Question

我必须将数据从fragment传递到json任务然后传递给servlet。我已经包含了fragment，class和servlet的代码。

public class Home extends Fragment {

    public Home() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        ListView lvAccountSummary;

        Bundle bundle = getActivity().getIntent().getExtras();
        String userId = bundle.getString("userName");
        Toast.makeText(getActivity().getApplicationContext(),userId,Toast.LENGTH_SHORT).show();
        View view = inflater.inflate(R.layout.fragment_home,container,false);
        lvAccountSummary = (ListView) view.findViewById(R.id.lvAccountSummary);
        new JSONTask(view.getContext(), lvAccountSummary).execute("http://localhost:8080/examples/examplesSummary");
        return view;
    }

}

这是以下JSON任务，它从servlet获取数据并显示在片段

上

public class JSONTask extends AsyncTask<String,String,List<SummaryModel>> {
     private ListView lvSummary;
     private Context mContext;
     private ProgressDialog dialog;
     public JSONTask(Context context, ListView  lstView){
        this.lvSummary = lstView;
        this.mContext = context;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        dialog = new ProgressDialog(mContext);
        dialog.setIndeterminate(true);
        dialog.setCancelable(false);
        dialog.setMessage("Loading. Please wait...");
        dialog.show();
    }

    @Override
    protected List<SummaryModel> doInBackground(String... params) {
        HttpURLConnection connection = null;
        BufferedReader reader = null;
        try {
            URL url= new URL(params[0]);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");
            connection.connect();
            InputStream stream = connection.getInputStream();
            reader = new BufferedReader(new InputStreamReader(stream));
            StringBuffer buffer = new StringBuffer();
            String line ="";
            while ((line = reader.readLine())!=null){
                buffer.append(line);
            }
            String finalJason = buffer.toString();

            JSONObject parentObject = new JSONObject(finalJason);
            JSONArray parentArray = parentObject.getJSONArray("account");

            List<SummaryModel> accountModelList = new ArrayList<>();

            Gson gson = new Gson();

            for (int i=0; i<parentArray.length();i++) {
                JSONObject finalObject = parentArray.getJSONObject(i);
                SummaryModel summaryModel = gson.fromJson(finalObject.toString(),SummaryModel.class);
                accountModelList.add(summaryModel);
            }
            return  accountModelList;

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    @Override
    protected void onPostExecute(List<SummaryModel> result) {
        super.onPostExecute(result);
        dialog.dismiss();
        AccountAdapter adapter = new AccountAdapter(mContext,R.layout.row,result);
        try {
            lvSummary.setAdapter(adapter);
        } catch (Exception e){
            Toast.makeText(mContext,"No Internet Connection",Toast.LENGTH_SHORT).show();
        }
            //TODO need to set data to the list
    }
}

但是当我从servlet调用userId时，我得到空值

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    //String userName;
    System.out.println("++++++++++++++++++++"+(String)request.getParameter("userId"));
    ...
}

Answer 1

您没有在请求中传递user_id，因此您的Servlet中没有得到user_id。请尝试以下代码：

    @Override
        protected List<SummaryModel> doInBackground(String... params) {

Map<String,Object> params = new LinkedHashMap<>();
        params.put("userId", "12");


        StringBuilder postData = new StringBuilder();
        for (Map.Entry<String,Object> param : params.entrySet()) {
            if (postData.length() != 0) postData.append('&');
            postData.append(URLEncoder.encode(param.getKey(), "UTF-8"));
            postData.append('=');
            postData.append(URLEncoder.encode(String.valueOf(param.getValue()), "UTF-8"));
        }
        byte[] postDataBytes = postData.toString().getBytes("UTF-8");


            HttpURLConnection connection = null;



            BufferedReader reader = null;
            try {
                URL url= new URL(params[0]);
                connection = (HttpURLConnection) url.openConnection();
                connection.setRequestMethod("POST");
                connection.setRequestProperty("Content-Length",         String.valueOf(postDataBytes.length));
        connection.setDoOutput(true);
        connection.getOutputStream().write(postDataBytes);
                connection.connect();
                InputStream stream = connection.getInputStream();
                reader = new BufferedReader(new InputStreamReader(stream));
                StringBuffer buffer = new StringBuffer();
                String line ="";
                while ((line = reader.readLine())!=null){
                    buffer.append(line);
                }
                String finalJason = buffer.toString();

                JSONObject parentObject = new JSONObject(finalJason);
                JSONArray parentArray = parentObject.getJSONArray("account");

                List<SummaryModel> accountModelList = new ArrayList<>();

                Gson gson = new Gson();

                for (int i=0; i<parentArray.length();i++) {
                    JSONObject finalObject = parentArray.getJSONObject(i);
                    SummaryModel summaryModel = gson.fromJson(finalObject.toString(),SummaryModel.class);
                    accountModelList.add(summaryModel);
                }
                return  accountModelList;

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            } finally {
                if (connection != null) {
                    connection.disconnect();
                }
                try {
                    if (reader != null) {
                        reader.close();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return null;
        }

将数据从片段传递到servlet

1 个答案: