debug java jar file from command line?

Question

I cannot get command-line debugging with jdb to work on a Cucumber/Java jar file. I looked at this SO question for example, and so far nothing has worked.

• When I run the cucumber feature file from IntelliJ, it works just fine.
• I compiled the program according to the local directions, and that finished successfully.
• When I run the compiled jar file with java -jar runJar.jar , everything works just fine.

• When I run jdb runJar.jar , I get the jdb prompt:

  Initializing jdb ...

but when I try to run the Main-Class, it fails:

> run MainRunner
run  MainRunner
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
VM Started: Error: Could not find or load main class MainRunner

The application exited

I know that "MainRunner" is the correct class because that's the name of the "Main class:" in IntelliJ and also because I unzipped the jar file using this command:

unzip -c MyJar.jar META-INF/MANIFEST.MF | grep 'Main-Class

and it reports Main-Class: com.XXXXX.sdt.framework.runner.MainRunner as the Main-Class.

• If instead run MainRunner I type run com.XXXXX.sdt.framework.runner.MainRunner , then I get the error:

  VM Started: Error: Could not find or load main class com.XXXXX.sdt.framework.runner.MainRunner

• If I startup a JVM and then attach to it with:

  java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=1044 -jar runJar.jar

and

jdb -attach 1044

and resume after the main 1 prompt, I get the error

Exception occurred: java.lang.StringIndexOutOfBoundsException (uncaught)"thread=main", java.lang.String.charAt(), line=658 bci=21

The Java docs on jdb imply that this should just work, so I'm not sure where to go from here.

Answer 1

Did you notice that you are running runJar.jar but checked for the Main class in MyJar.jar ?

If you are using a JAR file as an application packaging, you need the Main-Class in that jar file, not in one of the jar files on your path.