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Ich benutze Spring in Android, um einen POST-Aufruf zu machen, wenn der obige Fehler auftritt. Ich habe gesehen, dass alle Antworten dieses Problem betreffen, aber in allen scheinen sie Arrays oder Listen in dem Objekt zu haben, das sie in JSON transformieren wollen. Mine ist sehr einfach:Konnte JESON nicht lesen: Instanz von java.lang.String kann nicht aus START_OBJECT-Token deserialisiert werden (sehr einfaches Objekt)
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;
}
}
Hier ist der POST Anruf von einer asynchronen Aufgabe:
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;
}
}
die Debug bricht an der restTemplate.exchange() -Methode und bereits überprüfen Sie die Parameter nicht null ist. Dies ist die Fehlermeldung
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
Sorry für die schlechte Englisch
Entschuldigung dafür. Ich habe es nicht geschrieben, weil es immer und immer wieder dasselbe sagt. Ich werde es jetzt bearbeiten –
übrigens, es war nicht der Standard-Konstruktor, aber trotzdem danke! –
@martincremona Ich aktualisierte meine Antwort – msparer