从服务器接收响应时出错？

Posted 2023-05-07

【中文标题】从服务器接收响应时出错？

【英文标题】：Error receiving response from the server?

【发布时间】：2018-02-04 11:01:01

【问题描述】：

我正在制作一个将一些数据存储在数据库中的应用程序，然后它会检索它。 在服务器端我使用 php，在客户端我有这个文件，它获取输入并将其传递给 PHP 文件。

new AsyncTask<String, String, String>() 

                JSONParser jsonParser = new JSONParser();
                private ProgressBar pBar;
                private String url_post_pet = "http://192.168.0.13/android/post_pet.php";

                // JSON Node names
                private static final String TAG_SUCCESS = "success";

                /**
                 * Before starting background thread Show Progress Dialog
                 */
                @Override
                protected void onPreExecute() 
                    super.onPreExecute();
                    //pBar = new ProgressBar();
                    //pBar.setIndeterminate(false);
                    //pBar.setVisibility(View.VISIBLE);
                

                @Override
                protected String doInBackground(String... args) 
                    // Building Parameters
                    HashMap<String, String> params = new HashMap<>();
                    params.put("name", a);
                    params.put("breed", BREED);
                    params.put("type", TYPE);
                    params.put("images", "Whatever");
                    params.put("description", c);
                    params.put("coords", b);

                    // getting JSON Object
                    // Note that create product url accepts POST method
                    JSONObject json = jsonParser.makeHttpRequest(url_post_pet,
                            "POST", params);
                    // check log cat for response
                    Log.d("Create Response", json.toString());

                    // check for success tag
                    try 
                        int success = json.getInt(TAG_SUCCESS);

                        if (success == 1) 
                            // successfully created product
                            Intent i = new Intent(getApplicationContext(), MainActivity.class);
                            startActivity(i);

                            // closing this screen
                            finish();
                         else 
                            // failed to create product
                        
                     catch (JSONException e) 
                        System.out.println("exception" + e);
                        e.printStackTrace();
                    
                    System.out.println("nul");
                    return null;
                

                /**
                 * After completing background task Dismiss the progress dialog
                 **/
                protected void onPostExecute(String file_url) 
                    // dismiss the dialog once done
                    //pBar.dismiss();
                
            .execute();

        
    );

另外，我有这个 JSONParser：

public class JSONParser 

String charset = "UTF-8";
HttpURLConnection conn;
DataOutputStream wr;
StringBuilder result;
URL urlObj;
JSONObject jObj = null;
StringBuilder sbParams;
String paramsString;

public JSONObject makeHttpRequest(String url, String method,
                                  HashMap<String, String> params) 

    sbParams = new StringBuilder();
    int i = 0;
    for (String key : params.keySet()) 
        try 
            if (i != 0)
                sbParams.append("&");
            
            sbParams.append(key).append("=")
                    .append(URLEncoder.encode(params.get(key), charset));

         catch (UnsupportedEncodingException e) 
            e.printStackTrace();
        
        i++;
    

    if (method.equals("POST")) 
        // request method is POST
        try 
            urlObj = new URL(url);
            conn = (HttpURLConnection) urlObj.openConnection();
            conn.setDoOutput(true);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Accept-Charset", charset);
            conn.setReadTimeout(10000);
            conn.setConnectTimeout(15000);
            conn.connect();

            paramsString = sbParams.toString();

            wr = new DataOutputStream(conn.getOutputStream());
            wr.writeBytes(paramsString);
            wr.flush();
            wr.close();

         catch (IOException e) 
            e.printStackTrace();
        
    
    else if(method.equals("GET"))
        // request method is GET

        if (sbParams.length() != 0) 
            url += "?" + sbParams.toString();
        

        try 
            urlObj = new URL(url);
            conn = (HttpURLConnection) urlObj.openConnection();
            conn.setDoOutput(false);
            conn.setRequestMethod("GET");
            conn.setRequestProperty("Accept-Charset", charset);
            conn.setConnectTimeout(15000);
            conn.connect();

         catch (IOException e) 
            e.printStackTrace();
        

    

    try 
        //Receive the response from the server
        InputStream in = new BufferedInputStream(conn.getInputStream());
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        result = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) 
            result.append(line);
        

        Log.d("JSON Parser", "result: " + result.toString());
     catch (IOException e) 
        e.printStackTrace();
    

    conn.disconnect();

    // try parse the string to a JSON object
    try 
        System.out.println(jObj);
        jObj = new JSONObject(result.toString());
     catch (JSONException e) 
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    

    // return JSON Object
    return jObj;

这是我每次提交数据时遇到的错误：

08-26 12:51:08.236 5089-5156/chtecnologies.myapplication D/JSON 解析器：结果：08-26 12:51:08.239 5089-5156/chtecnologies.myapplication E/JSON 解析器：解析数据组织时出错。 json.JSONException：输入在字符 0 处结束 08-26 12:51:08.793 5089-5096/chtecnologies.myapplication W/艺术：暂停所有线程占用：190.496ms 08-26 12:51:09.245 5089-5096/chtecnologies.myapplication W/艺术：暂停所有线程占用：137.277ms 08-26 12:51:09.267 5089-5156/chtecnologies.myapplication E/AndroidRuntime: 致命异常: AsyncTask #1 进程：chtecnologies.myapplication，PID：5089 java.lang.RuntimeException：执行 doInBackground() 时发生错误 在 android.os.AsyncTask$3.done(AsyncTask.java:304) 在 java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355) 在 java.util.concurrent.FutureTask.setException(FutureTask.java:222) 在 java.util.concurrent.FutureTask.run(FutureTask.java:242) 在 android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 在 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 在 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 在 java.lang.Thread.run(Thread.java:818) 原因：java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法“java.lang.String org.json.JSONObject.toString()” 在 chtecnologies.myapplication.PostPet$4$1.doInBackground(PostPet.java:154) 在 chtecnologies.myapplication.PostPet$4$1.doInBackground(PostPet.java:118) 在 android.os.AsyncTask$2.call(AsyncTask.java:292) 在 java.util.concurrent.FutureTask.run(FutureTask.java:237) 在 android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 在 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 在 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 在 java.lang.Thread.run(Thread.java:818)

数据成功进入数据库，但JSONParser似乎有问题，无法得到PHP文件的结果。

如果 JSONParser 文件或其他地方有什么问题，您能告诉我吗？这是我第一次在我的应用程序中实现服务器，希望你能帮助我！谢谢

【参考方案1】：

您发送数据的方式看起来很可疑。如果您想在 POST 中发送数据，请使用 HttpURLConnection 之类的

String postParam = "name=" + a + "&breed=" + BREED + "&type=" + "&images=" +
        Whatever + "&description=" + c + "&coords=" + b;

try 
    URL url = new URL(url);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();

    connection.setRequestMethod("POST");
    connection.setDoOutput(true);
    connection.setDoInput(true);
    connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded");

    OutputStream os = connection.getOutputStream();
    os.write(postParam.getBytes());
    os.flush();
    os.close();

    // Fetching the response code
    responseCode = connection.getResponseCode();
    Log.d(TAG, "POST Response Code: " + responseCode);
 catch (Exception e) 
    e.printStackTrace();

connection.setRequestMethod- 设置您希望使用 GET/POST 发送数据的方法

connection.setDoOutput(true)- 让你发送输出

connection.setDoInput(true)- 让您在发送数据后接收输入（如果有）

希望这能解决您的问题！