在Android應用程序中使用寧靜的服務

我有我自己的寧靜網頁應用程序（spring引導），它產生JSON數據，我想獲取JSON數據並在我的android應用程序中顯示它。但是我得到一個NullPointerException和JsonMappingException。任何幫助，將不勝感激。在Android應用程序中使用寧靜的服務

Web應用程序控制器：

@RestController 
@RequestMapping("/") 
public class IndexController { 
    private ProductService productService; 

    @Autowired 
    public void setProductService(ProductService productService) { 
     this.productService = productService; 
    } 

    @RequestMapping(method = RequestMethod.GET , produces = MediaType.APPLICATION_JSON_VALUE) 
    public Iterable<Product> getAllProducts(){ 

     return productService.listAllProducts(); 


    } 

}

JSON數據通過Web應用程序產生的（它的推移和回覆111通過流API獲取微博）：

[{"productId":758916869776478208,"description":"LYS Türkiye 688’si ve 857.si Ömer Özyer’den Fethiye’nin Altın Kızları #haber #sondakika @habermatik aracılığıyla","name":"erkanilik48","location":"fethiye gazetesi sahibi"},{"productId":758916869961101316,"description":"I'm at Balıkesir in Balıkesir, Türkiye","name":"onplaka","location":"Bursa-Balıkesır"},{"productId":758917112295362560,"description":"Erdoğan'sız Türkiye diyorlar anket yaptım bakalım ahali nasıl Türkiye istiyor anket süresi 10 dakika .","name":"TakipGalaxi","location":"New York , LITTLE ITALY"},{"productId":758917117353668610,"description":"RT @TATARKENAN23: AğlarkenSeni Türkiye ye götüreceğiz denildiğinde susan çocuklar varHalep için DÛA bekliyoruz","name":"NecmeddinLd","location":null}]

Android應用MainActivity：

@Override 
    protected void onStart() { 
     super.onStart(); 
     new HttpRequestTask().execute(); 


    } 


    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.menu_main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     //noinspection SimplifiableIfStatement 
     if (id == R.id.action_settings) { 
      return true; 
     } 

     if (id == R.id.action_refresh) { 
      new HttpRequestTask().execute(); 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 


    private class HttpRequestTask extends AsyncTask<Void, Void, Greeting> { 
     @Override 
     protected Greeting doInBackground(Void... params) { 
      try { 
       final String url = "blabla"; 
       RestTemplate restTemplate = new RestTemplate(); 
       restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter()); 
       Greeting greeting; 
       greeting = restTemplate.getForObject(url, Greeting.class); 
       return greeting; 
      } catch (Exception e) { 
       Log.e("MainActivity", e.getMessage(), e); 
      } 

      return null; 
     } 

     @Override 
     protected void onPostExecute(Greeting greeting) { 
      TextView text1 = (TextView) findViewById(R.id.textView); 
      TextView text2 = (TextView) findViewById(R.id.textView2); 
      TextView text3 = (TextView) findViewById(R.id.textView3); 
      TextView text4 = (TextView) findViewById(R.id.textView4); 

      assert text1 != null; 
      text1.setText((int) greeting.getProductId()); 
      assert text2 != null; 
      text2.setText(greeting.getDescription()); 
      assert text3 != null; 
      text3.setText(greeting.getName()); 
      assert text4 != null; 
      text4.setText(greeting.getLocation()); 


     } 

    } 
}

CONSOLE LOG：

                 [ 07-29 06:50:00.665 2886: 2932 D/   ] 
                      HostConnection::get() New Host Connection established 0xae552980, tid 2932 
    07-29 06:50:00.706 2886-2932/org.hello.tweetconsumer I/OpenGLRenderer: 

Initialized EGL, version 1.4 
07-29 06:50:00.740 2886-2932/org.hello.tweetconsumer W/EGL_emulation: eglSurfaceAttrib not implemented 
07-29 06:50:00.740 2886-2932/org.hello.tweetconsumer W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xaaac9420, error=EGL_SUCCESS 
07-29 06:50:02.663 2886-2931/org.hello.tweetconsumer E/MainActivity: Could not read JSON: Can not deserialize instance of org.hello.tweetconsumer.Greeting out of START_ARRAY token 
                     at [Source: buffer([email protected]43f53).inputStream(); line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of org.hello.tweetconsumer.Greeting out of START_ARRAY token 
                     at [Source: buffer([email protected]43f53).inputStream(); line: 1, column: 1] 
                    org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Can not deserialize instance of org.hello.tweetconsumer.Greeting out of START_ARRAY token 
                     at [Source: buffer([email protected]43f53).inputStream(); line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of org.hello.tweetconsumer.Greeting out of START_ARRAY token 
                     at [Source: buffer([email protected]43f53).inputStream(); line: 1, column: 1] 
                     at org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.readInternal(MappingJackson2HttpMessageConverter.java:126) 
                     at org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:147) 
                     at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:76) 
                     at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:484) 
                     at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:439) 
                     at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:237) 
                     at org.hello.tweetconsumer.MainActivity$HttpRequestTask.doInBackground(MainActivity.java:90) 
                     at org.hello.tweetconsumer.MainActivity$HttpRequestTask.doInBackground(MainActivity.java:82) 
                     at android.os.AsyncTask$2.call(AsyncTask.java:295) 
                     at java.util.concurrent.FutureTask.run(FutureTask.java:237) 
                     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234) 
                     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113) 
                     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588) 
                     at java.lang.Thread.run(Thread.java:818) 
                     Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of org.hello.tweetconsumer.Greeting out of START_ARRAY token 
                     at [Source: buffer([email protected]43f53).inputStream(); line: 1, column: 1] 
                     at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:691) 
                     at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:685) 
                     at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromArray(BeanDeserializerBase.java:1215) 
                     at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:151) 
                     at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:126) 
                     at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2993) 
                     at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2158) 
                     at org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.readInternal(MappingJackson2HttpMessageConverter.java:123) 
                      ... 13 more 
07-29 06:50:02.664 2886-2886/org.hello.tweetconsumer D/AndroidRuntime: Shutting down VM 


                     --------- beginning of crash 
07-29 06:50:02.665 2886-2886/org.hello.tweetconsumer E/AndroidRuntime: FATAL EXCEPTION: main 
                     Process: org.hello.tweetconsumer, PID: 2886 
                     java.lang.NullPointerException: Attempt to invoke virtual method 'long org.hello.tweetconsumer.Greeting.getProductId()' on a null object reference 
                      at org.hello.tweetconsumer.MainActivity$HttpRequestTask.onPostExecute(MainActivity.java:107) 
                      at org.hello.tweetconsumer.MainActivity$HttpRequestTask.onPostExecute(MainActivity.java:82) 
                      at android.os.AsyncTask.finish(AsyncTask.java:651) 
                      at android.os.AsyncTask.-wrap1(AsyncTask.java) 
                      at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668) 
                      at android.os.Handler.dispatchMessage(Handler.java:102) 
                      at android.os.Looper.loop(Looper.java:148) 
                      at android.app.ActivityThread.main(ActivityThread.java:5417) 
                      at java.lang.reflect.Method.invoke(Native Method) 
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

來源

2016-07-29 Didem

檢查您創建的模型以反序列化您的JSON，並確保您的屬性名稱遵循Camel-Case中的Oracle文檔，除此之外，您還需要明確提及它們作爲@Seralizedname in m奧德爾。我假設你正在使用某種GSON解串器。 –

你在期待什麼？問候或可迭代？您不能將Iterable 映射爲Greeting實體。 – Celtik

真的我會改變， – Didem

如果您的意圖是將Iterable映射爲Greeting，那麼您希望收集Greetings而不是唯一的Greeting。

所以你要替換此：

Greeting

通過這樣的：

Greeting[]

你的代碼應該是這樣的：

private class HttpRequestTask extends AsyncTask<Void, Void, Greeting[]> { 
    @Override 
    protected Greeting[] doInBackground(Void... params) { 
     try { 
      final String url = "blabla"; 
      RestTemplate restTemplate = new RestTemplate(); 
      restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter()); 
      Greeting[] greeting; 
      greeting = restTemplate.getForObject(url, Greeting[].class); 
      return greeting; 
     } catch (Exception e) { 
      Log.e("MainActivity", e.getMessage(), e); 
     } 

     return null; 
    } 

    @Override 
    protected void onPostExecute(Greeting[] greeting) { 
     TextView text1 = (TextView) findViewById(R.id.textView); 
     TextView text2 = (TextView) findViewById(R.id.textView2); 
     TextView text3 = (TextView) findViewById(R.id.textView3); 
     TextView text4 = (TextView) findViewById(R.id.textView4); 

     assert text1 != null; 
     text1.setText((int) greeting[0].getProductId()); 
     assert text2 != null; 
     text2.setText(greeting[0].getDescription()); 
     assert text3 != null; 
     text3.setText(greeting[0].getName()); 
     assert text4 != null; 
     text4.setText(greeting[0].getLocation()); 


    } 

}

另外，儘量改變返回ResponseEntity提供的服務類型如下：

@RequestMapping(method = RequestMethod.GET , produces = MediaType.APPLICATION_JSON_VALUE) 
public ResponseEntity<Iterable<Product>> getAllProducts(){ 

    return new ResponseEntity<Iterable<Product>>(productService.listAllProducts(), HttpStatus.OK); 
}

來源

2016-07-29 07:32:23 Celtik

做到了這一點，但仍然無法讀取JSON數據也許它是因爲我的控制器返回Iterable – Didem

它是否返回相同的消息異常？ – Celtik

檢查您的日誌後，似乎API在異步任務中的postExecute上返回null對象。

@Override 
    protected void onPostExecute(Greeting greeting) { 

    if(greeting != null) { 

     TextView text1 = (TextView) findViewById(R.id.textView); 
     TextView text2 = (TextView) findViewById(R.id.textView2); 
     TextView text3 = (TextView) findViewById(R.id.textView3); 
     TextView text4 = (TextView) findViewById(R.id.textView4); 

     assert text1 != null; 
     text1.setText((int) greeting.getProductId()); 
     assert text2 != null; 
     text2.setText(greeting.getDescription()); 
     assert text3 != null; 
     text3.setText(greeting.getName()); 
     assert text4 != null; 
     text4.setText(greeting.getLocation()); 
     } else { 
     // Show logs or Toast 
    } 

    }

以下鏈接幫助關於JsonMappingException希望你：

JSON: JsonMappingException while try to deserialize object with null values

來源

2016-07-29 07:41:16

我改變了問候語來問候[]，使我的返回類型List<Product>，而不是Iterable<Product>，現在它的工作thnks所有

來源

2016-07-29 08:12:03 Didem

在Android應用程序中使用寧靜的服務

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