Cloud Foundry, run-task, simple HelloWorld.java

Question

i just want to have a simple Application like Hello World run as a Task on CloudFoundry.

So i want to cf run-task myapp firstArgument secondArgument

Is it possible to deploy an app on Cloud Foundry and start this jar like on a linux Console.

java -jar simpleApp.jar firstargument seconArgument 

Answer 1

Yes, that is 100% possible.

1. Build your application & compile it.
2. Package it into a JAR file that can be executed. Test & confirm locally by running java -jar your-app.jar .
3. Now cf push -p path/to/youar-app.jar your application. The Java buildpack should detect the app & install the software required to run the app.
4. The Java buildpack & CloudFoundry in general expect the app that you push to start & run forever. If your application does not, if it's meant to start and only run for a finite period of time, the app is going to fail to start but that's OK. You can ignore that. After it fails, run cf stop .
5. If you have a task that runs for a finite period of time, you need one additional step. Run cf run-task <your-app> <arg1> <arg2> ... . The trick is that Java will not be on the $PATH so you need to use the full path to the Java executable, which is .java-buildpack/open_jdk_jre/bin/java . For example, if you wanted to print the Java version, cf run-task your-cool-app ".java-buildpack/open_jdk_jre/bin/java -version" (make sure you have the command quoted, escape quotes within the command accordingly).

See this SO post for more background on running tasks: https://stackoverflow.com/a/67872218/1585136