Hibernate JPA DB2 Custom Data Type

Question

I am an unfortunate dev that needs to work with a very legacy database. The problem is, that the database contains custom datatypes:

CREATE DISTINCT TYPE SCHEMA.T_STUPID_ID AS
    SMALLINT WITH COMPARISONS
;

So I cannot change that, but need to get the data and query it. It appears that it does not work, cause when querying by Id (findOne) using spring data jpa (repository) I get the following error:

DB2 SQL Error: SQLCODE=-401, SQLSTATE=42818, SQLERRMC==, DRIVER=4.19.26

which is : THE DATA TYPES OF THE OPERANDS OF AN OPERATION ARE NOT COMPATIBLE So it sounds like the queries do not work with custom types :/

I also tried this way:

@Query("select p from ImSickOfThisEntity p where cast(p.entityId as integer) 
= ?1 ")

But I got:

 DB2 SQL Error: SQLCODE=-461, SQLSTATE=42846, SQLERRMC=IPSDBO.T_PRODUCT_ID;SYSIBM.INTEGER

which translates to :

A VALUE WITH DATA TYPE source-data-type CANNOT BE CAST TO TYPE target-data-type

How to deal with such custom types? Google is not helpful, I can only find custom Java types with standard database column types....

Answer 1

You'll need to implement a UserType and you can specify the sqlTypes.

public class SmallIntHibernateType implements UserType {

@Override
public int[] sqlTypes() {
    return new int[] {Types.SMALLINT};
}

@Override
public Class returnedClass() {
    return Integer.class;
}

@Override
public boolean equals(Object o, Object o2) throws HibernateException {
    if (o == null && o2 == null) {
        return true;
    } else if (o == null) {
        return false;
    } else if (o2 == null) {
        return false;
    } else {
        return ((Integer) o).intValue() == ((Integer) o2).intValue();
    }
}

@Override
public int hashCode(Object o) throws HibernateException {
    return o.hashCode();
}

@Override
public Object nullSafeGet(ResultSet resultSet, String[] strings, SharedSessionContractImplementor sessionImplementor, Object o) throws HibernateException, SQLException {
    return resultSet.getInt(strings[0]);
}

@Override
public void nullSafeSet(PreparedStatement preparedStatement, Object value, int index, SharedSessionContractImplementor sessionImplementor) throws HibernateException, SQLException {
    if (value == null || value.equals(0)) {
        preparedStatement.setNull(index, Types.INTEGER);
        return;
    }

    if (!(value instanceof Integer)) {
        throw new UnsupportedOperationException("can't convert " + value.getClass());
    }

    preparedStatement.setInt(index, ((Integer) value));
}

@Override
public Object deepCopy(Object value) throws HibernateException {
    if (value == null) {
        return null;
    }

    if (!(value instanceof Integer)) {
        throw new UnsupportedOperationException("can't convert " + value.getClass());
    }

    return value;
}

@Override
public boolean isMutable() {
    return false;
}

@Override
public Serializable disassemble(Object value) throws HibernateException {
    if (!(value instanceof Integer)) {
        throw new UnsupportedOperationException("can't convert " + value.getClass());
    }

    return (Integer) value;
}

@Override
public Object assemble(Serializable cached, Object owner) throws HibernateException {
    if (!(cached instanceof Integer)) {
        throw new UnsupportedOperationException("can't convert " + cached.getClass());
    }

    return cached;
}

@Override
public Object replace(Object original, Object target, Object owner) throws HibernateException {
    return original;
}
}

Then on your entity you'll need to specify the using the type.

@Id
@Type(type = "com.data.system.SmallIntHibernateType")
private int id;