            RedisSerializer redisSerializer = new StringRedisSerializer();
            redisTemplate.setKeySerializer(redisSerializer);
    
            //从redis缓存中查询
            SysUser sysUser = (SysUser) redisTemplate.opsForValue().get("sysUser");
            //如果为空则从数据库查询
            if(sysUser == null){ 
                //从数据库查询
                 sysUser = sysUserDao.selectSysUserByUserId(userId);
                 //存入redis中
                 redisTemplate.opsForValue().set("sysUser",sysUser);
            }
            return sysUser;
        }
    }

##### 解决高并发问题 #####

第一种：效率最慢。在方法前面加上synchronized ，使用同步锁去锁定请求。当同时有一千条数据请求时，只能一条一条请求的进来。

public synchronized SysUser selectSysUserByUserId(Integer userId){ 
            //修改key的序列化类型 提高可读行 StringRedisSerializer设置key的类型为string
            RedisSerializer redisSerializer = new StringRedisSerializer();
            redisTemplate.setKeySerializer(redisSerializer);
    
            //从redis缓存中查询
            SysUser sysUser = (SysUser) redisTemplate.opsForValue().get("sysUser");
            if(sysUser == null){ 
                //从数据库查询
                 sysUser = sysUserDao.selectSysUserByUserId(userId);
                 redisTemplate.opsForValue().set("sysUser",sysUser);
            }
            return sysUser;
        }

##### 第二种：效率比第一种高点，可以适用请求量不大的场景下。 #####

public  SysUser selectSysUserByUserId(Integer userId){ 
            //修改key的序列化类型 提高可读行 StringRedisSerializer设置key的类型为string
            RedisSerializer redisSerializer = new StringRedisSerializer();
            redisTemplate.setKeySerializer(redisSerializer);
    
            //从redis缓存中查询
            SysUser sysUser = (SysUser) redisTemplate.opsForValue().get("sysUser");
    
            //双重监测锁
            if(sysUser == null){ 
                synchronized (this){ 
                    if(sysUser == null){ 
                        //从数据库查询
                        sysUser = sysUserDao.selectSysUserByUserId(userId);
                        redisTemplate.opsForValue().set("sysUser",sysUser);
                    }
                }
            }
    
            return sysUser;
        }

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