無法讀取JSON：無法將START_OBJECT令牌的java.lang.String實例反序列化（非常簡單的對象）

我在Android中使用Spring進行POST調用，當上面的錯誤彈出時。我看到所有的答案都是關於這個問題的，但是在他們看來，他們似乎在他們想要轉換爲JSON的對象中有數組或列表。煤礦的很簡單：無法讀取JSON：無法將START_OBJECT令牌的java.lang.String實例反序列化（非常簡單的對象）

public class Detection { 

private String vehicleId; 
private String historyDate; 
private double lat; 
private double lon; 
private double speed; 
private double accuracy; 
private double bearing; 
public Getters/Setters.. 
public Detection(String vehicleId,String historyDate, double lat,double lon,double speed,double accuracy,double bearing) { 
    this.vehicleId=vehicleId; 
    this.historyDate=historyDate; 
    this.lat=lat; 
    this.lon=lon; 
    this.speed=speed; 
    this.accuracy=accuracy; 
    this.bearing=bearing; 
} 

}

這裏是一個異步任務的POST電話：

class postTask extends AsyncTask<Detection,Void,Void>{ 
    @Override protected void onPreExecute() { 

    } 
    @Override 
    protected Void doInBackground(Detection... params) { 
     try{ 
      // Set the Content-Type header 
      HttpHeaders requestHeaders = new HttpHeaders(); 
      requestHeaders.setContentType(new MediaType("application","json")); 
      HttpEntity<Detection> requestEntity = new HttpEntity<Detection>(params[0], requestHeaders); 

      // Create a new RestTemplate instance 
      RestTemplate restTemplate = new RestTemplate(); 

      // Add the Jackson and String message converters 
      restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter()); 
      restTemplate.getMessageConverters().add(new StringHttpMessageConverter()); 

      // Make the HTTP POST request, marshaling the request to JSON, and the response to a String 
      ResponseEntity<String> responseEntity = restTemplate.exchange("http://wsonline.pladema.net/Monitores.WS/api/androids", HttpMethod.POST, requestEntity, String.class); 
      String result = responseEntity.getBody(); 
     } 
     catch (Exception e){ 
      Log.e("MainActivity", e.getMessage(), e); 
     } 
     return null; 
    } 
}

調試打破在restTemplate.exchange（）方法，並已經檢查參數不爲空。這是錯誤消息

03-22 12:34:44.635 4533-4654/gps.example.com.myapplicationgps E/MainActivity: Could not read JSON: Can not deserialize instance of java.lang.String out of START_OBJECT token 
                      at [Source: buffer([email protected]9bdd7c).inputStream(); line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token 
                      at [Source: buffer([email protected]9bdd7c).inputStream(); line: 1, column: 1] 
                      org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Can not deserialize instance of java.lang.String out of START_OBJECT token 
                      at [Source: buffer([email protected]9bdd7c).inputStream(); line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token 
                      at [Source: buffer([email protected]9bdd7c).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$ResponseEntityResponseExtractor.extractData(RestTemplate.java:655) 
                       at org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:641) 
                       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.exchange(RestTemplate.java:415) 
                       at gps.example.com.myapplicationgps.MainActivity$postTask.doInBackground(MainActivity.java:202) 
                       at gps.example.com.myapplicationgps.MainActivity$postTask.doInBackground(MainActivity.java:182) 
                       at android.os.AsyncTask$2.call(AsyncTask.java:292) 
                       at java.util.concurrent.FutureTask.run(FutureTask.java:237) 
                       at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
                       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
                       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
                       at java.lang.Thread.run(Thread.java:818) 
                      Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token 
                      at [Source: buffer([email protected]9bdd7c).inputStream(); line: 1, column: 1] 
                       at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:691) 
                       at com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:46) 
                       at com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:11) 
                       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) 
                       ... 15 more

對不起，您收到的英語不好

來源

2016-03-22 martin cremona

的反應顯然是application/json，這就是爲什麼Jackson踢，並試圖解析一個JSON對象。你應該指定一個Accept header指示的媒體類型是可以接受的響應：

requestHeaders.setAccept(new MediaType("text","plain"));

這樣的StringHttpMessageConverter應由RestTemplate用來響應轉換 - 如果遠程服務器支持服務text/plain您的要求資源。

來源

2016-03-22 15:29:59 msparer

對不起。我沒有寫，因爲它一遍又一遍地說。順便說一句，我現在將編輯它 –

，它不是默認的構造函數，但謝謝！ –

@martincremona我更新了我的回答 – msparer

無法讀取JSON：無法將START_OBJECT令牌的java.lang.String實例反序列化（非常簡單的對象）

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