redis-springboot-redistemplate更改序列化方式，及解决一些问题

配置 springboot redis 使用 json 序列化遇到的问题，做下记录，具体见代码

import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;
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.GenericJackson2JsonRedisSerializer;

/**
 * class RedisConfig
 *
 * @author zhangyi 2021/3/29 18:35
 */
@Configuration
public class RedisConfig {

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

        //解决时间序列化的问题 —— org.springframework.data.redis.serializer.SerializationException: Could not read JSON: Cannot construct instance of `java.time.LocalDateTime` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
        ObjectMapper mapper = new ObjectMapper()
                .registerModule(new ParameterNamesModule())
                .registerModule(new Jdk8Module())
                .registerModule(new JavaTimeModule());
                
        //将默认的 @class 加上，解决 —— java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to 
        mapper.activateDefaultTyping(
                mapper.getPolymorphicTypeValidator(),
                ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.PROPERTY);
                
        //解决实体没有的字段导致反序列化失败 —— Caused by: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

        // 使用GenericJackson2JsonRedisSerializer 替换默认序列化
        GenericJackson2JsonRedisSerializer serializer = new GenericJackson2JsonRedisSerializer(mapper);

        template.setDefaultSerializer(serializer);
        template.setValueSerializer(serializer);
        template.setHashValueSerializer(serializer);
        
        //key序列化器，用上面的序列化器会使 key 长这个样子（"\"key_is_xxx\""，多了引号和反斜杠），下面的就不会了
        StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
        template.setKeySerializer(stringRedisSerializer);
        template.setHashKeySerializer(stringRedisSerializer);

        return template;
    }
}