java ASYNCTASK中的HttpUrlConnection && parseJSON

Posted 2021-05-08

//data store
    private void parseJSON(String result) {
        ArrayList<HashMap<String, String>> loadData = new ArrayList<>();

        try {
            JSONArray jsonArray = new JSONArray(result);

            for (int i = 0; i < jsonArray.length(); i++) {

                HashMap<String, String> loadDataMap = new HashMap<>();

                JSONObject jsonObject = jsonArray.getJSONObject(i);

                loadDataMap.put("exh_uid", jsonObject.getString("exh_uid"));
                loadDataMap.put("app_uid", jsonObject.getString("app_uid"));

                loadData.add(loadDataMap);
            }

            myGlobalValue.setLoadData(loadData);
        } catch (JSONException e) {
            e.printStackTrace();
        }

    }

private ArrayList<HashMap<String, String>> loadData = new ArrayList<>();

    public void setLoadData(ArrayList<HashMap<String, String>> loadData) {
        this.loadData = loadData;
    }

    public ArrayList<HashMap<String, String>> getLoadData() {
        return loadData;
    }

//INNER CLASS
class JobTask2 extends AsyncTask<String, Void, String> {

        //
        HttpURLConnection urlConnection = null;

        @Override
        protected String doInBackground(String... params) {
            HttpURLConnection urlConnection = null;

            try {
                URL url = new URL("http://drupal.udn-device-dept.net/Exhibition/api/getSpecificData.php");
                urlConnection = (HttpURLConnection) url.openConnection();
                //setRequestMethod:set the method for the URL request.
                urlConnection.setRequestMethod("POST");

                //Read the response.
                //The response body may be read from the stream returned by getInputStream().
                urlConnection.setDoInput(true);
                //Instances must be configured with setDoOutput(true) if they include a request body.
                urlConnection.setDoOutput(true);

                //POST method cannot save data to caches, so it need to set usecaches metohod to false.
                urlConnection.setUseCaches(false);
//                urlConnection.setChunkedStreamingMode(0);
                urlConnection.setRequestProperty("Content-Type", "application/json");
                urlConnection.connect();

                //Create JSONObject here
                JSONObject usuario = new JSONObject();
                usuario.put("app_uid", "automatic");
                usuario.put("get_enroll", "yes");

                // Send POST output.
                OutputStreamWriter out = new OutputStreamWriter(urlConnection.getOutputStream());
                out.write(usuario.toString());
                out.flush();
                out.close();

                //check urlconnection with response code 200(OK).
                int status = urlConnection.getResponseCode();
                if (status == HttpURLConnection.HTTP_OK) {
                    //post request variables.
                    InputStream is = urlConnection.getInputStream();
                    StringBuilder response = new StringBuilder();
                    BufferedReader reader = new BufferedReader(new InputStreamReader(is));
                    String line;

                    while ((line = reader.readLine()) != null) {
                        response.append(line + "\r");
                    }
                    reader.close();
                    return response.toString();
                }
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException j) {
                Log.d(TAG, "doInBackground: json");
            } finally {
                //cut the connection.
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
            }

            return null;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            parseJSON(s);

            info.setText(s);

            //take the {key,value} from getloaddata method and return to store in hashmap.
            for (HashMap<String, String> a : myGlobalValue.getLoadData()) {
                //store data to list array.
                /*List<HashMap<String, String>> test = new ArrayList<>();
                test.add(a);
                String b = test.toString();*/

                info.setText(a.get("app_uid").toString() + "\n" + a.get("exh_uid").toString() + "\n" + a.values());

                System.gc();
            }
        }

    }

## HttpUrlConnection  
  
###### Android高效入門-解析JSON資料,使用json.org、Gson、Jackson教學
(https://litotom.com/2016/05/26/android6-json-gson-jackson/)
  
#### 簡述  
  
Android中发送http网络请求是很常见的，要有GET请求和POST请求。  
一个完整的http请求需要经历两个过程：客户端发送请求到服务器，然后服务器将结果返回给客户端。  
  
![](http://img.blog.csdn.net/20160516215923341)  
  
#### HttpClient的一般使用步驟:
  
1.使用DefaultHttpClient類型實做HttpClient物件  
  
2.創建HttpGet或HttpPost物件,將請求的URL通過建構的方法傳入HttpGet或HttpPost物件  
  
3.調用execute方法發送HTTP GET或HTTP POST請求,並回傳給HttpResponse物件  
  
4.通過HttpResponse接口的getEntity方法取得伺服器回應的訊息,並進行相應的處理  
  
最後記得在AndroidManifest.xml文件添加網路權限  
<uses-permission android:name="android.permission.INTERNET" />  

#### GET、POST方式的差別:  
  
GET请求可以被缓存。POST请求从不会被缓存。  
  
1.GET是從伺服器上取得數據,POST是向伺服器傳送數據  
  
2.在客戶端,GET方式在通過URL提交數據,數據在URL中可以看到,POST方式數據放在HTML HEADER內提交  
  
3.對於GET方式,伺服器端用Request.QueryString獲取變數的值(值會出現在request header裡)
  對於POST方式,伺服器用Request.Form獲取提交的數據(值會在Response Body裡,較具安全性)    
  
4.GET方式提交的數據大於2KB(主要是URL長度限制),而POST則沒有此限制  
  
5.安全性問題,正如差別2.提到,使用GET的時候,參數會顯示在地址欄上,而POST不會,所以如果這些是中文數據而且是非敏感數據,那麼使用GET
如果用戶輸入的數據不是中文字元而且包含敏感數據,那麼還是使用POST數據為好。  
  

    //inner class
    class JobTask1 extends AsyncTask<String, Void, String> {

        @Override
        protected String doInBackground(String... params) {

//          HttpURLConnection & BufferedReader need to declared outside the try/catch.
            HttpURLConnection urlConnection = null;
            BufferedReader reader = null;

//          Will contain the raw JSON response as a String.
            String jsonstr = null;

            //
            try {
                //Construct the URL for the backend query.
                URL url = new URL("https://video.udn.com/api-cowork/com-app");

                //Create the request to backend, and open the connection.
                urlConnection = (HttpURLConnection) url.openConnection();
                urlConnection.setRequestMethod("GET");
                urlConnection.connect();

                //Read the input Stream into a string.
                InputStream inputStream = urlConnection.getInputStream();
                StringBuffer buffer = new StringBuffer();
                if (inputStream == null) {
                    return null;
                }
                reader = new BufferedReader(new InputStreamReader(inputStream));

                String line;
                while ((line = reader.readLine()) != null) {
                    buffer.append(line + "\n");
                }

                if (buffer.length() == 0) {
                    return null;
                }
                jsonstr = buffer.toString();
            } catch (MalformedURLException e) {
                Log.d(TAG, "doInBackground: ", e);
            } catch (IOException i) {
                Log.d(TAG, "doInBackground: ", i);
            } finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
            return jsonstr;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            info.setText(s);
            Log.i(TAG, "onPostExecute: ");
        }
    }