Creating an RPM for a Java Application
Creating an RPM for a Java Application
Herein lays an example of creating an RPM for Java Applications with Gradle.
Overview
Creating a RPM that can run a Java application requires two steps. The first is to create a jar file that can be ran. The second is to create a RPM that installs this jar file and its dependecies on the target system. This certainly isn’t the only way to do this, but it seems to be the easiest.
Creating a runnable JAR file
There are many resources out there for creating a runnable JAR file. The Gradle application plugin will even create a jar for you out of the box. A regular JAR file isn’t enough, you need a JAR file that also contains all of it dependecies. This kind of Jar file is often called a fat or uber JAR because of these extra dependecies. Luckly for us, a gradle plugin called Shadow takes care of this.
You can add shadow to your gradle file by adding the following lines to the beginning of your *.gradle file:
plugins {
id 'com.github.johnrengelman.shadow' version '2.0.1'
}
Assuming you have the rest of your gradle set up to run your java application, you can immediately use Shadow after adding this line. Shadow adds a few gradle tasks, the one we are interested in is gradle shadowJar. See gradle tasks for all the exposed tasks shadow introduces.
Try it out. Run gradle shadowJar and look in your build/libs folder for the newly generated JAR file. you can run this jar file with java -jar somefile.jar.
Creating an RPM package
To create an RPM package I used the ospackage gradle plugin. The plugin can be added to your gradle file by editing the plugins field we added in the last section. Modify it to look like:
plugins {
id "nebula.ospackage" version "4.4.2"
id 'com.github.johnrengelman.shadow' version '2.0.1'
}
Unlike the shadow plugin, ospackage requires the user to apply this plugin. I did so by adding the following line:
apply plugin: "nebula.ospackage"
ospackage doesn’t know how to create an RPM specific to your project, it requires some extra configuration. See the RPM packaging guide for information on how to configure it. Give it your best shot, here Is what I came up with:
ospackage {
release '1.el7'
user 'foo'
permissionGroup "foo"
summary 'Testing that RPMs can be created and ran using Java.'
arch 'X86_64'
os 'LINUX'
type 'BINARY'
from (shadowJar.outputs.files) {
into "/opt/test"
}
from("scripts/rpmtest") {
into "/opt/test"
fileMode = 0755
}
}
buildRpm {
requires("some-dep", "0.2.7", GREATER | EQUAL)
directory("/opt/test", 0755)
link("/usr/bin/rpmtest", "/opt/test/rpmtest")
}
buildRpm.dependsOn(shadowJar)
There are a few things to point out in my configuration. First buildRpm.dependsOn(shadowJar). This is required so you can copy the JAR that shadow creates into your RPM. Second, I had to create a script to acutally run my fat JAR. This script is really simple, it just runs:
#!/usr/bin/env sh
java -jar /opt/test/rpmtest-*
After I finished this configuration I tested this approach by installing the rpm and attempting to run it. After a few permissions tweaks and trial and error, I got it running with the solution above.