[Java知识库]Redis-Java客户端-Spring Data Redis

一、介绍

二、使用（Springboot应用）

（1）引入Maven相关依赖（springboot对应redis依赖、连接池依赖）

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
            <version>2.3.4.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-pool2</artifactId>
            <version>2.11.1</version>
        </dependency>

注：默认的Java客户端依赖是lettuce

（2）编写配置文件application.properties

spring.redis.host=192.168.105.220
spring.redis.port=6379
spring.redis.password=123456
spring.redis.database=0
spring.redis.lettuce.pool.max-active=8
spring.redis.lettuce.pool.max-idle=8
spring.redis.lettuce.pool.min-idle=2
spring.redis.lettuce.pool.max-wait=1000ms

（3）运行测试

@SpringBootTest
class SpringbootRedisTestApplicationTests {

    @Autowired
    private RedisTemplate redisTemplate;

    @Test
    void contextLoads() {
        ValueOperations valueOperations = redisTemplate.opsForValue();
        valueOperations.set("name", "tom");
        Object name = valueOperations.get("name");
        System.out.println(name); 
    }

}

三、Redis序列化

（1）上述key存入时是name，但redis中显示xxxxxname，是因为Spring Data Redis默认使用jdkSerialization来序列化。

注：缺点是可读性差、占用内存大。

（2）自定义序列化方式解决上述问题
引入Maven相关依赖（因为Json序列化需要用到对应的Jar包）

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.13.3</version>
        </dependency>

创建配置类并更改默认的序列化器

@Configuration
public class RedisConfig {

    @Bean
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory){
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate();
        redisTemplate.setConnectionFactory(redisConnectionFactory);

        redisTemplate.setKeySerializer(RedisSerializer.string());
        redisTemplate.setHashKeySerializer(RedisSerializer.string());
        redisTemplate.setValueSerializer(RedisSerializer.json());
        redisTemplate.setHashValueSerializer(RedisSerializer.json());
        return redisTemplate;
    }
}

再次运行测试类

（3）上述序列化器转换对象为JSON字符串时，会额外存储对象的全类名（带来额外的内存开销）

@SpringBootTest
class SpringbootRedisTestApplicationTests {

    @Autowired
    private RedisTemplate redisTemplate;

    @Test
    void contextLoads() {
        ValueOperations valueOperations = redisTemplate.opsForValue();
        valueOperations.set("name2", new Person());
        Object tom = valueOperations.get("name2");
        System.out.println(tom); 
    }

}

@Data
@AllArgsConstructor
@NoArgsConstructor
class Person{
    private String name = "tom";
    private int age = 22;
}

四、通用序列化做法

（1）为了节省内存空间，存储值时通常不用JSON序列化器，改为统一使用String序列化器，当需要存储对象时，手动进行序列化及反序列化（普通字符串转JSON格式字符串）。
（2）配置key和value均用String序列化器

@Configuration
public class RedisConfig {

    @Bean
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory){
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate();
        redisTemplate.setConnectionFactory(redisConnectionFactory);

        redisTemplate.setKeySerializer(RedisSerializer.string());
        redisTemplate.setHashKeySerializer(RedisSerializer.string());
        redisTemplate.setValueSerializer(RedisSerializer.string());
        redisTemplate.setHashValueSerializer(RedisSerializer.string());
        return redisTemplate;
    }
}

（3）运行

@SpringBootTest
class SpringbootRedisTestApplicationTests {

    @Autowired
    private RedisTemplate redisTemplate;

    @Test
    void contextLoads() throws JsonProcessingException {
        ValueOperations valueOperations = redisTemplate.opsForValue();
        Person person = new Person();

        //获取SpringMVC提供的JSON转换器
        ObjectMapper objectMapper = new ObjectMapper();
        valueOperations.set("name3", objectMapper.writeValueAsString(person));
        String str = (String) valueOperations.get("name3");
        Person tom = objectMapper.readValue(str, Person.class);
        System.out.println(tom);
    }

}

@Data
@AllArgsConstructor
@NoArgsConstructor
class Person{
    private String name = "tom";
    private int age = 22;
}