JPA Hibernate Call Postgres Function Void Return MappingException:

This could be a hack, but it worked for me and is pretty simple. Just change the query to:

SELECT count(*) FROM your_function();

Now it returns a proper integer and hibernate is happy.

I had enough messing around with JPA trying to get it to run a stored procedure.

I ended up using JDBC with a prepared statement. I did it in 15 minutes after spending several fruitless hours trying to fit a square peg into a round hole. I called the same jndi datasource my persistence unit uses to get a connection, created a prepared statement and closed it when done.

So if you need to run a stored procedure (or Postgres function) from a (now mostly) JPA app, here is what worked for me:

@Stateless
@LocalBean
public class UserQueryBean implements Serializable {

    @Resource(mappedName="jdbc/DatabasePool") 
    private javax.sql.DataSource ds;

    ...

    public void runRequestCleanup() {

        String queryString = "SELECT cleanup_function_that_hibernateJPA_choked_on()";
        Connection conn = null;
        PreparedStatement statement = null;
        try {
            conn = ds.getConnection();
            statement = conn.prepareCall(queryString);
            statement.executeQuery();
        } catch (SQLException ex) {
            Logger.getLogger(UserQueryBean.class.getName()).log(Level.SEVERE, null, ex);
        }finally{
            try {
                statement.close();
                conn.close();
            } catch (SQLException ex) {
                Logger.getLogger(UserQueryBean.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
        // bit of logging code here    
    }
    ...
}

There seems to be a horrible oversight to leave out the simple ability to run a function or stored procedure on the server from JPA; especially one that doesn't return anything except void or the number of rows affected. And if it was deliberate ... no comment.

Edit: added close connection.