java-如何使用带有参数的exitValue()？

一篇很好的文章(当Runtime.exec()不会)说：您唯一可能使用exitValue()而不是waitFor()的时间是当您不希望您的程序阻塞在某个外部进程上等待时,可能永远不会完成.与其使用waitFor()方法,不如将一个名为waitFor的布尔参数传递给exitValue()方法,以确定当前线程是否应等待.布尔值会更有益,因为exitValue()是此方法的更合适的名称,并且两个方法不必在不同的条件下执行相同的功能.这种简单的条件判别是输入参数的领域.

我的情况完全相同,我的系统调用将启动一个进程,该进程将一直运行,直到用户决定杀死它为止.如果我使用'(process.waitFor()== 0)’,它将在此阻止程序,因为进程将无法完成.以上文章的作者建议exitValue()可以与“ waitFor”参数一起使用.有人尝试过吗？任何示例都将有所帮助.

码：

//启动ProcessBuilder,“ str”包含命令

ProcessBuilder pbuilder = new ProcessBuilder(str);
pbuilder.directory(new File("/root/workspace/Project1"));
pbuilder.redirectErrorStream(true);
Process prcs = pbuilder.start();
AForm.execStatustext.append("\n=> Process is:" + prcs);

// Read output
StringBuilder out = new StringBuilder();
BufferedReader bfrd = new BufferedReader(new InputStreamReader(process.getInputStream()));
String current_line = null, previous_line = null;
while ((current_line = bfrd.readLine()) != null) {
    if (!line.equals(previous_line)) {
        previous_line = current_line;
        out.append(current_line).append('\n');
        //System.out.println(line);
    }
}
//process.getInputStream().close();
// Send 'Enter' keystroke through BufferedWriter to get control back
BufferedWriter bfrout = new BufferedWriter(new OutputStreamWriter(prcs.getOutputStream()));
bfrout.write("\\r");
bfrout.newLine();
bfrout.flush();
bfrout.write("\\r");
bfrout.newLine();
bfrout.flush();
//process.getOutputStream().close();*/

if (prcs.waitFor() == 0)
    System.out.println("Commands executed successfully");
System.exit(0); 

解决方法:

在主线程中使用waitFor之前,请创建另一个线程(子代),并在此新线程中为终止情况构造逻辑.例如,等待10秒.
如果满足条件,则从子线程ant中断主线程,并在主线程上处理以下逻辑.

以下代码创建一个子线程来调用该进程,主线程执行其工作,直到子进程成功完成.

    import java.io.IOException;


    public class TestExecution {

        public boolean myProcessState = false;

        class MyProcess implements Runnable {

            public void run() {
                //------
                Process process;
                try {
                    process = Runtime.getRuntime().exec("your command");
                    process.waitFor();
                    int processExitValue = process.exitValue();

                    if(processExitValue == 0) {
                        myProcessState = true;
                    }

                } catch (IOException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }

        }

        public void doMyWork() {

            MyProcess myProcess = new MyProcess();

            Thread myProcessExecuter = new Thread(myProcess);
            myProcessExecuter.start();

            while(!myProcessState) {
                // do your job until the process exits with success
            }
        }

        public static void main(String[] args) {

            TestExecution testExecution = new TestExecution();
            testExecution.doMyWork();
        }
    }

标签：processbuilder,java,nonblocking
来源： https://codeday.me/bug/20191009/1882749.html