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Subject: When to catch exceptions (was Re: svn commit: r390198)
From: Thorsten Scherler <thorsten@apache.org>
To: Forrest Developers List <dev@forrest.apache.org>
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References: <20060330180517.48821.qmail@minotaur.apache.org>
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Date: Tue, 04 Apr 2006 01:56:27 +0200
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El jue, 30-03-2006 a las 18:05 +0000, thorsten@apache.org escribi=C3=B3:
> Author: thorsten
> Date: Thu Mar 30 10:05:15 2006
> New Revision: 390198
>=20
> URL: http://svn.apache.org/viewcvs?rev=3D390198&view=3Drev
> Log:
> Testing whether the source exists rather to throw an exception. One shoul=
d not throw/catch exception that are predictable.
>=20
> Modified:
>     forrest/trunk/main/java/org/apache/forrest/sourcetype/SourceTypeActio=
n.java
>=20
> Modified: forrest/trunk/main/java/org/apache/forrest/sourcetype/SourceTyp=
eAction.java
> URL: http://svn.apache.org/viewcvs/forrest/trunk/main/java/org/apache/for=
rest/sourcetype/SourceTypeAction.java?rev=3D390198&r1=3D390197&r2=3D390198&=
view=3Ddiff
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D
> --- forrest/trunk/main/java/org/apache/forrest/sourcetype/SourceTypeActio=
n.java (original)
> +++ forrest/trunk/main/java/org/apache/forrest/sourcetype/SourceTypeActio=
n.java Thu Mar 30 10:05:15 2006
> @@ -61,10 +61,10 @@
>              throw new Exception("SourceTypeAction: src attribute should =
be defined and non-empty.");
>          Source source =3D sourceResolver.resolveURI(src);
>          XMLPullParser parser =3D new Xerces2();
> -        try {
> -          InputStream is =3D source.getInputStream();
> -          parser.setInputSource(new XMLInputSource(null, src, null, is, =
null));
> -        } catch (SourceNotFoundException e) {
> +        if (source.exists()) {
> +            InputStream is =3D source.getInputStream();
> +            parser.setInputSource(new XMLInputSource(null, src, null, is=
, null));
> +        } else {
>            getLogger().warn("Source '"+source+"' not found");
>            return null;
>          }
>=20

We have lots of cases in our code like this example.=20

There are a lot of classes that are rather catching exceptions then
prevent to raise them. That is bad and we should remove this whenever
possible. Please if you find code like the above in our base send us an
enhancement patch. ;)

An exception (error) should not be provoced by purpose since it disrupts
the processing and is wasting speed.

TIA

http://java.sun.com/docs/books/tutorial/essential/exceptions/index.html
"What Is an Exception? - The Java programming language uses exceptions
to provide error-handling capabilities for its programs. An exception is
an event that occurs during the execution of a program that disrupts the
normal flow of instructions."

http://www.javaworld.com/javaworld/jw-08-2001/jw-0803-exceptions.html?
"The proper use of exceptions can make your programs easier to develop
and maintain, freer from bugs, and simpler to use. When exceptions are
misused, the opposite situation prevails: programs perform poorly,
confuse users, and are harder to maintain."

salu2
--=20
thorsten

"Together we stand, divided we fall!"=20
Hey you (Pink Floyd)