Problem in deserialize redis-cache to objects in Spring-boot

Question

I use JsonNode in my Client class to deal with a field with JSON type in MySQL 8 database. It works very well even with API requests. But when I enable caching with Redis (which I really need it), I notice that Redis is not able to serialize JsonNode. I searched the internet for changing the serialization method of Redis. and came up with the following code:

@Configuration
@EnableCaching
public class RedisConfig {

    @Bean
    @Primary
    public ObjectMapper objectMapper() {
        return Jackson2ObjectMapperBuilder.json()
                .serializationInclusion(JsonInclude.Include.NON_NULL) // Don’t include null values
                .featuresToDisable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS) //ISODate
                .build();
    }

    @Bean
    public RedisTemplate getRedisTemplate(ObjectMapper objectMapper, RedisConnectionFactory redisConnectionFactory){
        RedisTemplate redisTemplate = new RedisTemplate<>();
        redisTemplate.setDefaultSerializer(new GenericJackson2JsonRedisSerializer(objectMapper));
        redisTemplate.setConnectionFactory(redisConnectionFactory);
        return redisTemplate;
    }

    @Bean
    @Primary
    public RedisCacheConfiguration defaultCacheConfig(ObjectMapper objectMapper) {
        return RedisCacheConfiguration.defaultCacheConfig()
                .serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(new StringRedisSerializer()))
                .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new GenericJackson2JsonRedisSerializer(objectMapper)));
    }

}

It serializes my objects successfully and put them in Redis successfully, but cannot to deserialize them!. And produces the following error:

java.lang.ClassCastException: class java.util.LinkedHashMap cannot be cast to class com.example.Client (java.util.LinkedHashMap is in module java.base of loader 'bootstrap'; com.example.Client is in unnamed module of loader org.springframework.boot.devtools.restart.classloader.RestartClassLoader @4683d900)]

And this is my client class:

@Data
@Entity
@Table( name = "clients" )
@EntityListeners(AuditingEntityListener.class)
@TypeDef(name = "json", typeClass = JsonStringType.class)
public class Client  {
    /**
     * Id of the user
     */
    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY )
    private Long id;
    /**
     * UUID of the user.
     */
    @Column( name = "uuid", unique = true, updatable = false, nullable = false )
    private String uuid;


    /**
     * Name of the client
     */
    @Column( name = "name", unique = true, nullable = false )
    @Size( min=4, max=128, message = "client.exception.name.size" )
    @NotBlank( message = "client.exception.name.isBlank" )
    private String name;


    /**
     * Status of the client. Each client could have several statues.
     * 1.
     */
    @Column( name = "client_status_id" )
    @NotNull( message = "client.exception.status.isNull" )
    @Enumerated( EnumType.ORDINAL )
    private ClientStatus clientStatus = ClientStatus.Undefined;


    /**
     * Email address of the client.
     */
    @Column( name = "email" )
    @NotBlank( message = "client.exception.email.isBlank")
    @Size( min=5, max = 128, message = "client.exception.email.size")
    @Email( message = "client.exception.email.notValid" )
    private String email;

    /**
     * ClientNotFoundByIdException's phone number.
     */
    @Column( name = "phone" )
    @NotBlank( message = "client.exception.phone.isBlank" )
    @Size( min=3, max = 32, message = "client.exception.phone.size")
    @Phone( message = "client.exception.phone.notValid" )
    private String phone;

    /**
     * Whether client is active or not.
     */
    @Column( name = "is_active" )
    private Boolean isActive = true;

    /**
     * Default timezone of the client.
     */
    @Column( name = "timezone" )
    @NotBlank( message = "client.exception.timezone.isBlank" )
    @Size( min = 4, max = 64, message = "client.exception.timezone.size" )
    @TimeZone( message = "client.exception.timezone.notValid" )
    private String timezone;


    /**
     * Country code of the client in ISO 3166-2
     */
    @Column( name = "country" )
    @NotBlank( message = "client.exception.country.isBlank" )
    @Size( min = 2, max = 4, message = "client.exception.country.size" )
    @Country( message = "client.exception.country.notValid" )
    private String country;


    @Column( name = "language" )
    @NotBlank( message = "client.exception.language.isBlank" )
    @Size( min = 2, max = 3, message = "client.exception.language.size" )
    @Language
    private String language;


    /**
     * Extra fields for client in json
     */
    @Column( name = "fields", columnDefinition = "json" )
    @Type( type = "json" )
    @NotNull( message = "client.exception.fields.isNull" )
    private JsonNode fields;


    /**
     * Creation time of the record.
     */
    @Column( name = "created_at", updatable = false )
    @NotNull( message = "client.exception.createdAt.isNull")
    @CreatedDate
    private Instant createdAt;


    /**
     * The user that created the record.
     */
    @CreatedBy
    @ManyToOne
    @JoinColumn( name = "created_by" )
    private User createdBy;


    /**
     * In which time the record is modified.
     */
    @Column( name = "updated_at" )
    @NotNull( message = "client.exception.updatedAt.isNull" )
    @LastModifiedDate
    private Instant updatedAt;


    /**
     * By whom the record is modified.
     */
    @LastModifiedBy
    @ManyToOne
    @JoinColumn( name = "updated_by" )
    private User updatedBy;


    /**
     * The time in which the record is deleted.
     */
    private Instant deletedAt;


    /**
     * By whom the record is deleted.
     */
    @ManyToOne
    @JoinColumn( name = "deleted_by" )
    private User deleteBy;


    /**
     * Version of the record.
     */
    @Version
    private Long version;
}

Update:

I noticed tht the error is not related to JsonNode, It throws the exception when I use GenericJackson2JsonRedisSerializer.

Answer 1

Solved it by defining a custom ReadingConverter and WritingConverter. With those two, I was able to successfully deserialize properties of type JsonNode.

import com.fasterxml.jackson.databind.JsonNode
import com.fasterxml.jackson.databind.ObjectMapper
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import org.springframework.core.convert.converter.Converter
import org.springframework.data.convert.ReadingConverter
import org.springframework.data.convert.WritingConverter
import org.springframework.data.redis.core.convert.RedisCustomConversions
import org.springframework.data.redis.repository.configuration.EnableRedisRepositories
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer
import org.springframework.stereotype.Component

@WritingConverter
@Component
class JsonNodeToByteArrayConverter() : Converter<JsonNode, ByteArray> {

        private var serializer: Jackson2JsonRedisSerializer<JsonNode> = Jackson2JsonRedisSerializer(JsonNode::class.java)

    init {
        serializer.setObjectMapper(ObjectMapper())
    }

    override fun convert(source: JsonNode): ByteArray {
        return serializer.serialize(source)
    }
}

@ReadingConverter
@Component
class ByteArrayToJsonNodeConverter : Converter<ByteArray, JsonNode> {

        private var serializer: Jackson2JsonRedisSerializer<JsonNode> = Jackson2JsonRedisSerializer(JsonNode::class.java)

    init {
        serializer.setObjectMapper(ObjectMapper())
    }

    override fun convert(source: ByteArray): JsonNode {
        return serializer.deserialize(source)
    }
}

/**
 * Custom mappers are needed to convert JsonNode (otherwise, deserialization fails)
 */
@Configuration
@EnableRedisRepositories
class RedisConfiguration {
    @Bean
    fun redisCustomConversions(
        byteArrayToJsonNodeConverter: ByteArrayToJsonNodeConverter,
        jsonNodeToByteArrayConverter: JsonNodeToByteArrayConverter
    ): RedisCustomConversions {
        return RedisCustomConversions(listOf(byteArrayToJsonNodeConverter, jsonNodeToByteArrayConverter))
    }
}

Answer 2

I had very similar problem and the solution was strange, but simple - remove devtools dependency.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <optional>true</optional>
</dependency>