getting error while try to generate signed APK android studio 3

Question

I am getting the following error when try to generate signed APK in android studio 3

 Error:trouble processing "javax/xml/namespace/QName.class":
Error:Ill-advised or mistaken usage of a core class (java.* or javax.*)
Error:when not building a core library.
Error:This is often due to inadvertently including a core library file
Error:in your application's project, when using an IDE (such as
Error:Eclipse). If you are sure you're not intentionally defining a
Error:core class, then this is the most likely explanation of what's
Error:going on.
Error:However, you might actually be trying to define a class in a core
Error:namespace, the source of which you may have taken, for example,
Error:from a non-Android virtual machine project. This will most
Error:assuredly not work. At a minimum, it jeopardizes the
Error:compatibility of your app with future versions of the platform.
Error:It is also often of questionable legality.
Error:If you really intend to build a core library -- which is only
Error:appropriate as part of creating a full virtual machine
Error:distribution, as opposed to compiling an application -- then use
Error:the "--core-library" option to suppress this error message.
Error:If you go ahead and use "--core-library" but are in fact
Error:building an application, then be forewarned that your application
Error:will still fail to build or run, at some point. Please be
Error:prepared for angry customers who find, for example, that your
Error:application ceases to function once they upgrade their operating
Error:system. You will be to blame for this problem.
Error:If you are legitimately using some code that happens to be in a
Error:core package, then the easiest safe alternative you have is to
Error:repackage that code. That is, move the classes in question into
Error:your own package namespace. This means that they will never be in
Error:conflict with core system classes. JarJar is a tool that may help
Error:you in this endeavor. If you find that you cannot do this, then
Error:that is an indication that the path you are on will ultimately
Error:lead to pain, suffering, grief, and lamentation.
Error:1 error; aborting
Error:Execution failed for task ':_4SaleApp:transformClassesWithDexForRelease'.
> com.android.build.api.transform.TransformException: com.android.ide.common.process.ProcessException: java.util.concurrent.ExecutionException: com.android.ide.common.process.ProcessException: Error while executing java process with main class com.android.dx.command.Main with arguments {--dex --num-threads=4 --multi-dex --main-dex-list /Volumes/Data/AMIRA/Work/Q84Sale/Q84Sale/_4SaleApp/build/intermediates/multi-dex/release/maindexlist.txt --output /Volumes/Data/AMIRA/Work/Q84Sale/Q84Sale/_4SaleApp/build/intermediates/transforms/dex/release/0 --min-sdk-version 16 /Volumes/Data/AMIRA/Work/Q84Sale/Q84Sale/_4SaleApp/build/intermediates/transforms/jarMerging/release/0.jar}

can anyone help please ?

Answer 1

The XPP answer did not work for me. Most of the cross-referenced answers ignore that this can be caused by other library dependencies (i.e. JARs/AARs). In my case this error was only appearing during the signed build -- unsigned builds were fine.

Running 'gradlew :[MY-PROJECT]:dependencies' shows the full dependency tree. If you find a dependency that uses a JAR or classes in the javax/java namespace, then you can add a gradle exclude statement to your dependency declaration, such as (gradle 4.1+):

api('my.favorite.dependency') { exclude group: 'javax' }

Then run the gradle ':dependencies' task again. You should see that the excluded dependency is now removed from the tree. If this dependency is required for compilation and not provided elsewhere, then the build*/assemble* tasks will fail. If the dependency is required at runtime and not provided elsewhere, for ex. by the OS, then the app. will compile and then fail at runtime with a "ClassNotFound" exception.

In the worst case, if the dependency tree isn't much help, then you may have to start commenting-out dependencies and the code that uses them, to find the culprit dependency. Hopefully the dependency that caused this error was barely used. Once you find the dependency that causes the error, you need to fix the situation one of two ways. Either replace the JAR/AAR with something that doesn't cause the error; or rebuild the dependency so that the javax/java classes are not exported with the JAR/AAR.