一、redisTemplate和stringRedisTemplate对比

RedisTemplate看这个类的名字后缀是Template，如果了解过Spring如何连接关系型数据库的，大概不会难猜出这个类是做什么的 ，它跟JdbcTemplate一样封装了对Redis的一些常用的操作，当然StringRedisTemplate跟RedisTemplate功能类似那么肯定就会有人问，为什么会需要两个Template呢，一个不就够了吗？其实他们两者之间的区别主要在于他们使用的序列化类。

RedisTemplate使用的是 JdkSerializationRedisSerializer 序列化对象
StringRedisTemplate使用的是 StringRedisSerializer 序列化String

1、StringRedisTemplate

• 主要用来存储字符串，StringRedisSerializer的泛型指定的是String。当存入对象时，会报错 ：can not cast into String。
• 可见性强，更易维护。如果过都是字符串存储可考虑用StringRedisTemplate。

2、RedisTemplate

• 可以用来存储对象，但是要实现Serializable接口。
• 以二进制数组方式存储，内容没有可读性。

二、redisTemplate序列化方式比较

那有没有办法，可以序列化对象，可读性又强呢？

• 1、手动转化成json串再存储。取出数据需要反序列化。
• 2、使用其他序列化方式。

spring-data-redis提供如下几种选择：

• GenericToStringSerializer: 可以将任何对象泛化为字符串并序列化
• Jackson2JsonRedisSerializer: 跟JacksonJsonRedisSerializer实际上是一样的
• JacksonJsonRedisSerializer: 序列化object对象为json字符串
• JdkSerializationRedisSerializer: 序列化java对象
• StringRedisSerializer: 简单的字符串序列化

1、性能测试对比

 @Testpublic void testSerial(){UserPO userPO = new UserPO(1111L,"小明_testRedis1",25);List<Object> list = new ArrayList<>();for(int i=0;i<200;i++){list.add(userPO);}JdkSerializationRedisSerializer j = new JdkSerializationRedisSerializer();GenericJackson2JsonRedisSerializer g = new GenericJackson2JsonRedisSerializer();Jackson2JsonRedisSerializer j2 = new Jackson2JsonRedisSerializer(List.class);Long j_s_start = System.currentTimeMillis();byte[] bytesJ = j.serialize(list);System.out.println("JdkSerializationRedisSerializer序列化时间："+(System.currentTimeMillis()-j_s_start) + "ms,序列化后的长度：" + bytesJ.length);Long j_d_start = System.currentTimeMillis();j.deserialize(bytesJ);System.out.println("JdkSerializationRedisSerializer反序列化时间："+(System.currentTimeMillis()-j_d_start));Long g_s_start = System.currentTimeMillis();byte[] bytesG = g.serialize(list);System.out.println("GenericJackson2JsonRedisSerializer序列化时间："+(System.currentTimeMillis()-g_s_start) + "ms,序列化后的长度：" + bytesG.length);Long g_d_start = System.currentTimeMillis();g.deserialize(bytesG);System.out.println("GenericJackson2JsonRedisSerializer反序列化时间："+(System.currentTimeMillis()-g_d_start));Long j2_s_start = System.currentTimeMillis();byte[] bytesJ2 = j2.serialize(list);System.out.println("Jackson2JsonRedisSerializer序列化时间："+(System.currentTimeMillis()-j2_s_start) + "ms,序列化后的长度：" + bytesJ2.length);Long j2_d_start = System.currentTimeMillis();j2.deserialize(bytesJ2);System.out.println("Jackson2JsonRedisSerializer反序列化时间："+(System.currentTimeMillis()-j2_d_start));}

结果：

JdkSerializationRedisSerializer序列化时间：8ms,序列化后的长度：1325
JdkSerializationRedisSerializer反序列化时间：4
GenericJackson2JsonRedisSerializer序列化时间：52ms,序列化后的长度：17425
GenericJackson2JsonRedisSerializer反序列化时间：60
Jackson2JsonRedisSerializer序列化时间：4ms,序列化后的长度：9801
Jackson2JsonRedisSerializer反序列化时间：4

2、性能总结

• JdkSerializationRedisSerializer序列化后长度最小，Jackson2JsonRedisSerializer效率最高。
• 如果综合考虑效率和可读性，牺牲部分空间，推荐key使用StringRedisSerializer，保持的key简明易读；value可以使用Jackson2JsonRedisSerializer
• 如果空间比较敏感，效率要求不高，推荐key使用StringRedisSerializer，保持的key简明易读；value可以使用JdkSerializationRedisSerializer

3、方案一、考虑效率和可读性，牺牲部分空间

package com.example.demo.config.redisConfig;import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
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;@Configuration
public class RedisConfig {@Bean(name = "redisTemplate")public RedisTemplate<String, Object> getRedisTemplate(RedisConnectionFactory factory) {RedisTemplate<String, Object> redisTemplate = new RedisTemplate<String, Object>();redisTemplate.setConnectionFactory(factory);redisTemplate.setKeySerializer(new StringRedisSerializer()); // key的序列化类型Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);ObjectMapper objectMapper = new ObjectMapper();objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);jackson2JsonRedisSerializer.setObjectMapper(objectMapper);redisTemplate.setValueSerializer(jackson2JsonRedisSerializer); // value的序列化类型return redisTemplate;}
}

注： new Jackson2JsonRedisSerializer(Object.class)需要指明类型，例如：new Jackson2JsonRedisSerializer(User.class)，否则会报错：

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.example.demo.bean.User。

或者开启默认类型：

 ObjectMapper objectMapper = new ObjectMapper();objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);jackson2JsonRedisSerializer.setObjectMapper(objectMapper);

这种方式存储时会自动带上类的全路径，占用部分空间：

4、方案二、空间敏感，忽略可读性和效率影响

@Configuration
public class RedisConfig {@Bean(name = "redisTemplate")public RedisTemplate<String, Object> getRedisTemplate(RedisConnectionFactory factory) {RedisTemplate<String, Object> redisTemplate = new RedisTemplate<String, Object>();redisTemplate.setConnectionFactory(factory);redisTemplate.setKeySerializer(new StringRedisSerializer()); // key的序列化类型redisTemplate.setValueSerializer(new JdkSerializationRedisSerializer()); // value的序列化类型return redisTemplate;}
}

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注：该方式，对象需要实现接口：Serializable

5、使用示例

@RunWith(SpringRunner.class)
@SpringBootTest
@WebAppConfiguration
public class RedisTest {@Resourceprivate RedisTemplate redisTemplate;@Testpublic void testRedis1(){User user = new User();user.setAge(11);user.setName("我是小王1");redisTemplate.opsForValue().set("user37",user);System.out.println(redisTemplate.getValueSerializer());System.out.println(redisTemplate.getKeySerializer());User result = (User) redisTemplate.opsForValue().get("user37");System.out.println(result);}
}

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SpringBoot中RedisTemplate更改序列化方式

可以通过手动配置, 将RedisTemplate的序列化方式进行更改

package com.wenbronk.data.redis;import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
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;@SpringBootApplication
public class RedisApplication {public static void main(String[] args) {SpringApplication.run(RedisApplication.class, args);}/*** redisTemplate 序列化使用的jdkSerializeable, 存储二进制字节码, 所以自定义序列化类* @param redisConnectionFactory* @return*/@Beanpublic RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory) {RedisTemplate<Object, Object> redisTemplate = new RedisTemplate<>();redisTemplate.setConnectionFactory(redisConnectionFactory);// 使用Jackson2JsonRedisSerialize 替换默认序列化Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);ObjectMapper objectMapper = new ObjectMapper();objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);jackson2JsonRedisSerializer.setObjectMapper(objectMapper);// 设置value的序列化规则和 key的序列化规则redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);redisTemplate.setKeySerializer(new StringRedisSerializer());redisTemplate.afterPropertiesSet();return redisTemplate;}
}