java_binary rule not adding main class to the manifest?

[Rohit Saboo]

Hi all,

I tried creating a java_binary rule, but for some reason the value of the main-class attribute is not being added to the manifest file in the jar. This doesn't matter if I run the java program via the generated launcher script. However, it's an issue if I have to run via the jar file.

Is this a known issue, and is there a workaround for this in the interim?

Thanks,

Rohit

[Alex Humesky]

You'll want to build the deploy jar for your binary, by adding "_deploy.jar" to your target name. That will create a jar with the binary's class files and the class files of the dependencies of that binary, and it should add the main class to the jar's manifest.

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[Alex Humesky]

That is, if you have a java_binary(name = "Test", ...), you can do "bazel build mypackage:Test_deploy.jar"

[Rohit Saboo]

Ah okay. Is there a way to ask Bazel to generate the deploy target, too, by default, by perhaps explicitly adding some rule?

Rohit

[Alex Humesky]

Hmm, I'm not sure I understand, could you elaborate? Normally if you're doing "bazel build mypackage:Test", you would just change that to "bazel build mypackage:Test_deploy.jar".

[Rohit Saboo]

When we say bazel build //path:..., the deploy package isn't normally built. Is there something that can be done to have it be built in those cases?

Rohit

[Alex Humesky]

I'm not aware of a clean way to do this. I would usually just refer to exactly what I want to build, since I would eventually need to refer to them explicitly in bazel-bin anyway.

Can you elaborate on your general use case? For example, if you have many different java_binary rules you want to build the deploy jar from as a part of a release process, you can do something like

$ bazel query "kind(java_binary, java/...)"

which will give all the labels for all the java_binary rules under the java package. Then you can add "_deploy.jar" to those and build them explicitly. E.g.:

$ bazel query "kind(java_binary, java/...)" | sed 's/$/_deploy.jar/' | xargs bazel build

You'd still need to find them in bazel-bin (maybe you use the results of the query).

[Rohit Saboo]

Hi Alex,

Yep basically needed that for automated processes. This sample command works well.

Thanks,

Rohit

Rohit

[Alex Humesky]

Great, glad that helps.

Thinking more about this, we could potentially add an output group in bazel for deploy jars, then you could do something like "bazel build //package/... --output_groups=+deploy_jars" (you can, for example, do "--output_groups=+_source_jars" to get all the source jars for java rules). You'd still have the problem of finding them in bazel-bin, so you'd probably end up doing a bazel query anyway. You can make a request for this at https://github.com/bazelbuild/bazel/issues if you would like.