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Can taking a backup in WEB-INF/lib foo.jar to foo_backup.jar will effect in project?

What my exact question is...

If I do above kind of thing, will it load both jar? foo.jar and foo_backup.jar?

And as both jar contains same classes inside it. Which will be considered when I use some class (consider com.test.TestClass)? Will it be of foo.jar or foo_backup.jar?

can any one please advice on same? I can remove that foo_backup.jar but I want to know what will happen if this kind of scenario?

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    why can't you just change the extension so that it won't get picked up? Commented Dec 6, 2012 at 15:10
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    fvu is right, short answer better to change extension. Long answer: If you change the name but keep the jar extension, both files will be valid for class loading. If they're both in the classpath, the 1st jar that the classloader picks will be the one from classes are loaded. Also why are you doing a backup inside web-inf/lib? Can't you just copy the jar to somewhere else? Commented Dec 6, 2012 at 15:20
  • Yes you guys right and thanks for your answer. Actually it's creating an issue for me. Currently I can't think of which particular jar from list of similar(backup) jar is being called. I will implement this idea to change an ext. But my another question can't we check now which lib is used at run time? Any way? Commented Dec 6, 2012 at 15:32
  • @KetanISM: at runtime to know from where a class file has been loaded check it's code location through protection domain like the following: someInstance.getClass().getProtectionDomain().getCodeSource().getLocation() Commented Dec 6, 2012 at 17:24

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Instead of foo_backup.jar, create a backup with name like foo.jar.backup.

Still if you go with backup as foo_backup.jar then I think foo.jar will be loaded first as it comes first in the listing but still suspect, it may lead into issues(assuming backup is older version) as both the jars and hence the classes inside it would be available in the class path.

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I think the classloader will just pick the first one and load only that, but it will depend on the implementation of the classloader, which is not typically something you have much control over. This can lead to all sorts of nasty bugs. I'd suggest using @fvu's suggestion.

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It's definitely a good practice to call an back-up with name(-data).bak The data is in parenthesis as is optional, because it is useful in case you are going to have more than one backup so you can track your most recent ones.

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