如何在使用 HttpURLConnection (android/java) 发布之前获取 VIEWSTATE？

Question

我正在编写一个 Android 应用程序，并且一直在寻找一种从我要发布到的服务器中获取 _VIEWSTATE 的方法，以便我可以将其放入我的 Http 发布内容中。一些人推荐了正则表达式，但其他一些专业人士强烈反对使用正则表达式解析 HTML。那么，如何解析 _VIEWSTATE 呢？我在 AsyncTask 中使用 HttpURLConnection/HttpsURLConnection。另外，我不需要把 InputStream 阅读器放在首位，才能先获得 _VIEWSTATE 吗？所有的 android 示例都将输入流放在输出流之后。到目前为止，这是我的代码的样子（发布到一个必须“点击通过”的三个页面的网站）：

在我的活动中，我这样调用异步任务：

//execute AsyncTask for all three reports
    submit_report.execute(report1, report2, report3); 

我的异步任务 doInBackground 方法：

class UploadReportTask extends AsyncTask<HashMap<String,String>, ProgressBar, Void> {

//this is called on task.execute
    protected Void doInBackground(HashMap<String,String>...maps) {
        System.out.println("Report is being uploaded"); 

        URL url = null;
        try {
            url = new URL(getString(R.string.url_dnc));
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
        HttpURLConnection urlConnection = null;
        try {
            urlConnection = (HttpURLConnection) url.openConnection();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            urlConnection.setDoOutput(true);
            urlConnection.setRequestProperty("Accept-Charset", utf);
            urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded;charset=" + utf);
            urlConnection.setChunkedStreamingMode(0);


            //For each map in maps, encode the map,
            //get the headers, add the headers to the map, convert to bytes,
            //then post the bytes, 
            //get response.
            for (HashMap<String,String> map : maps){
                byte[] payload = makePayload(map);
                OutputStream out = new BufferedOutputStream(urlConnection.getOutputStream());
                //urlConn.connect //I think this happens here
                out.write(payload);

                InputStream in = new BufferedInputStream(urlConnection.getInputStream());

                BufferedReader reader = new BufferedReader(new InputStreamReader(in));
                int length = in.read();
                String result, line = reader.readLine();
                result = line;
                while (length != -1){
                    result+=line;
                }
                System.out.println(result);
                out.flush();
                out.close();
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
        finally{
            urlConnection.disconnect();
        }
        return null;    
    }

Answer 1

protected String parseViewstate(String response){
        int i = 0;
        String viewstate = "";
        while (true){
            int found = response.indexOf("\"__VIEWSTATE\"", i);
            if (found == -1) break;
            int start = found + 38; //check numbers from start of "__V"
            int end  = (response.indexOf("/>", start)) -2;
            viewstate = response.substring(start, end);
            i = end + 1;    
        }return viewstate;
    }