RuntimeJava.md

Runtime java

This document describes how to write a valid meta/run.yaml configuration file for running Java application. Please note that you needn't require Java MPM package manually since Capstan will require following package automatically:

- openjdk8-zulu-compact1

Running .class

Following configuration can be used to run a javac-compiled Java application inside OSv:

# meta/run.yaml

runtime: java

config_set:
  hello:
    main: MyClass
    args:
      - Johnny

Where the content of MyClass.java file is:

public class MyClass
{
  public static void main(String[] args)
   {
     System.out.println("Hello:");
     for(String el : args){
       System.out.printf("- %s\n", el);
     }
   }
}

Please note that OSv doesn't really need the .java file, but only the .class file that was produced like this:

$ javac MyClass.java

Example:

$ capstan package compose demo
$ capstan run demo --boot hello
Command line will be set based on --boot parameter
Created instance: demo
Setting cmdline: runscript /run/hello
OSv v0.24-448-g829bf76
eth0: 192.168.122.15
java.so: Starting JVM app using: io/osv/nonisolated/RunNonIsolatedJvmApp
java.so: Setting Java system classloader to NonIsolatingOsvSystemClassLoader
Hello:
- Johnny

Running .jar

Following configuration can be used to run .jar file inside OSv:

# meta/run.yaml

runtime: java

config_set:
  hello:
    main: /MyClass.jar
    args:
      - Johnny

The MyClass.jar was prepared out of the very same MyClass.java file as provided above by using the following set of commands:

$ javac MyClass.java
$ jar cfe MyClass.jar MyClass MyClass.class

Example:

$ capstan package compose demo
$ capstan run demo --boot hello
Command line will be set based on --boot parameter
Created instance: demo
Setting cmdline: runscript /run/hello
OSv v0.24-448-g829bf76
eth0: 192.168.122.15
java.so: Starting JVM app using: io/osv/nonisolated/RunNonIsolatedJvmApp
java.so: Setting Java system classloader to NonIsolatingOsvSystemClassLoader
Hello:
- Johnny