Why doesn't the Java console show when using ProcessBuilder?

问题

I use the following to launch a Java application from another Java app.

    ProcessBuilder pb = new ProcessBuilder(javaPath + javaCommand, maxMemStr,
            minMemStr, stackSizeStr, jarCommand, jarfile, jarArg);
    try {
        Process p = pb.start();
    } catch (IOException ex) {
        Logger.getLogger(launch.class.getName()).log(Level.SEVERE, null, ex);
    }

where javaCommand is either java or javaw (javaPath is empty most of the time unless a user points to an alternate path). The problem is, after the app launches, even when I verify the process list to contain java, it doesn't show the console.

Is it because PrcoessBuilder doesn't invoke the command shell? Is there a way to show the console programatically?

Thanks in advance.

回答1:

This is because the "command console" itself is a process that attaches to the std-in/-out/-err streams of another process and displays them on the screen. When you launch Java all by itself, no other processes will be handling those streams, hence the lack of a command console. To get the results you want, you will need to launch a new instance of the command console and subsequently have it run your custom java command.

There may be a better way to do this... but I think the solution to this is going to be platform-dependent. In Windows, you could do something like:

ProcessBuilder pb = new ProcessBuilder("start", "\"JAwesomeSauce\"", "cmd.exe",
    "/k", javaPath + javaCommand, maxMemStr, minMemStr, stackSizeStr, jarCommand,
    jarfile, jarArg);
try {
    Process p = pb.start();
} catch (IOException ex) {
    Logger.getLogger(launch.class.getName()).log(Level.SEVERE, null, ex);
}

I assume you could do something similar in Linux/Mac if that's the O/S you're using.

回答2:

You may want to run the command like this: cmd /K java ... or cmd /C java ...

回答3:

As far as I remember the Processbuilder opens a pipe to a specific process.

Your command window is a process itself with all you see. If you enter commands the cmd/bash usually creates new processes and attaches to them.

来源：https://stackoverflow.com/questions/14466201/why-doesnt-the-java-console-show-when-using-processbuilder

标签

java

console

processbuilder