Gradle: Automatic and IDE-independent redeployments on OpenLiberty

25 February 2018

The last weeks I have started to experiment how well VSCode can be used for Java EE development. I have to say that it is quiet exciting to watch what the guys at Microsoft and Red Hat are doing with the Java integration. The gist of it: It cannot replace a real Java IDE yet for a majority of heavy development, but i can see the potential due to its lightweightness in projects that also involve a JavaScript frontend. The experience of developing Java and JavaScript in this editor is quiet nice compared to a beast like Eclipse.

One of my first goals for quick development: Reproduce the automatical redeploy you get from IDEs like Eclipse (via JBoss Tools). I.e. changing a Java-class automatically triggers a redeploy of the application. As long as you make sure the WAR-file is small, this deploy task takes less then a second and allows for quick iterations.

Here the steps how to make this work in VS Code; actually, they are independent of VSCode and just leverage Gradle’s continous-build feature.

Place this task in your build.gradle. It deploys your application to the dropins-folder of OpenLiberty if you have set up the environment variable wlpProfileHome.

task deployToWlp(type: Copy, dependsOn: 'war') {
    dependsOn 'build'
    from war.archivePath
    into "${System.env.wlpProfileHome}/dropins"
}

Additionally, make sure to enable automatic redeploys in your server.xml whenever the contents of the dropins-folder change.

<!-- hot-deploy for dropins -->
<applicationMonitor updateTrigger="polled" pollingRate="500ms" dropins="dropins" dropinsEnabled="true"/>

Every time you run gradlew deployToWlp, this should trigger a redeploy of the latest code.

Now comes the next step: Run gradlew deployToWlp -t for continuous builds. Every code-change should trigger a redeploy. This is indepdent of any IDE and thus works nicely together with VS Code in case you want this level of interactivity. If not, it is very easy to just map a shortcut to the gradle-command in VSCode to trigger it manually.