RE: Exception handling Was: Future JDK features 2 items

2004-11-21 Thread RK

Can't we handle in this
try {
  
}catch (Exception e) {
  if( e instantceof JMSException ||
e instantceof RemoteException ||
e instance of SQLException){
  ...
 }
}

-Original Message-
From: Brett Porter [mailto:[EMAIL PROTECTED]
Sent: Sunday, November 21, 2004 4:26 AM
To: Jakarta General List
Subject: Re: Exception handling Was: Future JDK features 2 items


I'm in favour of the multiple exception catch. I think the common use
for this is to catch a series of checked exceptions in a certain way,
while avoiding catching unchecked exceptions which you want to
propogate.

This is a good thing, because often I've seen code that catches
Exception for brevity because it's considered to not be able to throw
anything else, and later a NullPointer crops up and gets swallowed by
the wrong handler, or a new checked exception gets introduced that is
also caught where different handling may have been appropriate.

As far as the common interface, I have no problem with the exception
in this case being a Throwable. I think the JVM assigning the greatest
common denominator base-class might be a little too much magic. And
as syntax is pretty crowded when you can do that in a cast in the
handler. But a lot of handlers are logging or wrapping in a new
exception so the type is irrelevant.

Cheers,
Brett

On Sat, 20 Nov 2004 14:45:37 -0500, Noel J. Bergman [EMAIL PROTECTED]
wrote:
try {
 
} catch( (JMSException | RemoteException | SQLException) e) {
}

   try {
 ...
   } catch (Exception e) {
 ...
   }

  Usually you don't want to just catch all exceptions in a single block.
  Instead you want to have clusters of exceptions

 And what is the common interface for those exceptions?  Exception?  ;-)
Are
 you looking for catch (TypeList As ParentType), and just want the JVM
to
 exclude out other types derived from ParentType?

 --- Noel




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Re: Exception handling Was: Future JDK features 2 items

2004-11-20 Thread Rainer Klute
Am Sa, 2004-11-20 um 08.31 schrieb Craig McClanahan:
 On Fri, 19 Nov 2004 23:21:02 -0800, Daniel Rall [EMAIL PROTECTED] wrote:
  On Fri, 2004-10-29 at 13:35 -0400, Henri Yandell wrote:
  ...
   How about just being able to do multiple Exceptions in one block?
  
   try {

   } catch(JMSException, RemoteException, SQLException e) {
   }
  
   or possibly even:
  
   try {

   } catch( (JMSException | RemoteException | SQLException) e) {
   }
  
  Something like this would be truly excellent.  I'm so sick of having to
  write 30 lines of exception handling code.
 
 How about two lines, which you can already do today?
 
 try {
   ...
 } catch (Exception e) {
   ...
 }

Craig,

I wouldn't have expected that answer from you. :-)

Usually you don't want to just catch all exceptions in a single block.
Instead you want to have clusters of exceptions like in the example
quoted above, and you want to handle each cluster of exceptions
differently.

And often the exception types you'd like to cluster don't have a
sensible inheritance relation other than that they subclass from
Exception.

Yes, we do need another catching syntax between the two extremes catch
everything in one and catch each exception type separately.

Best regards
Rainer Klute

   Rainer Klute IT-Consulting GmbH
  Dipl.-Inform.
  Rainer Klute E-Mail:  [EMAIL PROTECTED]
  K├Ârner Grund 24  Telefon: +49 172 2324824
D-44143 Dortmund   Telefax: +49 231 5349423

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Re: Exception handling Was: Future JDK features 2 items

2004-11-20 Thread Felipe Leme
On Sat, 2004-11-20 at 05:31, Craig McClanahan wrote:

 How about two lines, which you can already do today?
 
 try {
   ...
 } catch (Exception e) {
   ...
 }

The problem with such approach is that it catches all exception, checked
or not (see below)

 seems to be a standarized log it and exit or log it and rethrow it
 in a wrapper exception strategy, which you can deal with quite
 easily.

That makes sense for checked exceptions. For instance, when you use
reflection to invoke a method, you have to handle 2 or 3 checked
exceptions, which you typically want to just log and exit as you
described. But if you use a generic catch( Exception e ), you would
catch unchecked exception as well (like NullPointerException).

 Sheesh, hasn't anyone ever heard of inheritance around here?  :-)

Ask the java.lang folks :-)

I mean, there is a good 'inheritance chain' of

 Throwable - Exception - RuntimeException - TheException 

for unchecked exceptions, but for checked exceptions is just

 Throwable - Exception - TheException ; 

I think there is a missing class there. If we had something like this:

Throwable - Exception - UncheckedException - RuntimeException
Throwable - Exception - CheckedException

Or even just:

Throwable - Exception - RuntimeException
Throwable - Exception - CheckedException


Then your idea would make sense: we could just use the CheckedException,
without the need for changing the language sintaxe (just the API and
maybe some internal structures in the VM).


-- Felipe



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Re: Exception handling Was: Future JDK features 2 items

2004-11-20 Thread Brett Porter
I'm in favour of the multiple exception catch. I think the common use
for this is to catch a series of checked exceptions in a certain way,
while avoiding catching unchecked exceptions which you want to
propogate.

This is a good thing, because often I've seen code that catches
Exception for brevity because it's considered to not be able to throw
anything else, and later a NullPointer crops up and gets swallowed by
the wrong handler, or a new checked exception gets introduced that is
also caught where different handling may have been appropriate.

As far as the common interface, I have no problem with the exception
in this case being a Throwable. I think the JVM assigning the greatest
common denominator base-class might be a little too much magic. And
as syntax is pretty crowded when you can do that in a cast in the
handler. But a lot of handlers are logging or wrapping in a new
exception so the type is irrelevant.

Cheers,
Brett

On Sat, 20 Nov 2004 14:45:37 -0500, Noel J. Bergman [EMAIL PROTECTED] wrote:
try {
 
} catch( (JMSException | RemoteException | SQLException) e) {
}
 
   try {
 ...
   } catch (Exception e) {
 ...
   }
 
  Usually you don't want to just catch all exceptions in a single block.
  Instead you want to have clusters of exceptions
 
 And what is the common interface for those exceptions?  Exception?  ;-)  Are
 you looking for catch (TypeList As ParentType), and just want the JVM to
 exclude out other types derived from ParentType?
 
 --- Noel
 
 
 
 
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Re: Exception handling Was: Future JDK features 2 items

2004-11-19 Thread Daniel Rall
On Fri, 2004-10-29 at 13:35 -0400, Henri Yandell wrote:
...
 How about just being able to do multiple Exceptions in one block?
 
 try {
  
 } catch(JMSException, RemoteException, SQLException e) {
 }
 
 or possibly even:
 
 try {
  
 } catch( (JMSException | RemoteException | SQLException) e) {
 }

Something like this would be truly excellent.  I'm so sick of having to
write 30 lines of exception handling code.


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Re: Exception handling Was: Future JDK features 2 items

2004-11-19 Thread Craig McClanahan
On Fri, 19 Nov 2004 23:21:02 -0800, Daniel Rall [EMAIL PROTECTED] wrote:
 On Fri, 2004-10-29 at 13:35 -0400, Henri Yandell wrote:
 ...
  How about just being able to do multiple Exceptions in one block?
 
  try {
   
  } catch(JMSException, RemoteException, SQLException e) {
  }
 
  or possibly even:
 
  try {
   
  } catch( (JMSException | RemoteException | SQLException) e) {
  }
 
 Something like this would be truly excellent.  I'm so sick of having to
 write 30 lines of exception handling code.

How about two lines, which you can already do today?

try {
  ...
} catch (Exception e) {
  ...
}

If you really want to treat different types of exceptions differently,
you can special case by putting specialized catch blocks for the
special cases in front of this.  The predominant use case, though,
seems to be a standarized log it and exit or log it and rethrow it
in a wrapper exception strategy, which you can deal with quite
easily.

Sheesh, hasn't anyone ever heard of inheritance around here?  :-)

Craig

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Re: Exception handling Was: Future JDK features 2 items

2004-10-30 Thread Henning Schmiedehausen
On Fri, 2004-10-29 at 19:35, Henri Yandell wrote:

 2/
 How about just being able to do multiple Exceptions in one block?
 
 try {
  
 } catch(JMSException, RemoteException, SQLException e) {
 }
 
 or possibly even:
 
 try {
  
 } catch( (JMSException | RemoteException | SQLException) e) {
 }

+a bazillion. I like the first one better, though.

Regards
Henning



-- 
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[EMAIL PROTECTED]+49 9131 50 654 0   http://www.intermeta.de/

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Re: Exception handling Was: Future JDK features 2 items

2004-10-29 Thread sebb
On Fri, 29 Oct 2004 13:35:04 -0400 (EDT), Henri Yandell
[EMAIL PROTECTED] wrote:
 
 
 On Fri, 29 Oct 2004, Dain Sundstrom wrote:
 
  I actually love closures, and think it would be a great addition to Java.  I
  spend a lot of time tracking down poorly written try/finally blocks in
  people's code where they don't properly close DB connections, IO streams, Jar
  files, and even delete their temp files.   A good closure library would
  virtually eliminate this type of programming errors.
 
 1/
 How about the Perl6 finally system where you can attach a try/catch to
 variables?
 
 In Perl 6 it's:
 
  my $p = P.new;   POST { $p and $p.Done; }
 or
  my $p is post { .Done } = P.new;
 
 So in Java it could be something like:
 
 Connection conn = ds.getConnection(); finally(conn) { conn.close(); };
 Connection conn = ds.getConnection() @ { conn.close(); };
 Connection conn = ds.getConnection(); conn @ finally { conn.close(); };
 
 Biggest problem is that I can't see a way to write that nicely.
 
 2/
 How about just being able to do multiple Exceptions in one block?
 
 try {
  
 } catch(JMSException, RemoteException, SQLException e) {
 }

+1 That could save a lot of tedious repetition
 
 or possibly even:
 
 try {
  
 } catch( (JMSException | RemoteException | SQLException) e) {
 }
 
 The last one is interesting as it could be a larger concept allowing
 mixed-types; but from a finite set. Probably lots wrong with that idea :)
 
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FW: RE: Exception handling Was: Future JDK features 2 items

2004-10-29 Thread Dan Lydick



A definite +1 for multiple exceptions in a catch{} block.

I have had a number of times I have wanted to do this,

but have had to create a private method and refer all

catch{} blocks to it.





Dan Lydick



 [Original Message]

 From: Henri Yandell [EMAIL PROTECTED]

 To: Jakarta General List [EMAIL PROTECTED]

 Date: 10/29/04 12:38:48 PM

 Subject: Exception handling   Was: Future JDK features 2 items



 

 

 

 2/

 How about just being able to do multiple Exceptions in one block?

 

 try {

  

 } catch(JMSException, RemoteException, SQLException e) {

 }

 

 or possibly even:

 

 try {

  

 } catch( (JMSException | RemoteException | SQLException) e) {

 }

 

 The last one is interesting as it could be a larger concept allowing 

 mixed-types; but from a finite set. Probably lots wrong with that idea :)





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RE: Exception handling Was: Future JDK features 2 items

2004-10-29 Thread Gary Gregory
 try {
  
 } catch(JMSException, RemoteException, SQLException e) {
 }

+1

(We used to have something like that in Smalltalk)

Gary

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