Runtime.getRuntime().exec執行阻塞問題解決

上篇博文中CallMaxentThreadPoolTask類直接使用Runtime.getRuntime().exec方法調用cmd命令，結果今天在測試時發現當cmd命令執

 

行出現錯誤或警告時，主控程序的waitfor方法會被阻塞一直等待下去，查了查資料發現是Runtime.getRuntime().exec方法須要本身處理

 

stderr 及stdout流，而解決方法便是將它們導出用別的thread處理。

 

會形成阻塞的代碼：

 

Process p = Runtime.getRuntime().exec(cmd);

p.waitFor();

 

解決方法：

Process p = Runtime.getRuntime().exec(cmd);

StreamGobbler errorGobbler = new StreamGobbler(p.getErrorStream(), "ERROR");

      // kick off stderr
      errorGobbler.start();

      StreamGobbler outGobbler = new StreamGobbler(p.getInputStream(), "STDOUT");
      // kick off stdout
      outGobbler.start();

p.waitFor();

 

其中StreamGobbler類的代碼：

 

package com.sdc.callmaxent.socket;

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

import com.sdc.callmaxent.util.FileUtil;

/**
 * 用於處理Runtime.getRuntime().exec產生的錯誤流及輸出流
 * @author shaojing
 *
 */
public class StreamGobbler extends Thread {
    InputStream is;
    String type;
    OutputStream os;

    StreamGobbler(InputStream is, String type) {
        this(is, type, null);
    }

    StreamGobbler(InputStream is, String type, OutputStream redirect) {
        this.is = is;
        this.type = type;
        this.os = redirect;
    }

    public void run() {
        InputStreamReader isr = null;
        BufferedReader br = null;
        PrintWriter pw = null;
        try {
            if (os != null)
                pw = new PrintWriter(os);

            isr = new InputStreamReader(is);
            br = new BufferedReader(isr);
            String line=null;
            while ( (line = br.readLine()) != null) {
                if (pw != null)
                    pw.println(line);
                System.out.println(type + ">" + line);
            }

            if (pw != null)
                pw.flush();
        } catch (IOException ioe) {
            ioe.printStackTrace();
        } finally{
            FileUtil.close(pw);
            FileUtil.close(br);
            FileUtil.close(isr);
        }
    }
}

 

感謝http://faq.csdn.net/read/200584.html中提到的各位。