CODEWITHSUNDEEP
mavenmaven-2
Sudoer
Sudoer

Reputation: 451

Dependency on two versions of a Jar

I have a module X that is dependent on a Third party library which in turn depends on apache-commons-collections 2.1.

In module X, I want to use the latest apache-commons-collections 3.0 which has some additional methods than 2.1. If I add a dependency to 3.0, I'm guessing this will create a problem since the class loader just picks up the first class it sees in the classpath. Is there a good way to get around this problem?

Thanks, S

Upvotes: 0

Views: 104

Answers (2)

Michał Kalinowski
Michał Kalinowski

Reputation: 17933

IMHO there is no really good way without additional solution for modularity (like Java EE's EAR or OSGi). I guess however that you're asking about just simple web (or not) module that directly use this 3rd party lib. I'm afraid you have to resolve this conflict manually. If fact, Maven won't provide 2 versions of commons-collections and depend on classloader's resolution, but rather resolve dependencies graph and pick the version it guess it's better with your POMs' declarations in mind. That means, if you declare in module X dependency on commons-collections version 3.0, that version will be used since this declaration is more important than some 3rd party lib's dependencies.

That's a serious problem of Java Platform itself, cousing such problems like the famous JAR hell. Unfortunately, it is your problem to choose and declare commons-collections version that satisfy both you and your 3rd party lib.

Upvotes: 1

Manfred Moser
Manfred Moser

Reputation: 29912

Just add the dependency to 3.0 to your project and it will prefer it over the older version of 2.1. To be explicit you can add an exclusion. In any case use the dependency plugin and the analyze and tree goals to see what is happening.

Long story short... this happens all the time and will be fine and in any case you can control what happens.

Upvotes: 0

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