How to deploy/host java spark app for example on AWS?

Edvards.

This may be coming very late, but here it goes. I can't speak towards AWS, but Spark has an embedded web-server called Jetty in order to host. Your application will simply have to include all of your dependencies (the .jar files that Gradle pulled in for you) in the class path. Once you launch your packaged .jar (using command: java -jar app.jar), the embedded Jetty server just starts up. Alternatively, there's a concept called "super jar" or "fat jar" where you can write a task for Gradle to incorporate all of your dependencies into a single .jar file so that you don't ever have to worry about class path and so you can just build and run the .jar file wherever you want your web-server to be without having to worry about an actual web-server with appropriate extensions installed locally (again, thanks to embedded Jetty).

here is a sample Gradle task i found for a fat jar you can add to your project's build.gradle file:

task fatJar(type: Jar) {
    manifest {
        attributes 'Implementation-Title': 'Gradle Jar File Example',
                'Implementation-Version': version,
                'Main-Class': 'com.teamtreehouse.courses.Main'
    }
    baseName = project.name + '-all'
    from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }
    with jar
}

If you don't want to use Jetty, Spark can also be deployed into a Tomcat environment. I don't know if TreeHouse will allow a reference to a third-party site, but here's a tutorial that can help you. About half-way down the page there is information on deploying Spark to Tomcat. link

Good luck. Spark is Awesome!!!