How to debug java-buildpack

[T0nyMa]

I am going to extend buildpack for our own app - modifying some customized properties files via buildpack.

My question is how to debug the buildpack, as I can not get sufficient information to narrow down errors.
For example, if I set heap size settings in java_opts.yml, it will fail because they should set in jre.yml. But what I get from cf cli is just "Checking status of app 'beacon-test'...Application failed to stage" even with --debug.

Is there any way to output more information? or Is there any better ways to build customized buildpack?

Thanks,

[nebhale]

Actually, this question recently came up on the vcap-dev mailing list. That's a better place to discuss this kind of thing anyway so take a look at this post on JBP_LOG_LEVEL and this one on running buildpacks locally.

As this is something that buildpack users will most likely do often, I'll keep this issue open to extend the documentation with discussion about it.