Enable compression on resources in primary jar

[joeljeske]

Springboot forbids compression nested jars/archives, however, it does not (to my knowledge) forbid compression assets in the top-level jar. This rule set does disables all the compression on the final artifact, which can result in much higher archive sizes compared to the same application built in gradle for example.

It would be helpful to only disable compression on jars within the top level jar.

[plaird]

@joeljeske thanks for the report, I believe you are correct that the resource entries in the outer jar can be compressed.

[plaird]

I looked into this, this won't be easy. We are jar'ing up the whole mess in a single jar command in the packaging rule

https://github.com/salesforce/bazel-springboot-rule/blob/master/tools/springboot/springboot_pkg.sh#L181

I don't see an easy way to selectively compress some files and not others. To support Windows #25 , I am starting to wonder if we need to rewrite the packaging rule in Java. If we do that, we could also solve this pretty easily.

[plaird]

As of #72 we are now building the executable jar file using multiple invocations of jar command. This is possible because jar has an "update" option. For #72, we are doing this to insure insertion order is deterministic for classloading reasons. I wonder if this same technique could be used to compress some entries but not others.