Question

So I’m trying to make a grails app that hooks into an existing DB where the primary key column is a UUID:

      Column       |            Type             | Modifiers 
-------------------+-----------------------------+-----------
 uuid              | uuid                        | not null

However, when I set up my data source like this:

class DataStore {
UUID     uuid
...
static mapping = {
...
     id generator: 'assigned', name: 'uuid', type: 'pg-uuid'
}

It insists that the uuid column is a varchar(255). I’m not sure what I have to do to make it recognize that the uuid column is a uuid column, and I’ve tried putting a UserType class in src/groovy/, but that didn’t fix anything.

I’m also trying to do the same with an inet column, but I figure one step at a time here.

Any help here? I’m at wit’s end.

Edit: I found this grails using uuid as id and mapping to to binary column , but it just throws this error when I try to run it now:

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Invocation of init method failed; nested exception is org.codehaus.groovy.grails.exceptions.GrailsDomainException: Error evaluating ORM mappings block for domain [cstools.domain.DataStore]:  No such property: UUIDUserType for class: org.codehaus.groovy.grails.orm.hibernate.cfg.HibernateMappingBuilder
... 23 more

UUIDUserType.groovy

import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.UUID;
import org.hibernate.HibernateException;

public class UUIDUserType implements org.hibernate.usertype.UserType {

    private static final String CAST_EXCEPTION_TEXT = " cannot be cast to a java.util.UUID.";

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#assemble(java.io.Serializable,
     *      java.lang.Object)
     */
    public Object assemble( Serializable cached, Object owner ) throws HibernateException {

        if ( !String.class.isAssignableFrom( cached.getClass() ) ) {
            return null;
        }

        return UUID.fromString( (String) cached );
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#deepCopy(java.lang.Object)
     */
    public Object deepCopy( Object value ) throws HibernateException {

        if ( !UUID.class.isAssignableFrom( value.getClass() ) ) {
            throw new HibernateException( value.getClass().toString() + CAST_EXCEPTION_TEXT );
        }

        UUID other = (UUID) value;

        return UUID.fromString( other.toString() );
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#disassemble(java.lang.Object)
     */
    public Serializable disassemble( Object value ) throws HibernateException {

        return value.toString();
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#equals(java.lang.Object,
     *      java.lang.Object)
     */
    public boolean equals( Object x, Object y ) throws HibernateException {

        if ( !UUID.class.isAssignableFrom( x.getClass() ) ) {
            throw new HibernateException( x.getClass().toString() + CAST_EXCEPTION_TEXT );
        }
        else if ( !UUID.class.isAssignableFrom( y.getClass() ) ) {
            throw new HibernateException( y.getClass().toString() + CAST_EXCEPTION_TEXT );
        }

        UUID a = (UUID) x;
        UUID b = (UUID) y;

        return a.equals( b );
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#hashCode(java.lang.Object)
     */
    public int hashCode( Object x ) throws HibernateException {
        if ( !UUID.class.isAssignableFrom( x.getClass() ) ) {
            throw new HibernateException( x.getClass().toString() + CAST_EXCEPTION_TEXT );
        }

        UUID a = (UUID) x;

        return a.hashCode();
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#isMutable()
     */
    public boolean isMutable() {

        return false;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#nullSafeGet(java.sql.ResultSet,
     *      java.lang.String[], java.lang.Object)
     */
    public Object nullSafeGet( ResultSet rs, String[] names, Object owner ) throws HibernateException, SQLException {

        String value = rs.getString( names[0] );
        if ( value == null ) {
            return null;
        }
        else {
            return UUID.fromString( value );
        }
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#nullSafeSet(java.sql.PreparedStatement,
     *      java.lang.Object, int)
     */
    public void nullSafeSet( PreparedStatement st, Object value, int index ) throws HibernateException, SQLException {

        if ( value == null ) {
            st.setNull( index, Types.VARCHAR );
            return;
        }

        if ( !UUID.class.isAssignableFrom( value.getClass() ) ) {
            throw new HibernateException( value.getClass().toString() + CAST_EXCEPTION_TEXT );
        }

        st.setString( index, value.toString() );
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#replace(java.lang.Object,
     *      java.lang.Object, java.lang.Object)
     */
    public Object replace( Object original, Object target, Object owner ) throws HibernateException {

        if ( !UUID.class.isAssignableFrom( original.getClass() ) ) {
            throw new HibernateException( original.getClass().toString() + CAST_EXCEPTION_TEXT );
        }

        return UUID.fromString( original.toString() );
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#returnedClass()
     */
    @SuppressWarnings( "unchecked" )
    public Class returnedClass() {

        return UUID.class;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.hibernate.usertype.UserType#sqlTypes()
     */
    public int[] sqlTypes() {

        return int[] { Types.CHAR };
    }
}

Answer 1

EDIT: This solution requires PostgreSQL 8.4 or higher, the according JDBC driver 8.4-703 or higher and Hibernate 3.6 (for the built-in pg-uuid type, a custom UserType should work with prior Hibernate versions)

Just found out that you don’t need a custom UserType to map java.util.UUID to a PostgreSQL uuid. Since Hibernate 3.6 you can use the built-in type pg-uuid which is a shortcut for org.hibernate.type.PostgresUUIDType (see the Hibernate 3.6 docs about basic types). This built-in type should exactly do what a custom UserType might do.

But I think you must use a uuid2 generator instead of the uuid generator. See the Hibernate 3.6 docs about generators. The uuid generator creates a String representation of the UUID, whereas the uuid2 generator is capable of generating values as java.util.UUID, java.lang.String or as a byte array of length 16 (byte[16]). I don’t know how to configure the uuid2 generator, though. I do not use this generator but just assign a random UUID in the constructor of my Entity base class.

So, I think you must change your code to the following:

class DataStore {
UUID     uuid
...
static mapping = {
...
  id generator: 'assigned', name: 'uuid2', type: 'pg-uuid'
}