How to build Spring Boot multimodule app build to separate WARs and shared library/dependencies?

Currently i’am trying to migrate multimodule angular + spring 4 app build with ant and ivy to Spring Boot and build it with Gradle. Issue is that i don’t how to create build upon some custom requirements.
Currently app consist 10 separate modules, each module is built to WAR file and deployed on standalone tomcat. Modules communicate with soap and there is one “public module” with common classes etc. which is build to jar and distributed with ant to all modules as library.
What do i have to achieve with Gradle:
a) Create multimodule structure with parrent file which will aggregate common dependencies for all modules, but every module should be build to separate WAR file and should be able to build separatelly or all app at once.
b) Create one common module which will contain common classes and propagate them into modules as libraries or dependencies. I was thinking maybe about something like repository or something else which aggregate dependecies so there is no need to distribute classes as jar?
Problem is that i read big part of documentation but still don’t know where to begin upon this requirements. It would be great if you guys at least give a hint which topic should i consider.

We decided to not use any migration tools for ant, goal is to get rid of it completely.