Automatic and manual rebuilding of Java packages
You have updated a Java library and you want to test whether the update breaks existing reverse-dependencies? Here are a few tips.
The manual method
ubuntu-dev-tools (reverse-depends -b) and devscripts (build-rdeps) contain two useful tools to find reverse-build-dependencies. Usually reverse-depends -b will give you better results. Alternatively you can also use apt-cache rdepends <package> to find reverse-dependencies and to check if the listed build-dependencies are consistent with the dependencies of the package.
First of all install your new build-dependency that should be tested. Download all source packages with apt source <package> and the required build-dependencies with apt build-dep <package>. Change to the package directory and rebuild the package with debuild -us -uc. Repeat the same steps for all reverse-dependencies.
With cowbuilder: sudo DIST=sid ARCH=amd64 cowbuilder --build <package>.dsc
ratt, rebuild all the things!.
Mass rebuild with AWS or similar services
This is a more sophisticated approach for rebuilding a lot or even all Java packages.
Scripts and more documentation can be found at https://github.com/FauxFaux/debjdk9.