code: static public String getStackTrace(Exception e) {
  		ByteArrayOutputStream baos = new ByteArrayOutputStream();
  		PrintStream ps = new PrintStream(baos);
  		e.printStackTrace(ps);
  		ps.flush();
  		try {
  			return baos.toString("UTF-8");
  		} catch (UnsupportedEncodingException ee) {
  			return baos.toString();
  		}
  	}
docs: 将Exception的Stack Trace转为字符串