Invalid or corrupt JAR File built by Maven shade plugin

Question

After adding the Maven jFree dependency to my existing application, I\'m not able to execute the created jar.

The only error message I get is the following:

Answer 1

I ran mvn dependency:tree with your setup and it will give a difference when you move the org.apache.poi higher up in the dependency declarations.

This is taken from the Introduction to the Dependency Mechanism regarding dependency order:

Dependency mediation - this determines what version of a dependency will be used when multiple versions of an artifact are encountered. Currently, Maven 2.0 only supports using the "nearest definition" which means that it will use the version of the closest dependency to your project in the tree of dependencies. You can always guarantee a version by declaring it explicitly in your project's POM. Note that if two dependency versions are at the same depth in the dependency tree, until Maven 2.0.8 it was not defined which one would win, but since Maven 2.0.9 it's the order in the declaration that counts: the first declaration wins.

There seems to be a conflict in your dependency resolution and that is causing your corrupt jar file (don't know why it gets corrupt).

Anyway, here are the diffs between the two poms (left is origin, right is with org.apache.poi higher up):

(Maybe it is hard to see at the pictures but if you zoom in you will see.)

The big difference is that in the non-working pom the org.apache.httpcomponents:httpcore:jar:4.2.1 has a dependency on commons-codec:commons-codec:jar:1.6, and in the working pom that dependency has been overriden with commons-codec:commons-codec:jar:1.5.

I guess that there is a problem with the 1.6 version of commons-codec together with org.apache.poi:poi:jar:3.8 which needs the 1.5 version.

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Edit

After this excellent answer that explains why the jar file is corrupt (too many entries in the jar) I just want to add a simple solution that at least works for your particular problem.

Add the tag true to your maven-shade-plugin configuration.

After that your java -jar target/com.mycompany.test-1.0.0-SNAPSHOT.jar command line will work.