Running mvn shade on a pre-existing uber jar - maven

Question

I have a uber jar that's already generated (not via Maven; I just have the jar). I need to use it along with another jar, which has dependency conflicts. I'd like to shade all the libs in the first uber jar, except for a few classes which need to be public.
What is the setup to take an existing jar, and use Maven shade plugin to rename most (except for a whitelist) of its classes, generating a new uber jar?

Answer 1

You can do a "rename-all" type of activity with maven-shade-plugin. For example:
<relocations>
<relocation>
<pattern></pattern>
<shadedPattern>relocated.</shadedPattern>
<excludes>
<exclude>com.myfirm.level1.level2.*</exclude>
</excludes>
</relocation>
</relocations>
Will essentially move every package a.b.c to relocated.a.b.c (except for the explicit pattern I excluded).
It appears that the relocation process moves all references to classes that match that pattern, regardless if that class is defined within a dependency used to construct the jar.
The following stack trace (obtained from trying to run a main() defined in a jar that was constructed using the relocation above) shows that a reference to java.lang.Object was renamed to relocated.java.lang.Object, and that (obviously) the relocated. version can't be found.
java.lang.NoClassDefFoundError: relocated/java/lang/Object
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)
Caused by: java.lang.ClassNotFoundException: relocated.java.lang.Object
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
... 13 more
Exception in thread "main"