On 3/29/06, Frank W. Zammetti <[EMAIL PROTECTED]> wrote: > > Hey all, > > I just spent about 20 minutes working through a problem with FileUpload... > turned out to be my fault entirely, I didn't include Commons IO (FYI, I'm > not seeing a dependency list on the FileUpload site... maybe I missed it).
You did. See: http://jakarta.apache.org/commons/fileupload/dependencies.html This is the standard location for the dependency list for all Commons components. The problem is, it was one of those aggrevating problems to track down > because the stack trace didn't reveal the actual line where the failure > occured, and catching Exception didn't get triggered. I wound up catching > Throwable, and I was then able to figure it out. The stack trace should have shown a NoClassDefFoundError indicating a class in Commons IO. I haven't seen a situation where that's not the case, and that's also been the case for all of the people who've asked about it on the list, at least that I can recall. I know that missing dependencies is always a b**ch, and they tend to be > these annoying problems with no error messages or anything (sure, a > debugger helps, but that doesn't seem like the best answer to me). So, I > have a suggestion that could well go all across Commons, or any other > project for that matter. > > In Java Web Parts, we've gotten into the habit of putting this in all > classes: > > /** > * This static initializer block tries to load all the classes this one > * depends on (those not from standard Java anyway) and prints an error > * meesage if any cannot be loaded for any reason. > */ > static { > try { > Class.forName("org.apache.commons.logging.Log"); > Class.forName("org.apache.commons.logging.LogFactory"); > } catch (ClassNotFoundException e) { > System.err.println("CacheControlFilter" + > " could not be loaded by classloader because classes it depends" + > " on could not be found in the classpath..."); > e.printStackTrace(); > } > } Aside from the fact that Class.forName is generally not a good idea in a J2EE environment, I personally have a strong dislike for static initialisers, so I'm not inclined to do something like this for components I work on. Other folks may like it, though. ;-) -- Martin Cooper It's just echoing the import list, minus classes found in the SDK (if > that's missing, you aren't getting *this* far!). This saves a lot of time > and headache when you are missing a dependency. I know that adds > something additional to maintain in the class, but it seems a fair > trade-off to me. > > Does anyone see this as being something that might be helpful for Commons? > If there is a better way to get the same effect I'm all ears too (I could > see setting a string to the name of the class being checked so that it > could be output as part of the error message, but I'm talking about a > whole other way to check for dependencies). > > -- > Frank W. Zammetti > Founder and Chief Software Architect > Omnytex Technologies > http://www.omnytex.com > AIM: fzammetti > Yahoo: fzammetti > MSN: [EMAIL PROTECTED] > Java Web Parts - > http://javawebparts.sourceforge.net > Supplying the wheel, so you don't have to reinvent it! > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > >
