How to create custom jsonb mapper for PostgreSQL and Hibernate in Kotlin?

Question

I went through available articles: 1, 2, 3.

All of the articles nail down to the following options:

• Register custom PostgreSQL95Dialect which has jsonb type
• Implement Hibernate's UserTypeinterface with custom mapping
• Annotate Entity with @TypeDef of custom implementation
• Define in application.properties custom dialect

If all of the above is done, code is supposed to work. In my case I bump into mysterious Unable to build Hibernate SessionFactory; nested exception is org.hibernate.MappingException: property mapping has wrong number of columns: com.example.Book.header type: com.example.hibernate.BookHeaderType which I don't understand how to debug further.

My JsonbType abstract class:

abstract class JsonbType : UserType {

    override fun hashCode(p0: Any?): Int {
        return p0!!.hashCode()
    }

    override fun deepCopy(p0: Any?): Any {
        return try {
            val bos = ByteArrayOutputStream()
            val oos = ObjectOutputStream(bos)
            oos.writeObject(p0)
            oos.flush()
            oos.close()
            bos.close()
            val bais = ByteArrayInputStream(bos.toByteArray())
            ObjectInputStream(bais).readObject()
        } catch (ex: ClassNotFoundException) {
            throw HibernateException(ex)
        } catch (ex: IOException) {
            throw HibernateException(ex)
        }
    }

    override fun replace(p0: Any?, p1: Any?, p2: Any?): Any {
        return deepCopy(p0)
    }

    override fun equals(p0: Any?, p1: Any?): Boolean {
        return p0 == p1
    }

    override fun assemble(p0: Serializable?, p1: Any?): Any {
        return deepCopy(p0)
    }

    override fun disassemble(p0: Any?): Serializable {
        return deepCopy(p0) as Serializable
    }

    override fun nullSafeSet(p0: PreparedStatement?, p1: Any?, p2: Int, p3: SharedSessionContractImplementor?) {
        if (p1 == null) {
            p0?.setNull(p2, Types.OTHER)
            return
        }
        try {
            val mapper = ObjectMapper()
            val w = StringWriter()
            mapper.writeValue(w, p1)
            w.flush()
            p0?.setObject(p2, w.toString(), Types.OTHER)
        } catch (ex: java.lang.Exception) {
            throw RuntimeException("Failed to convert Jsonb to String: " + ex.message, ex)
        }
    }

    override fun nullSafeGet(p0: ResultSet?, p1: Array<out String>?, p2: SharedSessionContractImplementor?, p3: Any?): Any {
        val cellContent = p0?.getString(p1?.get(0))
        return try {
            val mapper = ObjectMapper()
            mapper.readValue(cellContent?.toByteArray(charset("UTF-8")), returnedClass())
        } catch (ex: Exception) {
            throw RuntimeException("Failed to convert String to Jsonb: " + ex.message, ex)
        }
    }

    override fun isMutable(): Boolean {
        return true
    }

    override fun sqlTypes(): kotlin.IntArray? {
        return IntArray(Types.JAVA_OBJECT)
    }
}

My concrete class BookHeaderType looks:

class BookHeaderType : JsonbType() {

    override fun returnedClass(): Class<BookBody> {
        return BookBody::class.java
    }

}

CustomPostgreSQLDialect.kt:

class CustomPostgreSQLDialect : PostgreSQL95Dialect {

    constructor(): super() {
        this.registerColumnType(Types.JAVA_OBJECT, "jsonb")
    }
}

Book.kt entity:

@Entity
@Table(name = "book")
@TypeDefs(
        TypeDef(name = "BookHeaderType", typeClass = BookHeaderType::class)
)
data class Book(
        @Id
        @GeneratedValue(strategy = GenerationType.SEQUENCE)
        @Column(updatable = false, nullable = false)
        val id: Long,

        @Column(name = "header", nullable = false, columnDefinition = "jsonb")
        @Type(type = "BookHeaderType")
        var header: BookHeader
)

BookHeader.kt implements Serializable

@JsonIgnoreProperties(ignoreUnknown = true)
data class BookHeader(
    var createdAt: OffsetDateTime,
    var createdBy: String
) : Serializable {
    constructor() : this(OffsetDateTime.now(), "test")
}

What do I do wrong? Should jsonb custom type be created differently in Kotlin?

Answer 1

There is a sibling question that has the answer

You would need to use custom types:

pom.xml dependency:

<dependency>
    <groupId>com.vladmihalcea</groupId>
    <artifactId>hibernate-types-52</artifactId>
    <version>2.9.9</version>
</dependency>

Register Customer PostgreSQL dialect:

class CustomPostgreSQLDialect : PostgreSQL95Dialect {
  constructor() : super() {
    this.registerHibernateType(Types.OTHER, JsonNodeBinaryType::class.java.name)
    this.registerHibernateType(Types.OTHER, JsonStringType::class.java.name)
    this.registerHibernateType(Types.OTHER, JsonBinaryType::class.java.name)
    this.registerHibernateType(Types.OTHER, JsonNodeBinaryType::class.java.name)
    this.registerHibernateType(Types.OTHER, JsonNodeStringType::class.java.name)
  }
}

Option 1:

Annotate Entity with jsonb type and make jsonb as Map<String, Any>:

import com.example.demo.pojo.SamplePojo
import com.vladmihalcea.hibernate.type.json.JsonBinaryType
import com.vladmihalcea.hibernate.type.json.JsonStringType
import org.hibernate.annotations.Type
import org.hibernate.annotations.TypeDef
import org.hibernate.annotations.TypeDefs
import javax.persistence.*

@Entity
@Table(name = "tests")
@TypeDefs(
        TypeDef(name = "json", typeClass = JsonStringType::class),
        TypeDef(name = "jsonb", typeClass = JsonBinaryType::class)
)
data class SampleEntity (
    @Id @GeneratedValue
    val id: Long?,
    val name: String?,

    @Type(type = "jsonb")
    @Column(columnDefinition = "jsonb")
    var data: Map<String, Any>?
) {

    /**
     * Dependently on use-case this can be done differently:
     * https://stackoverflow.com/questions/37873995/how-to-create-empty-constructor-for-data-class-in-kotlin-android
     */
    constructor(): this(null, null, null)
}

You would need Pojo to Map serializer/deserializer.

Option 2:

Annotate Entity with jsonb type and make jsonb as JsonNode?:

import com.fasterxml.jackson.databind.JsonNode
import com.vladmihalcea.hibernate.type.json.JsonBinaryType
import com.vladmihalcea.hibernate.type.json.JsonStringType
import org.hibernate.annotations.Type
import org.hibernate.annotations.TypeDef
import org.hibernate.annotations.TypeDefs
import javax.persistence.*

@Entity
@Table(name = "tests")
@TypeDefs(
        TypeDef(name = "json", typeClass = JsonStringType::class),
        TypeDef(name = "jsonb", typeClass = JsonBinaryType::class)
)
data class SampleJsonNodeEntity (
        @Id @GeneratedValue
        val id: Long?,
        val name: String?,

        @Type(type = "jsonb")
        @Column(columnDefinition = "jsonb")
        var data: JsonNode?
) {

    /**
     * Dependently on use-case this can be done differently:
     * https://stackoverflow.com/questions/37873995/how-to-create-empty-constructor-for-data-class-in-kotlin-android
     */
    constructor(): this(null, null, null)
}

You would need custom POJO to JsonNode, assumingly Jackson serializer/deserializer.

Summary:

1st option is better when you have a big JSON with one level of indentation.

2nd option is better when you have nested objects in objects data-types.