Java-Runtime.exec（）无法运行

Question

When i try to run any Runtime.exec() command like this simple one to print the java version:

String [] cmd = { "java", "-version" };
Runtime runtime = Runtime.getRuntime();
Process process = runtime.exec(cmd);

BufferedReader stdError = new BufferedReader( new InputStreamReader( process.getErrorStream() ) );
String s = null;

while ( ( s = stdError.readLine() ) != null )
    System.out.println(s);

It works just fine, but if i am using a JRE bundled with my Java application i always get errors saying that java is unknown:

java.io.IOException: Cannot run program "java": error=2, No such file or directory
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)
    at java.lang.Runtime.exec(Runtime.java:620)
    at java.lang.Runtime.exec(Runtime.java:450)
    at java.lang.Runtime.exec(Runtime.java:347)
    at org.runner.Runner.main(Runner.java:11)

Why does this happen when using a bundled JRE?

Answer 1

After a lot of investigation i was able to fix this. I will add my working solution here, may be it will help someone having the same issue:

This issue is caused due to this reported JDK bug: https://bugs.java.com/view_bug.do?bug_id=5049299

And since i have this issue on Mac OS X, it was safe for me to use "fork" instead of "posix_spawn" by setting the Java System property:

if( isMacOSX() ) System.setProperty( "jdk.lang.Process.launchMechanism", "FORK" );

This might be a discouraged solution, but it has really fixed a huge problem for me on Mac OS X.

Answer 2

I ran into this problem on MacOS too. It only affected my application when using my bundled jre. While switching to 'fork' (as you did in your answer) worked for me. I was curious that there must be a 'better' solution since the bug report you pointed to was filed and fixed years ago. So after a little more digging, I found that, on MacOS there is a executable in the bundled jre (../jre/Contents/Home/jre/lib/jspawnhelper) that needs to be executable in order for Runtime.exec() to work. It was not, but as soon as I made it executable my processes ran without error.

To make it executable, I added this to the build.properties file in feature that bundles the jre:

root.macosx.cocoa.x86_64.permissions.755=jre/Contents/Home/jre/lib/*

You may need to make adjustments to that line depending on you arch and jre location.

Answer 3

Make sure java is added to PATH environment variable. If it is not, use absolute path of the executable. For eg:

String [] cmd = { "//usr//bin//java", "-version" };

Answer 4

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class PP {

    public void pop(){
    String [] cmd = { "java", "-version" };
    Runtime runtime = Runtime.getRuntime();
    Process process = null;
    try {
        process = runtime.exec(cmd);
    } catch (IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    BufferedReader stdError = new BufferedReader( new InputStreamReader( process.getErrorStream() ) );
    String s = null;

    try {
        while ( ( s = stdError.readLine() ) != null )
            System.out.println(s);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    }
        public static void main(String []args){
            PP pp=new PP();
        pp.pop();
        }

}