我使用Runtime exec()方法在
Java中创建子进程.但是,由于子进程是一个交互式程序,我需要在需要时为它提供输入.另外,我需要显示子进程的输出.我怎样才能以最简单的方式做到这一点？
我使用StreamGobbler使用process.getInputStream()显示程序输出.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提供输入.我怎样才能做到这一点？
解决方法
您需要复制子进程的流和系统流(System.in,System.out和System.err)之间的输入和输出.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,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(),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中提取一个通道.如果没有这个,你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之后,你再也无法读取它了.我目前使用的解决方法是使用单个输入重定向线程用于所有子进程.
