Java线程题——监听n个错误流

Question

首先让我说一下，我在线程方面的经验很低。

我有一个应用程序可以通过 Runtime.exec 方法启动其他几个 Java jar。问题是启动的 jar 需要同时运行，但是为了获得启动的 jar 的错误流，您基本上必须有一个循环“坐着听”，直到过程完成。

这是我现在拥有的:

_processes.add( Runtime.getRuntime().exec( commandList.toArray( new String[ commandList.size() ] ) ) );
Thread thread = new Thread( new Runnable() {
    private final int _processNumber = _processes.size() - 1;
    public void run() {
        String streamData = _processNumber + " : ";
        streamData += "StdError [\r";
        BufferedReader bufferedReader =
                new BufferedReader( new InputStreamReader( _processes.get( _processNumber ).getErrorStream() ) );
        String line = null;
        try {
            while ( ( line = bufferedReader.readLine() ) != null ) {
                streamData += line + "\r";
            }
            bufferedReader.close();
            streamData += "]\r";
            LOG.error( streamData );
        }
        catch ( Exception exception ) {
            LOG.fatal( exception.getMessage() );
            exception.printStackTrace();
        }
    }
} );
thread.start();

谁能解释如何让“错误流监听器线程”正常工作？

TIA

Answer 1

不使用 Runtime.getRuntime().exec()，而是使用 Process启动外部流程。这会让您的生活变得更加轻松。

我的项目中的示例代码:

    //Build command 
    List<String> commands = new ArrayList<String>();
    commands.add("my_application");
    commands.add("arg1");
    commands.add("arg2");
    log.debug("{}", commands);

    //Run command with arguments
    ProcessBuilder pb = new ProcessBuilder(commands);
    pb.directory(directory);
    pb.redirectErrorStream(true);
    Process process = pb.start();

    //Read output
    StringBuilder out = new StringBuilder();
    BufferedReader br = new BufferedReader(new InputStreamReader
        (process.getInputStream()));

    //Only log unique lines (you might not need this)
    String line = null, previous = null;
    while ((line = br.readLine()) != null)
        if (!line.equals(previous)) {
            previous = line;
            out.append(line).append('\n');
            log.debug(line);
        }

    //Check result
    if (process.waitFor() == 0)
        return 0;

    //Abnormal termination: Log command parameters and output and throw ExecutionException
    log.error("{}", commands);
    log.error("\n{}", out.toString());
    throw new ExecutionException(new IllegalStateException("MyApplication exit code 1"));