How to use two versions of jar in my java project

Question

In my java project, I need to use neo4j-1.9.3 that depends on lucene-3.6.2, and ElasticSearch which depends on lucene-4.4.0. I know that if I want to use two versions of lucene directly, I can use ClassLoader to load different classes from the lucenes.

But the problem is that I won't use lucene's apis directly now. Is there any way that lucene-3.6.2 can be loaded when neo4j's apis are running, and lucene-4.4.0 can be loaded while running elasticsearch's apis. The two versions of lucene conflict now, and I need to run neo4j and elasticsearch in one project. How could I solve the dependency problem?

Thanks in advance.

Answer 1

You could still use a ClassLoader solution, but that is a nasty business where it is easy to make mistakes.

You could also use different JVM's.

But the solution I would personally choose is either (or both) of the following:

• Verify that Neo4J breaks with Lucene 4.x. Maybe you will get lucky and there won't be any problems using the latest version.
• Split them up into two applications where one of them, say Neo4J, is accessed by the other application via web service (most likely REST) calls. Neo4J has a built-in REST API anyway.

Answer 2

OSGi can fix this problem. An OSGi bundle is nothing more than a jar with additional metadata detailing versions. A bundle has a version number, and will detail version numbers (or ranges) of dependent jars.