Re: [OJB-developers] Handling Exception

[Thomas M. <tho...@ho...>]

Hi Bertrand,

you are right, this is really annoying.
There is a prio 1 task on the todo list (No. 25) covering your request.
Now that the most important features for release 1.0 are implemented I
don't have any excuses not to start this task!
(of cause it's more fun to implement new features than to fix bugs....)

I hope work on this soon ;-)

cheers,

Thomas

ber...@wa... wrote:
> 
> Hi,
> 
> I have a problem with the way Obj handles exceptions.
> 
> For example,
> when I do a getIteratorByQuery(),  if something goes wrong with my database
> during a prepare statement
> the exception will be caught in StatementForClass::getPreparedStatement()
> that will print a trace on the console but I will
> receive a perfectly correct  Iterator that will return no element.
> In the program itself there is no way to tell the difference between such
> an error condition and a query that will return no element, if the program
> runs stand alone, the only way is to redirect standard output and go and
> look for error message.
> 
> I think it would be better for StatementForClass::getPreparedStatement to
> throw a new PersistenceBrokerException. That way the program could decide
> how to handle the error.
> Of course all the methods called along the chain should be modified so that
> they declare that they throw a PersistenceBrokerException and don't hide
> the exception themself.
> This should also make thinks easier for unit testing.
> 
> I modified the different methods for getIteratorByQuery() as an example.I
> have added a //!! comment in the different places where I made a change.
> 
> Of course many more methods do just the same as
> StatementForClass::getPreparedStatement() and many more changes will be
> needed.
> Because PersistenceBrokerException extends RuntimeException adding the
> throw clause isn't required but is it really a good idea to have all
> exception behaving as runtime exceptions. In the code there seems to be
> Methods that declare to throw the exception other that don't, sometime very
> similar methods like
> getIteratorByQuery() and getIteratorFromQuery().
> 
> If you think the change is worth it I could give you some help.
> 
> Bertrand
> 
> PersistenceBrokerImpl:
>     public Iterator getIteratorByQuery(Query query) throws
> PersistenceBrokerException
>     {
>         Class itemClass = query.getSearchClass();
>         ClassDescriptor cld =
> m_DescriptorRepository.getDescriptorFor(itemClass);
>         return getIteratorFromQuery(query, cld);
>     }
> 
>     private Iterator getIteratorFromQuery(Query query, ClassDescriptor mif)
> //!!
>     throws PersistenceBrokerException
>     {
> //!!
> /*        try
>         {
>             RsIterator iter = null;
>             iter = new RsIterator(query, mif, this);
>             return iter;
>         }
>         catch (Exception ex)
>         {
>             System.out.println("get iterator from query " + ex.getMessage
> ());
>             ex.printStackTrace();
>         }
>         return null;
> */
>             RsIterator iter = null;
>             iter = new RsIterator(query, mif, this);
>             return iter;
> 
>     }
> 
> RsIterator:
>     public RsIterator(Query query, ClassDescriptor mif,
> PersistenceBrokerImpl broker)
> //!!
>     throws PersistenceBrokerException
>     {
>         if (_debug)
>         {
>             System.out.println("RsIterator(" + query + ", " + mif + ")");
>         }
>         m_rs = new JdbcAccess(broker).executeQuery(query, mif);
>         m_broker = broker;
>         m_mif = mif;
>         itemProxyClass = mif.getProxyClass();
>     }
> 
> JdbcAccess
>     ResultSet executeQuery(Query query, ClassDescriptor mif)
> //!!
>     throws PersistenceBrokerException
>     {
>         if (_debug)
>         {
>             System.out.println("executeQuery: " + query);
>         }
>         try
>         {
>             // if query has criteria, use them in where clause
>             if (query.getCriteria() != null && !query.getCriteria().isEmpty
> ())
>             {
> 
>                 String sql = SqlGenerator.getInstance
> ().getPreparedSelectStatement(query, mif);
>                 PreparedStatement stmt = broker.getStatementManager
> ().getPreparedStatement(mif, sql);
>                 broker.getStatementManager().bindStatement(stmt,
> query.getCriteria(), mif, 1);
>                 ResultSet rs = stmt.executeQuery();
>                 // as we return the resultset for further operations, we
> cannot release the statement yet.
>                 // that has to be done by the JdbcAccess-clients (i.e.
> RsIterator, ProxyRsIterator and PkEnumeration.)
>                 return rs;
> 
>             }
>             // if query has no criteria, perform select * from table
>             else
>             {
>                 Statement stmt = broker.getStatementManager
> ().getGenericStatement(mif);
>                 String sql = SqlGenerator.getInstance
> ().getSelectStatementDep(query, mif);
>                 ResultSet rs = stmt.executeQuery(sql);
>                 return rs;
>             }
>         }
>         catch (Exception ex)
>         {
> //!!
>             System.out.println("execute query " + ex.getMessage());
> //            ex.printStackTrace();
> //            return null;
>             throw new PersistenceBrokerException( ex) ;
> 
>         }
>     }
> 
> StatementManager
>   public PreparedStatement getPreparedStatement(ClassDescriptor cds, String
> sql)
>   throws PersistenceBrokerException
>   {
>     return getStatementsForClass(cds).getPreparedStmt(sql);
>   }
> 
> StatementForClass
> public PreparedStatement getPreparedStmt(String sql)
> //!!!
> throws PersistenceBrokerException
> {
>         PreparedStatement stmt = null;
>         try
>         {
>             stmt = prepareStatement(sql);
>         }
>         catch (java.sql.SQLException ex)
>         {
> //!!!
>             System.err.println(ex.getMessage());
>             ex.printStackTrace();
>             throw new PersistenceBrokerException( ex) ;
>         }
>         return stmt;
> }
> 
> _______________________________________________
> Objectbridge-developers mailing list
> Obj...@li...
> https://lists.sourceforge.net/lists/listinfo/objectbridge-developers