Building a maven war overlay project with gradle

Question

I want to integrate a maven project into my gradle build process. Although I was successful in converting the maven project (which is a war overlay project) into a gradle project, there are several drawbacks doing this. First of all the maven tomcat plugin can easily create a runnable jar with an embedded tomcat instance. I could not find a gradle plugin which does this job. To solve the problem I see four different approaches, I wonder which one would be the best or if there is another possibility.

1. Convert maven project to gradle. As mentioned before this works, but I could not find a way to create a jar with embedded tomcat with this approach.
2. The maven project will have an additional build.gradle which has tasks to execute the maven goals (for example ant.exec)
3. I use maven for all my projects (not really an option for me)
4. Use maven as root project and execute gradle tasks from maven

Any other ideas or suggestions?

Answer 1

You could:

1. Create a java application using tomcat embedded
2. Use the gradle shadow plugin to create an executable über jar for the java application

Answer 2

After investigating some time, I want to answer the question by myself. I think converting the maven project to a gradle project in this special case isn't the best approach. I decided to use the second approach:

The war-overlay project is still a maven project but I also add a gradle.build file to the project. The build script looks like this:

task mvnPackage(type:Exec) {
    commandLine "${mavenHome}/mvn", 'package'
}

task mvnClean(type: Exec) {
    commandLine "${mavenHome}/mvn", 'clean'
}

clean.dependsOn mvnClean

assemble.dependsOn mvnPackage

So if I use gradle as build tool, maven goals will be executed, which works perfectly.

Answer 3

I'm not sure how reliable this is but you can also instantiate and execute some maven mojos without needing the maven container/harness (details here)

I'm not sure if this is possible with the maven tomcat mojo.