背景
在对 BSON 的 ObjectId 类型与 Java 的 LocalDate 类型进行序列化与反序列化时，Redis 出现了无法对 ObjectId、LocalDate 进行序列化的报错。
配置 ReactiveRedisTemplate<String, Object>于是作者决定在 Redis 的配置类中对 ReactiveRedisTemplate<String, Object> 进行定制，在阅读源码后发现 ReactiveRedisTemplate 的构造函数中可以传入一个 RedisSerializationContext<String, Object> 对象，对 Redis 序列化方式进行定制：
@Bean public ReactiveRedisTemplate<String, Object> reactiveRedisTemplate( ReactiveRedisConnectionFactory reactiveRedisConnectionFactory, RedisSerializationContext<String, Object> redisSerializationContext) { // 配置 RedisSerializationContext return new ReactiveRedisTemplate<>(reactiveRedisConnectionFactory, redisSerializationContext); } 配置 RedisSerializationContext<String, Object>查看 RedisSerializationContext<K, V> 接口对源码后，发现其内部有一个静态接口 RedisSerializationContextBuilder<K, V>，专门用于构建 RedisSerializationContext<K, V> 对象，其 key()、value()、hashKey()、hashValue() 等方法支持对序列化方式进行定制化：
/** * Builder for {@link RedisSerializationContext}. * * @author Mark Paluch * @author Christoph Strobl */ interface RedisSerializationContextBuilder<K, V> { ... }于是对 RedisSerializationContext<String, Object> 进行定制，使用自定义的序列化方式对 Redis 的 value 与 hashValue 进行特制的序列化：
@Bean public RedisSerializationContext<String, Object> redisSerializationContext() { RedisSerializationContext.RedisSerializationContextBuilder<String, Object> builder = RedisSerializationContext.newSerializationContext(); builder.key(StringRedisSerializer.UTF_8); builder.value(serializer()); // 设置自定义序列化 builder.hashKey(StringRedisSerializer.UTF_8); builder.hashValue(serializer()); // 设置自定义序列化 return builder.build(); }发现 RedisSerializationContext.RedisSerializationContextBuilder<String, Object> 接口的 value(...) 与 hashValue(...) 方法需要传入一个 RedisSerializer 对象，根据之前的项目经验，决定对其实现类 Jackson2JsonRedisSerializer 进行定制。
定制 Jackson2JsonRedisSerializer 的 ObjectMapper在 Jackson2JsonRedisSerializer 类中，发现有一个 ObjectMapper 类型的字段，根据其在 deserialize 方法与 serialize 方法中被调用的方式，不难猜出其负责对象的映射，故选择对 ObjectMapper 也进行定制化：
@SuppressWarnings("unchecked") public T deserialize(@Nullable byte[] bytes) throws SerializationException { if (SerializationUtils.isEmpty(bytes)) { return null; } try { return (T) this.objectMapper.readValue(bytes, 0, bytes.length, javaType); } catch (Exception ex) { throw new SerializationException("Could not read JSON: " + ex.getMessage(), ex); } } @Override public byte[] serialize(@Nullable Object t) throws SerializationException { if (t == null) { return SerializationUtils.EMPTY_ARRAY; } try { return this.objectMapper.writeValueAsBytes(t); } catch (Exception ex) { throw new SerializationException("Could not write JSON: " + ex.getMessage(), ex); } }在 ObjectMapper 中发现了一个 registerModule 方法，支持定制序列化器与反序列化器：
/** * Method for registering a module that can extend functionality * provided by this mapper; for example, by adding providers for * custom serializers and deserializers. * * @param module Module to register */ public ObjectMapper registerModule(Module module) { ... } 将定制的 Module 注册进 ObjectMapper 使用 JavaTimeModule 序列化 LocalDate 类Module 是一个 abstruct class，在其子类中，找到了 JavaTimeModule 类，其支持对 LocalDate 等时间类进行序列化，故将 JavaTimeModule 对象注册进 ObjectMapper 对象：
objectMapper.registerModule(new JavaTimeModule()); 定制 SimpleModule 序列化 ObjectId 类但是未找到对 BSON 的 ObjectId 类型进行序列化的 Module，于是构造一个 SimpleModule 对象，调用 addSerializer(...) 与 addDeserializer(...) 方法进行序列化与反序列化的定制（在此使用 ObjectId 的十六进制形式的字符串进行序列化），并将其注册进 ObjectMapper 对象：
SimpleModule objectIdModule = new SimpleModule("ObjectIdModule"); objectIdModule.addSerializer(ObjectId.class, new JsonSerializer<ObjectId>() { @Override public void serialize(ObjectId objectId, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { jsonGenerator.writeString(objectId.toString()); } }); objectIdModule.addDeserializer(ObjectId.class, new JsonDeserializer<ObjectId>() { @Override public ObjectId deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException { return new ObjectId(jsonParser.readValueAs(String.class)); } }); objectMapper.registerModule(objectIdModule);至此，完成 Redis 对 ObjectId 与 LocalDate 类进行定制的工作。
Redis 配置文件 package cn.tzq0301.auth.config; import com.fasterxml.jackson.annotation.JsonAutoDetect; import com.fasterxml.jackson.annotation.PropertyAccessor; import com.fasterxml.jackson.core.JsonGenerator; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.*; import com.fasterxml.jackson.databind.jsontype.impl.LaissezFaireSubTypeValidator; import com.fasterxml.jackson.databind.module.SimpleModule; import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule; import org.bson.types.ObjectId; import org.springframework.boot.SpringBootConfiguration; import org.springframework.context.annotation.Bean; import org.springframework.data.redis.connection.ReactiveRedisConnectionFactory; import org.springframework.data.redis.core.ReactiveRedisTemplate; import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer; import org.springframework.data.redis.serializer.RedisSerializationContext; import org.springframework.data.redis.serializer.StringRedisSerializer; import java.io.IOException; /** * @author tzq0301 * @version 1.0 */ @SpringBootConfiguration public class RedisConfig { public static final String PROJECT_NAMESPACE_PREFIX = "pcs:"; public static final String USER_NAMESPACE_PREFIX = PROJECT_NAMESPACE_PREFIX + "user:"; @Bean public ReactiveRedisTemplate<String, Object> reactiveRedisTemplate( ReactiveRedisConnectionFactory reactiveRedisConnectionFactory, RedisSerializationContext<String, Object> redisSerializationContext) { return new ReactiveRedisTemplate<>(reactiveRedisConnectionFactory, redisSerializationContext); } @Bean public RedisSerializationContext<String, Object> redisSerializationContext() { RedisSerializationContext.RedisSerializationContextBuilder<String, Object> builder = RedisSerializationContext.newSerializationContext(); builder.key(StringRedisSerializer.UTF_8); builder.value(serializer()); builder.hashKey(StringRedisSerializer.UTF_8); builder.hashValue(serializer()); return builder.build(); } private Jackson2JsonRedisSerializer<Object> serializer() { Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer<>(Object.class); ObjectMapper objectMapper = new ObjectMapper(); // ObjectId SimpleModule objectIdModule = new SimpleModule("ObjectIdModule"); objectIdModule.addSerializer(ObjectId.class, new JsonSerializer<ObjectId>() { @Override public void serialize(ObjectId objectId, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { jsonGenerator.writeString(objectId.toString()); } }); objectIdModule.addDeserializer(ObjectId.class, new JsonDeserializer<ObjectId>() { @Override public ObjectId deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException { return new ObjectId(jsonParser.readValueAs(String.class)); } }); objectMapper.registerModule(objectIdModule); // LocalDate objectMapper.registerModule(new JavaTimeModule()); objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY); objectMapper.activateDefaultTyping(LaissezFaireSubTypeValidator.instance, ObjectMapper.DefaultTyping.NON_FINAL); jackson2JsonRedisSerializer.setObjectMapper(objectMapper); return jackson2JsonRedisSerializer; } }
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