Using AttribueConverter on a composite @JoinColumns in Hibernate-CodePudding

Hibernate (with Spring Boot JPA) fails to insert when the target entity is using a composite join where one of the columns is a custom type that uses a converter.

A simplified entities definition:

@Entity
data class MyConfiguration(
    @Id
    val configurationId: Long,
    val enabled: Boolean,
    @OneToMany(
        cascade = [CascadeType.ALL],
        fetch = FetchType.EAGER,
        orphanRemoval = true,
        mappedBy = "id.configurationId"
    )
    val tables: Set<SourceTable>
)

@Embeddable
data class SourceTableId(
    val configurationId: Long,
    @Convert(converter = TableIdConverter::class)
    val tableId: TableId
) : Serializable

@Entity
data class SourceTable(
    @EmbeddedId
    val id: SourceTableId,
    @OneToMany(
        cascade = [CascadeType.ALL],
        fetch = FetchType.EAGER,
        orphanRemoval = true
    )
    @JoinColumns(
        JoinColumn(name = "configurationId", referencedColumnName = "configurationId", updatable = false),
        JoinColumn(name = "tableId", referencedColumnName = "tableId", updatable = false)
    )
    val groupingFields: Set<TableGroupField> = emptySet()
)

@Embeddable
data class TableGroupFieldId(
    val configurationId: Long,
    @Convert(converter = TableIdConverter::class)
    val tableId: TableId,
    val fieldName: String
) : Serializable

@Entity
data class TableGroupField(
    @EmbeddedId
    val id: TableGroupFieldId
)

The converter class is using simple string operations, and the TableId class implements Serializable. When saving an element from the context of a Spring Boot application, I'm getting the following exception:

... Omitted for readability ...
Caused by: javax.persistence.RollbackException: Error while committing the transaction
    at org.hibernate.internal.ExceptionConverterImpl.convertCommitException(ExceptionConverterImpl.java:81) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:104) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:562) ~[spring-orm-5.3.8.jar:5.3.8]
    ... 33 common frames omitted
Caused by: java.lang.NullPointerException: Cannot invoke "java.util.Comparator.compare(Object, Object)" because the return value of "org.hibernate.type.descriptor.java.JavaTypeDescriptor.getComparator()" is null
    at org.hibernate.type.AbstractStandardBasicType.compare(AbstractStandardBasicType.java:211) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.type.ComponentType.compare(ComponentType.java:217) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
... Omitted for readability ...

I verified that changing the TableId column to a simple string resolves the issue. Is there anything else I should apply to make it work with this join query?

CodePudding user response：

Converters on the id or parts of the id only work by accident in this case. There is an open issue for this: https://hibernate.atlassian.net/browse/HHH-8820