我使用 Runtime exec() 方法在 Java 中创建一个子进程。但是,由于子进程是一个交互式程序,我需要在它需要时向它提供输入。我还需要显示子流程的输出。我怎样才能以最简单的方式做到这一点?
我使用 StreamGobbler 来显示使用 process.getInputStream() 的程序输出。但是,我不知道如何识别程序何时等待输入以及何时使用 proc.getOutputStream 为其提供输入。我该怎么做?
最佳答案
您需要在子进程的流和 System
流之间复制输入和输出(System.in
、System.out
和 System.err
)。这与 my recent quesion 有关.到目前为止我找到的最佳解决方案是:
import java.io.FileInputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Field;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousCloseException;
import java.nio.channels.FileChannel;
class StreamCopier implements Runnable {
private InputStream in;
private OutputStream out;
public StreamCopier(InputStream in, OutputStream out) {
this.in = in;
this.out = out;
}
public void run() {
try {
int n;
byte[] buffer = new byte[4096];
while ((n = in.read(buffer)) != -1) {
out.write(buffer, 0, n);
out.flush();
}
}
catch (IOException e) {
System.out.println(e);
}
}
}
class InputCopier implements Runnable {
private FileChannel in;
private OutputStream out;
public InputCopier(FileChannel in, OutputStream out) {
this.in = in;
this.out = out;
}
public void run() {
try {
int n;
ByteBuffer buffer = ByteBuffer.allocate(4096);
while ((n = in.read(buffer)) != -1) {
out.write(buffer.array(), 0, n);
out.flush();
}
out.close();
}
catch (AsynchronousCloseException e) {}
catch (IOException e) {
System.out.println(e);
}
}
}
public class Test {
private static FileChannel getChannel(InputStream in)
throws NoSuchFieldException, IllegalAccessException {
Field f = FilterInputStream.class.getDeclaredField("in");
f.setAccessible(true);
while (in instanceof FilterInputStream)
in = (InputStream)f.get((FilterInputStream)in);
return ((FileInputStream)in).getChannel();
}
public static void main(String[] args)
throws IOException, InterruptedException,
NoSuchFieldException, IllegalAccessException {
Process process = Runtime.getRuntime().exec("sh -i +m");
Thread outThread = new Thread(new StreamCopier(
process.getInputStream(), System.out));
outThread.start();
Thread errThread = new Thread(new StreamCopier(
process.getErrorStream(), System.err));
errThread.start();
Thread inThread = new Thread(new InputCopier(
getChannel(System.in), process.getOutputStream()));
inThread.start();
process.waitFor();
System.in.close();
outThread.join();
errThread.join();
inThread.join();
}
}
这里棘手的部分是从 System.in
中提取一个 channel 。否则,您将无法在子进程终止时中断读取输入的线程。
这种方法有一个严重的缺点:关闭 System.in
后,您将无法再从中读取。我目前使用的解决方法是让一个输入重定向线程用于所有子进程。
关于java - 运行子进程,在 Java 中正确地为其提供输入和输出,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/4272956/