Java web开发调用外部 ffmpeg或mencoder转码...
遇到的问题是ffmpeg或mencoder进程阻塞, 需要停掉tomcat--javaw.exe进程之后才能执行ffmpeg.exe或mencoder.exe
 
问题的原因: getErrorStream 和 getInputStream 缓冲区没有清空
 
解决的方法: 同时清空getErrorStream 和 getInputStream  的缓冲区
 
代码如下:
      ProcessBuilder builder =  new ProcessBuilder(); 
      builder.command(commend); 
      Process process = builder.start(); 
       final InputStream is1 = process.getInputStream(); 
       new Thread( new Runnable() { 
              public  void run() { 
                     BufferedReader br =  new BufferedReader( new InputStreamReader(is1));    
             try { 
               while(br.readLine() !=  null) ; 
            }  catch (IOException e) { 
              e.printStackTrace(); 
            } 
             } 
      }).start();  // 启动单独的线程来清空process.getInputStream()的缓冲区 
      InputStream is2 = process.getErrorStream(); 
      BufferedReader br2 =  new BufferedReader( new InputStreamReader(is2));    
      StringBuilder buf =  new StringBuilder();  // 保存输出结果流 
      String line =  null; 
       while((line = br2.readLine()) !=  null) buf.append(line);