摘要：類提供了執(zhí)行從進(jìn)程輸入執(zhí)行輸出到進(jìn)程等待進(jìn)程完成檢查進(jìn)程的退出狀態(tài)以及銷毀殺掉進(jìn)程的方法。解決進(jìn)程無限阻塞的方法是在執(zhí)行命令時(shí)，設(shè)置一個(gè)超時(shí)時(shí)間，下面提供一個(gè)工具類，對(duì)使用進(jìn)行包裝，向外提供設(shè)置超時(shí)的接口。

在前一篇博文中，簡(jiǎn)單介紹了如何使用Process類來調(diào)用命令行的功能，那樣使用Process會(huì)有一個(gè)很大的問題，就是可能會(huì)出現(xiàn)無限阻塞的情況，永遠(yuǎn)都無法返回結(jié)果。以下是Process的API說明，注意加粗的部分。

  
ProcessBuilder.start() 和 Runtime.exec 方法創(chuàng)建一個(gè)本機(jī)進(jìn)程，并返回 Process 子類的一個(gè)實(shí)例，該實(shí)例可用來控制進(jìn)程并獲得相關(guān)信息。Process 類提供了執(zhí)行從進(jìn)程輸入、執(zhí)行輸出到進(jìn)程、等待進(jìn)程完成、檢查進(jìn)程的退出狀態(tài)以及銷毀（殺掉）進(jìn)程的方法。

  創(chuàng)建進(jìn)程的方法可能無法針對(duì)某些本機(jī)平臺(tái)上的特定進(jìn)程很好地工作，比如，本機(jī)窗口進(jìn)程，守護(hù)進(jìn)程，Microsoft Windows 上的 Win16/DOS 進(jìn)程，或者 shell 腳本。創(chuàng)建的子進(jìn)程沒有自己的終端或控制臺(tái)。它的所有標(biāo)準(zhǔn) io（即 stdin、stdout 和 stderr）操作都將通過三個(gè)流 (getOutputStream()、getInputStream() 和 getErrorStream()) 重定向到父進(jìn)程。父進(jìn)程使用這些流來提供到子進(jìn)程的輸入和獲得從子進(jìn)程的輸出。因?yàn)橛行┍緳C(jī)平臺(tái)僅針對(duì)標(biāo)準(zhǔn)輸入和輸出流提供有限的緩沖區(qū)大小，如果讀寫子進(jìn)程的輸出流或輸入流迅速出現(xiàn)失敗，則可能導(dǎo)致子進(jìn)程阻塞，甚至產(chǎn)生死鎖。

解決進(jìn)程無限阻塞的方法是在執(zhí)行命令時(shí)，設(shè)置一個(gè)超時(shí)時(shí)間，下面提供一個(gè)工具類，對(duì)Process使用進(jìn)行包裝，向外提供設(shè)置超時(shí)的接口。

ExecuteResult類，對(duì)執(zhí)行命令的結(jié)果進(jìn)行封裝，可以從中獲取退出碼和輸出內(nèi)容。

public class ExecuteResult {
    @Override
    public String toString() {
        return "ExecuteResult [exitCode=" + exitCode + ", executeOut="
                + executeOut + "]";
    }

    private int exitCode;
    private String executeOut;

    public ExecuteResult(int exitCode, String executeOut) {
        super();
        this.exitCode = exitCode;
        this.executeOut = executeOut;
    }

    public int getExitCode() {
        return exitCode;
    }

    public void setExitCode(int exitCode) {
        this.exitCode = exitCode;
    }

    public String getExecuteOut() {
        return executeOut;
    }

    public void setExecuteOut(String executeOut) {
        this.executeOut = executeOut;
    }

}

LocalCommandExecutorService 接口，向外暴露executeCommand（）方法

public interface LocalCommandExecutorService {
    ExecuteResult executeCommand(String[] command, long timeout);
}

LocalCommandExecutorServiceImpl 實(shí)現(xiàn)類，實(shí)現(xiàn)LocalCommandExecutorService 接口的方法

public class LocalCommandExecutorServiceImpl implements
        LocalCommandExecutorService {
    static final Logger logger = LoggerFactory
            .getLogger(LocalCommandExecutorServiceImpl.class);

    static ExecutorService pool = new ThreadPoolExecutor(0, Integer.MAX_VALUE,
            3L, TimeUnit.SECONDS,
            new SynchronousQueue());

    @Override
    public ExecuteResult executeCommand(String[] command, long timeout) {
        Process process = null;
        InputStream pIn = null;
        InputStream pErr = null;
        StreamGobbler outputGobbler = null;
        StreamGobbler errorGobbler = null;
        Future executeFuture = null;
        try {
            process = Runtime.getRuntime().exec(command);
            final Process p = process;

            //close process"s output stream.
            p.getOutputStream().close();

            pIn = process.getInputStream();
            outputGobbler = new StreamGobbler(
                    pIn, "OUTPUT");
            outputGobbler.start();

            pErr = process.getErrorStream();
            errorGobbler = new StreamGobbler(pErr, "ERROR");
            errorGobbler.start();

            // create a Callable for the command"s Process which can be called
            // by an Executor
            Callable call = new Callable() {
                public Integer call() throws Exception {
                    p.waitFor();
                    return p.exitValue();
                }
            };

            // submit the command"s call and get the result from a
            executeFuture = pool.submit(call);
            int exitCode = executeFuture.get(timeout,
                    TimeUnit.MILLISECONDS);
            return new ExecuteResult(exitCode, outputGobbler.getContent());
        } catch (IOException ex) {
            String errorMessage = "The command [" + command
                    + "] execute failed.";
            logger.error(errorMessage, ex);
            return new ExecuteResult(-1, null);
        } catch (TimeoutException ex) {
            String errorMessage = "The command [" + command + "] timed out.";
            logger.error(errorMessage, ex);
            return new ExecuteResult(-1, null);
        } catch (ExecutionException ex) {
            String errorMessage = "The command [" + command
                    + "] did not complete due to an execution error.";
            logger.error(errorMessage, ex);
            return new ExecuteResult(-1, null);
        } catch (InterruptedException ex) {
            String errorMessage = "The command [" + command
                    + "] did not complete due to an interrupted error.";
            logger.error(errorMessage, ex);
            return new ExecuteResult(-1, null);
        } finally {
            if(executeFuture != null){
                try{
                executeFuture.cancel(true);
                } catch(Exception ignore){}
            }
            if(pIn != null) {
                this.closeQuietly(pIn);
                if(outputGobbler != null && !outputGobbler.isInterrupted()){
                    outputGobbler.interrupt();
                }
            }
            if(pErr != null) {
                this.closeQuietly(pErr);
                if(errorGobbler != null && !errorGobbler.isInterrupted()){
                    errorGobbler.interrupt();
                }
            }
            if (process != null) {
                process.destroy();
            }
        }
    }

      private void closeQuietly(Closeable c) {
        try {
            if (c != null)
                c.close();
        } catch (IOException e) {
        }
    }
}

StreamGobbler類，用來包裝輸入輸出流

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class StreamGobbler extends Thread {
    private static Logger logger = LoggerFactory.getLogger(StreamGobbler.class);
    private InputStream inputStream;
    private String streamType;
    private StringBuilder buf;
    private volatile boolean isStopped = false;

    /**
     * Constructor.
     * 
     * @param inputStream
     *            the InputStream to be consumed
     * @param streamType
     *            the stream type (should be OUTPUT or ERROR)
     * @param displayStreamOutput
     *            whether or not to display the output of the stream being
     *            consumed
     */
    public StreamGobbler(final InputStream inputStream, final String streamType) {
        this.inputStream = inputStream;
        this.streamType = streamType;
        this.buf = new StringBuilder();
        this.isStopped = false;
    }

    /**
     * Consumes the output from the input stream and displays the lines
     * consumed if configured to do so.
     */
    @Override
    public void run() {
        try {
            //默認(rèn)編碼為UTF-8，這里設(shè)置編碼為GBK，因?yàn)閃IN7的編碼為GBK
            InputStreamReader inputStreamReader = new InputStreamReader(
                    inputStream,"GBK");
            BufferedReader bufferedReader = new BufferedReader(
                    inputStreamReader);
            String line = null;
            while ((line = bufferedReader.readLine()) != null) {
                this.buf.append(line + "
");
            }
        } catch (IOException ex) {
            logger.trace("Failed to successfully consume and display the input stream of type "
                            + streamType + ".", ex);
        } finally {
            this.isStopped = true;
            synchronized (this) {
                notify();
            }
        }
    }

    public String getContent() {
        if(!this.isStopped){
            synchronized (this) {
                try {
                    wait();
                } catch (InterruptedException ignore) {
                }
            }
        }
        return this.buf.toString();
    }
}

測(cè)試用例

public class LocalCommandExecutorTest {
    public static void main(String[] args) {
        LocalCommandExecutorService service = new LocalCommandExecutorServiceImpl();
        String[] command = new String[]{"ping","127.0.0.1"};
        ExecuteResult result = service.executeCommand(command, 5000);
        System.out.println("退出碼："+result.getExitCode());
        System.out.println("輸出內(nèi)容："+result.getExecuteOut());     
    }
}

輸出結(jié)果如下：

直接在命令行執(zhí)行“ping 127.0.0.1”，結(jié)果如下：

  
Apache提供了一個(gè)開源庫(kù)，對(duì)Process類進(jìn)行了封裝，也提供了設(shè)置超時(shí)的功能，建議在項(xiàng)目中使用Apache Commons Exec這個(gè)開源庫(kù)來實(shí)現(xiàn)超時(shí)功能，除了功能更強(qiáng)大外，穩(wěn)定性也有保障。