String InputStream 转换

//String2InputStream
private InputStream String2InputStream(String str){
        ByteArrayInputStream stream = new ByteArrayInputStream(str.getBytes());
        return stream;
    }

//inputStream2String
private String inputStream2String(InputStream is){
        BufferedReader in = new BufferedReader(new InputStreamReader(is));
        StringBuffer buffer = new StringBuffer();
        String line = "";
        try {
            while ((line = in.readLine()) != null){
              buffer.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return buffer.toString();
    }