import org.apache.hadoop.mapred.TaskLog.Reader; //导入依赖的package包/类
/**
 * Reads tasklog and returns it as string after trimming it.
 * 
 * @param filter
 *          Task log filter; can be STDOUT, STDERR, SYSLOG, DEBUGOUT, PROFILE
 * @param taskId
 *          The task id for which the log has to collected
 * @param isCleanup
 *          whether the task is a cleanup attempt or not.
 * @return task log as string
 * @throws IOException
 */
public static String readTaskLog(TaskLog.LogName filter,
    org.apache.hadoop.mapred.TaskAttemptID taskId, boolean isCleanup)
    throws IOException {
  // string buffer to store task log
  StringBuffer result = new StringBuffer();
  int res;

  // reads the whole tasklog into inputstream
  InputStream taskLogReader = new TaskLog.Reader(taskId, filter, 0, -1,
      isCleanup);
  // construct string log from inputstream.
  byte[] b = new byte[65536];
  while (true) {
    res = taskLogReader.read(b);
    if (res > 0) {
      result.append(new String(b));
    } else {
      break;
    }
  }
  taskLogReader.close();

  // trim the string and return it
  String str = result.toString();
  str = str.trim();
  return str;
}