Re: PostgreSQL types and Java types

Hi Andy,
Thank you very much for your reply! It's really helpful.
Maybe the PostgreSQL-JDBC crew should consider providing detailed
documentation about the data types...

Regards
MGP

> Hi Mario,
>
> As far as I'm aware there is no documentation around with an equivalent
> mapping, at least I've not seen one, but I'm a newbie to the Postgresql
> community myself. The postgresql driver is an almost fully compliant
> JDBC 3.0 level driver with some JDBC level 4.0 features. So other than
> the exclusions, http://jdbc.postgresql.org/todo.html, and the driver/db
> specific extensions,
> http://jdbc.postgresql.org/documentation/83/ext.html, you can pretty
> much derive the mappings, and if you get stuck, you can always jump into
> the source code of the driver. Any mapping is two step: from db to
> java.sql.Types to java. So you can get the java.sql.Types to java
> mapping from lots of online sources such as
> http://java.sun.com/j2se/1.4.2/docs/guide/jdbc/getstart/mapping.html#996858
>, or http://java.sun.com/javase/6/docs/api/java/sql/Types.html and the
> java.sql.Types to db mappings from the postgresql jdbc driver source code,
> http://jdbc.postgresql.org/download.html.
>
> When using the driver directly with jdbc from Java, I haven't
> experienced any problems with a wide range of data types. However
> Hibernate has been a whole different story. Its postgresql dialect is
> somewhat deficient. When attempting to do any reverse engineering,
> character types are mapped incorrectly to char[] and accordingly fail,
> while character varying gets correctly mapped to String. The new uuid
> data type gets mapped to either Serializable, byte[], or in some cases
> to b[ of which there is no actual java type, all of which is also
> incorrect, but also indicates that there are at least 3 distinct paths
> through the Hibernate reverse engineering code to derive three different
> java types from the one database type, one of which isn't even a type at
> all. So to get JPA/Hibernate working through the postgresql JDBC driver
> has taken some level of manual intervention and some database specific
> modifications in my code that limit the portability of the DAO layer.
>
> Let me know if I have not addressed your question or if you are still
> struggling with mapping issues, not that I'll necessarily be able to
> assist.
>
> Cheers,
>
> Andy
>
> mario(dot)g(dot)pavlov(at)gmail(dot)com wrote:
> > Hi list,
> > I'm sorry for asking this question, I'm sure it's been answered many
> > times but I didn't manage to find the answer anywhere.
> > So the question is how do PostgreSQL data types map to Java data types ?
> > I've found that MySQL answers this question very good:
> > http://dev.mysql.com/doc/refman/5.0/en/connector-j-reference-type-convers
> >ions.html I hope there is similar peace of documentation for PostgreSQL!
> >
> > thank you
> >
> > Regards
> > MGP