[rules-dev] Questionable Exception Handling

[Zoltan Farkas]

This is my opinion also and is in line with the java best practices...

Based on javadoc(see class Error and Exception):

"The class Exception and its subclasses are a form of Throwable that indicates conditions that a reasonable application might want to catch. "

"An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch."

In all my apps I want my application to stop on a unrecoverable error (like OOM). However since most libraries have some catch(Throwable) in the code, I always have to use: 

-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=${DUMP_PATH} -XX:OnOutOfMemoryError="kill -9 %p"

For me as a user of the drools engine as a 3rd party I would expect that Error not be "hidden" inside a RuntimeException. For me Errors are something I cannot recover from... however I might choose to continue the application on a Exception ...

This is my opinion on this...

thanks

--zoly


________________________________________
From: rules-dev-bounces at lists.jboss.org [mailto:rules-dev-bounces at lists.jboss.org] On Behalf Of Geoffrey Wiseman
Sent: Friday, April 04, 2008 2:10 PM
To: Rules Dev List
Subject: Re: [rules-dev] Questionable Exception Handling

In most cases, I'd say that Errors shouldn't even be caught and rethrown, personally -- something like an OOME doesn't need additional object creation, for instance.
On Fri, Apr 4, 2008 at 1:55 PM, Mark Proctor <mproctor at codehaus.org> wrote:
I don't see a problem with Throwable there? We rethrow again, adding in some additional information. I found that just catching Exception didn't work as you could get verification errors and other stuch things. If you look at the context of that that method is doing too, its using reflection to instantiate a class.

Mark
Zoltan Farkas wrote: 
I was browsing through the drools source code 
 
I am not a fan of seeing catching Throwable in any java code ...
 
I see this in class org.drools.util.ClassUtils:
 
    /**
     * This method will attempt to create an instance of the specified Class. It uses
     * a syncrhonized HashMap to cache the reflection Class lookup.
     * @param className
     * @return
     */
    public static Object instantiateObject(String className) {
        Class cls = (Class) ClassUtils.classes.get( className );
        if ( cls == null ) {
            try {
                cls = Class.forName( className );
                ClassUtils.classes.put(  className, cls );
            } catch ( Throwable e ) {
                throw new RuntimeException("Unable to load class '" + className + "'", e );
            }            
        }
        
        Object object = null;
        try {
            object = cls.newInstance();            
        } catch ( Throwable e ) {
            throw new RuntimeException("Unable to instantiate object for class '" + className + "'", e );
        }  
        return object;
    }
 
I believe this masks important errors where the application should not continue to run and it would be preferable to crash...
 
--zoly
 
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Geoffrey Wiseman