HibernateでPostgreSQLLTREE列をマッピングするときにエラーが発生する

次のように、JavaでカスタムLTreeTypeクラスを実装します。

public class LTreeType implements UserType {

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

    @SuppressWarnings("rawtypes")
    @Override
    public Class returnedClass() {
        return String.class;
    }

    @Override
    public boolean equals(Object x, Object y) throws HibernateException {
        return x.equals(y);
    }

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

    @Override
    public Object nullSafeGet(ResultSet rs, String[] names, Object owner)
            throws HibernateException, SQLException {
        return rs.getString(names[0]);
    }

    @Override
    public void nullSafeSet(PreparedStatement st, Object value, int index)
            throws HibernateException, SQLException {
        st.setObject(index, value, Types.OTHER);
    }

    @Override
    public Object deepCopy(Object value) throws HibernateException {
        return new String((String)value);
    }

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

    @Override
    public Serializable disassemble(Object value) throws HibernateException {
        return (Serializable)value;
    }

    @Override
    public Object assemble(Serializable cached, Object owner)
            throws HibernateException {
        return cached;
    }

    @Override
    public Object replace(Object original, Object target, Object owner)
            throws HibernateException {
        // TODO Auto-generated method stub
        return deepCopy(original);
    }

}

そして、次のようにEntityクラスに注釈を付けます。

    @Column(name = "path", nullable = false, columnDefinition = "ltree")
    @Type(type = "LTreeType")
    private String path;