在 Java 中使用 ProcessBuilder 将一个进程的输出重定向到另一个进程的输入

Redirecting the output of a process into the input of another process using ProcessBuilder in Java

我有两个由 processBuilders 定义的进程:

ProcessBuilder pb1 = new ProcessBuilder (...)
ProcessBuilder pb2 = new ProcessBuilder (...)

我希望 pb1 的输出成为 pb2 的输入。 我在文档中发现我可以使用 pipe:

从另一个进程读取 pb2 的输入
pb2.redirectInput(Redirect.PIPE);

但是,如何指定我希望此管道从 pb1 的输出中读取?

static ProcessBuilder.Redirect INHERIT Indicates that subprocess I/O source or destination will be the same as those of the current process.

static ProcessBuilder.Redirect PIPE Indicates that subprocess I/O will be connected to the current Java process over a pipe.

所以我认为其中之一不会帮助您将一个进程的输出重定向到 另一个进程的输入。你必须自己实现它。

实施:

public class RedirectStreams {
public RedirectStreams(Process process1, Process process2) {
    final Process tmpProcess1 = process1;
    final Process tmpProcess2 = process2;
    new Thread(new Runnable() {
        @Override
        public void run() {
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(tmpProcess1.getInputStream()));
            BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(tmpProcess2.getOutputStream()));
            String lineToPipe;

            try {

                while ((lineToPipe = bufferedReader.readLine()) != null){
                    System.out.println("Output process1 / Input process2:" + lineToPipe);
                    bufferedWriter.write(lineToPipe + '\n');
                    bufferedWriter.flush();
                }

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

}

这个肯定可以设计的更好 我还没有测试过它是否安全运行,但它确实可以。

用法:

RedirectStreams redirectStreams = new RedirectStreams(process1,process2);

测试:

public class ProcessPipeTest {
@Test public void testPipe(){
    try {

        Process process1 = new ProcessBuilder("/bin/bash").start();
        Process process2 = new ProcessBuilder("/bin/bash").start();

        RedirectStreams redirectStreams = new RedirectStreams(process1,process2);

        
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(process1.getOutputStream()));
        String command = "echo echo echo";
        System.out.println("Input process1: " + command);
        bufferedWriter.write(command + '\n');
        bufferedWriter.close();

        
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(process2.getInputStream()));
        String actualOutput = bufferedReader.readLine();
        System.out.println("Output process2: " + actualOutput);
        assertEquals("echo",actualOutput);

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

输出:

Input process1: echo echo echo

Output process1 / Input process2:echo echo

Output process2: echo

从 JDK 9 开始,您可以像这样使用 startPipeline

ProcessBuilder.startPipeline(
    Arrays.asList(
        new ProcessBuilder(...),
        new ProcessBuilder(...),
        ...
    )
)