Re: [Geotools-gt2-users] semantic error in DataStoreFinder

[<bu...@me...>]

Hi Jody,

My soultion is to enclose only the canProcess() in a try-catch block, 
and save the result of it in a boolean variable. Then decide wether a 
factory can handle a specific db based on the value of this boolean. But 
a few lines of code tells more than tousand words:

while (ps.hasNext()) {
     fac = (DataStoreFactorySpi) ps.next();

     boolean canProcess = false;

     try {
         canProcess = fac.canProcess(params);
     } catch (Throwable t) {
         /** The logger for the filter module. */
         LOGGER.log( Level.WARNING, "Could not acquire 
"+fac.getDescription()+":"+t, t );            	
         // Protect against DataStores that don't carefully
         // code canProcess
         continue;
     }

     if (canProcess) {
         return fac.createDataStore(params);
     }
}


This way an exception from canProcess() is silently ignored, but a real 
connection error is thrown back to the caller.

Best,
Peter

PS: attached is the same as a patch against SVN head.

Jody Garnett írta:
> Thanks Peter - or rather good "catch"
> 
> Can you cut and paste the modified code for me? I would be happy to 
> review and think about this change.
> We do have a common problem where data store implementors say they 
> canProcess, but then they really cannot. This has resulted in a very 
> unhappy GeoServer community on occasion.
> 
> If I understand the need:
> - you would like a decent failure reported when you cannot connect
> - we cannot afford to let a single bad apple ruin the batch
> Jody
>> Hi!
>>
>> In the SVN HEAD version DataStoreFinder.getDataStore(...) the whole 
>> canProcess(...), createDataStore(...) cycle is in a try {} 
>> catch(Throwable t) block. This way if a DataStore can handle a type of 
>> database, but fails to open it (e.g. corrupt db file) no exception is 
>> thrown, only a debug message is logged. This contradicts with the 
>> javadoc, which says that an IOException is thrown "If a suitable 
>> loader can be found, but it can not be attached to the specified 
>> resource without errors." And even the comment in the catch block 
>> states that it "Protect against DataStores that don't carefully code 
>> canProcess".
>>
>> I modifyed my copy in a way that only the canProcess(..) is in a 
>> try-catch block, but I think the SVN version should be modified also. 
>> The same allpies to FileDataStoreFinder also.
>>
>> Greetings,
>> Peter
>>
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