67-Redis

Redis主要用于处理数据的高效访问以及热点数据存储
1原子性单线程，  只是通过多线程优化了网络IO操作，执行命令仍然是单线程的，通过指令的单线程操作从而避免了冲突问题的出现。
2持久化
3redis底层良好的数据结构设计Redis3.2
//要停止原来的服务 net stop Redis 
//删除原来的服务 sc delete Redis 
//安装新的 
redis-server --service-install redis.windows.conf --loglevel verbose
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
修改application.yml，配置redis连接信息
spring:可以是字符串、整数、**浮点数类型 
  redis:
    host: 192.168.200.151
    port: 6379
添加redis配置类
package com.itheima.reggie.config; 
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.jsontype.impl.LaissezFaireSubTypeValidator;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;

//添加配置类 用来保证
@Configuration
public class RedisConfig {

    @Bean
    public RedisTemplate redisTemplate(RedisConnectionFactory redisConnectionFactory){
        RedisTemplate redisTemplate = new RedisTemplate();
        redisTemplate.setConnectionFactory(redisConnectionFactory);

        //设置一些redis的属性
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        //解决Redis value的序列化方式
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer =new Jackson2JsonRedisSerializer(Object.class);
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.activateDefaultTyping(LaissezFaireSubTypeValidator.instance,ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.WRAPPER_ARRAY);
        jackson2JsonRedisSerializer.setObjectMapper(objectMapper);
        redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
        redisTemplate.setHashKeySerializer(new StringRedisSerializer());
        redisTemplate.setHashValueSerializer(jackson2JsonRedisSerializer);

        return redisTemplate;
    }
}
@SpringBootTest
@RunWith(SpringRunner.class)
public class RedisTest {

    @Autowired
    private RedisTemplate redisTemplate;

    //String
    //添加数据
    @Test
    public void addInfo(){
        redisTemplate.opsForValue().set("name","zhangsan");
        //设置过期时间
        redisTemplate.opsForValue().set("age",18,5, TimeUnit.SECONDS);
    }

    //获取数据
    @Test
    public void getInfo(){
        redisTemplate.opsForValue().get("name");
    }

    //删除数据
    @Test
    public void setExpire(){
        redisTemplate.delete("name");
    }
}
以商品详情页为例，假设现在客户端有大量请求在查询商品详情信息， 如果直接基于数据库查询的话，则很有可能因为数据库性能问题，造成系统响应速度过慢，甚至宕机。那么此时则可以基于Redis进行改造。  
@Service
public class GoodsServiceImpl implements GoodsService {

    @Autowired
    private GoodsMapper goodsMapper;

    @Autowired
    private RedisTemplate redisTemplate;

    @Override
    public GoodsEntity findGoodsInfoById(Long goodsId) {
存在redis ,不存在mysql,mysql存在存redis,mysql不存在返回null
        //先查询缓存
        GoodsEntity redisGoods = (GoodsEntity) redisTemplate.opsForValue().get("goods:" + goodsId);
        if (redisGoods!= null){
            return redisGoods;
        }

        GoodsEntity goodsEntity = goodsMapper.selectById(goodsId);
        //存入缓存
        redisTemplate.opsForValue().set("goods:"+goodsId,goodsEntity);

        return goodsEntity;
    }
}