Executing a Java Application in a Separate Process

Executing a Java application in a separate process

Two hints:

System.getProperty("java.home") + "/bin/java" gives you a path to the java executable.

((URLClassLoader) Thread.currentThread().getContextClassLoader()).getURL() helps you to reconstruct the classpath of current application.

Then your EXECUTE.application is just (pseudocode):

Process.exec(javaExecutable, "-classpath", urls.join(":"), CLASS_TO_BE_EXECUTED)

Whether JVM runs in User Process or Separate Process

1. JVM is running inside a process that was started by executing java.exe/javaw.exe on Windows or the java executable for Unix/GNU. Its owner would be the one that runs the executable. If two java programs are running then two JVMs in different processes will be created.

2. GC is a thread inside the JVM, see here

For example, the Java garbage collector is a daemon thread.

Java starting another Java Application

Near dupe Java execute process on linux and Difference between ProcessBuilder and Runtime.exec()

In addition to the correct points about tilde-(non-)expansion, you are passing an entire commandline as one argument to new ProcesssBuilder. Unlike Runtime.exec() which treats a single String as a special case and splits into whitespace-delimited tokens mostly (but not exactly) like typical Unix shells, the ProcessBuilder ctor does not do this. This can be seen in the exception message at the beginning of the traceback you posted. You need separate arguments like:

ProcessBuilder builder = new ProcessBuilder("java", "-jar", 
    System.getProperty("user.home")+"/Documents.Java/myJar.jar");
// three String's passed to vararg, compiler makes array for you

or possibly (but I don't recommend)

String line = "java -jar " + System.getProperty("user.home")+"/Documents.Java/myJar.jar";
ProcessBuilder builder = new ProcessBuilder( line.split(" ") );
// array of three String's passed directly to vararg

And replace java by a full pathname if the desired java program (or a link to it) isn't found first when searching the PATH in effect for your JVM process.

Running java as a separate process in windows command line through uDeploy

Try using Deamon option https://developer.ibm.com/urbancode/plugindoc/ibmucd/shell/1-2/steps/, this will run in the background and will not hold your current step for long

run class file as separate process from java code

The java command expects a Java class name, not a filename.

So the command java E:/workspace/JNIProgram/src/JNIProgram.class is wrong. If you try this manually from a command prompt window you'll get an error message.

The command should be something like this:

java -cp E:\workspace\JNIProgram\src JNIProgram

Note: What's after the -cp option is the classpath, and after that the fully-qualified class name (which is just JNIProgram, if the class is not in a package).

First make sure that you can run the command manually from the command line before you make it work from another Java program.

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