code: public StringBuffer readFile(String filename) throws IOException {
  		BufferedReader reader = new BufferedReader(new FileReader(filename));
  		StringBuffer xml = new StringBuffer();
  		String line = null;
          while((line = reader.readLine()) != null){
              xml.append(line);
          }
  		reader.close();
  		return xml;
  	}
docs: 逐行读取文件内容
  
  @param filename 文件名
  
  @return 文件内容
  
  @throws IOException 文件读取异常