每个线程一个“Java上下文”？

Question

Is it possible to launch a Java program from another Java program, just as if I were launching it using another Java command? When calling the main() method of a program from another program directly, the Java context is common to these both executions. I'm trying to have one Java context per thread.

Illustration:

src/com/project/ProjectLauncher.java

public class ProjectLauncher {

    static {
        PropertyConfigurator.configure("log4j.properties");
    }

    public static void main(String[] args) {
        Logger.getLogger(ProjectLauncher.class).info("started!");
        // Logs well as expected.
    }

}

test/com/project/TestProject.java

public class TestProject extends TestCase {

    public void testProject() {
        ProjectLauncher.main(null);
        Logger.getLogger(TestProject.class).info("tested!");
        // The above line logs well, while log4j has been initialized in ProjectLauncher.
        // I would like it to need its own initialization in this class.
    }

}

I tried to launch the main method in another thread/runnable, but the logger is still initialized by ProjectLauncher.

Answer 1

Well when you start a Java process, its a new Instance of JVM. If you wish to start another JVM instance, then you need to start a separate process of it.

ie

    List<String> command = new ArrayList<String>();
    command.add("java");
    command.add("ProjectLauncher");
    ProcessBuilder builder = new ProcessBuilder(command);
    builder.redirectErrorStream(true);
    final Process process = builder.start();
        try {
           process.waitFor();
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        }
        //if you wish to read the output of it then below code else you can omit it.
        InputStream is = process.getErrorStream();
        InputStreamReader isr = new InputStreamReader(is);
        BufferedReader br = new BufferedReader(isr);
        String line;
        while ((line = br.readLine()) != null) {
            Logger.getLogger(MyClass.class.getName()).severe(line);
        }

Above we are ultimately starting a new process which in reality is java ProjectLauncher . In case if the class is not already compiled, then you will have to compile it similar to above but using javac instead of java and ProjectLauncher.java instead of ProjectLauncher etc.