[oe] meta-java: adding support for gradle build tool and gradle based recipes

[Andrea Galbusera]

Hello,

I'd like to estimate the feasibility of bringing some java libraries
and tools to the embedded platforms that I manage with variants of
oe/yocto stacks.
I looked around and noticed a meta-java layer is available: I hope
this is the right place to ask about it, since I found no
layer-specific list. If I'm off topic here, please suggest more
suitable pointers.

Said java libs and tools require gradle [1] to build. My guess is that
a native recipe for gradle will be needed first. This appear to be a
"ant-like" problem, since gradle is said to be using gradle itself to
build.
I had a look at it's build documentation and source code. There is a
shell script setting up suitable parameters for JVM, then downloading
a wrapper class which builds the tool from sources.

Before going for experimentations...
1. Did anybody already try to set up a recipe for gradle?
2. What are the expected challenges I'm supposed to meet in setting up
a native java based recipe leveraging meta-java? Is there any
particular limitation in current native environment used i.e for
building ant?
3. Could it be a reasonable approach to temporarily use a host build
of gradle as a jump start for building final libs and tools? If so,
what will be the required setup to instruct other recipes for using
the host version of gradle. I know this is evil, but I expect more
trouble in building gradle than gradle based recipes. Of course, this
might be a completely wrong perception! ;-)

Hope the java masters will forgive me if my questions sound silly. I'm
not a "building-for-java" expert at all: I hope this could be an
opportunity to learn something new!

[1] http://www.gradle.org

Regards,
Andrea