title: POST not possible because instantiation of standard serializer (Jackson) fails
body: <p>I'm trying to post data from my client to a rest-webserver.
  My client uses Spring's Resttemplate for Android.</p>
  
  <p>Requesting objects works, but POSTing them runs in the following error:</p>
  
  <pre><code>java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.erdi.mobilefinalneu/com.example.erdi.mobilefinalneu.UploadActivity}: java.lang.IllegalStateException: Failed to instantiate standard serializer (of type com.fasterxml.jackson.databind.ser.std.NullSerializer): access to constructor not allowed
  
  Caused by: java.lang.IllegalStateException: Failed to instantiate standard serializer (of type com.fasterxml.jackson.databind.ser.std.NullSerializer): access to constructor not allowed
  </code></pre>
  
  <p>The relevant code is:</p>
  
  <pre><code>    restTemplate = new RestTemplate();
      restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
      //restTemplate.getMessageConverters().add(new MappingJacksonHttpMessageConverter());
      StrictMode.ThreadPolicy policy = new
              StrictMode.ThreadPolicy.Builder()
              .permitAll().build();
      StrictMode.setThreadPolicy(policy);
  
      HttpHeaders headers = new HttpHeaders();
      headers.setContentType(MediaType.APPLICATION_JSON);
  
      HttpEntity&lt;RecordingModel&gt; entity = new HttpEntity&lt;RecordingModel&gt;(recordingToPost,headers);
  
      restTemplate.put(url + "sportsupload/", entity);
      //ResponseEntity&lt;RecordingModel&gt; out = restTemplate.exchange(url + "sportsupload/", HttpMethod.POST, entity
      //        , RecordingModel.class);
      //restTemplate.postForLocation(url + "sportsupload/", recordingToPost);
  </code></pre>
  
  <p>(as you can see in the commented lines, I tried different ways to post an object, but all had these error message)</p>
  
  <p>My RecordingModel-object looks like the following:</p>
  
  <pre><code>@JsonIgnoreProperties(ignoreUnknown = true)
  //@JsonSerialize(include=JsonSerialize.Inclusion.NON_NULL)
  public class RecordingModel {
  private String upload_date;
  private String recording_date;
  private String name;
  private String user;
  private String video;
  private List&lt;String&gt; sensors = new ArrayList&lt;String&gt;();
  
  public String getName(){
      return name;
  }
  
  public List&lt;String&gt; getSensors() {
      return sensors;
  }
  
  public String getRecording_date() {
      return recording_date;
  }
  
  public String getUpload_date() {
      return upload_date;
  }
  
  public String getUser() {
      return user;
  }
  
  public String getVideo() {
      return video;
  }
  
  public void getRecordingDetails(){
      if(upload_date != null){
          Log.d("RecordingModel", upload_date);
      }
      if(recording_date != null){
          Log.d("RecordingModel", recording_date);
      }
      if(name != null){
          Log.d("RecordingModel", name);
      }
      if(user != null){
          Log.d("RecordingModel", user);
      }
      if(video != null){
          Log.d("RecordingModel", video);
      }
      for(String sensor : sensors){
          Log.d("RecordingModel", sensor);
      }
  }
  
  public void setName(String name) {
      this.name = name;
  }
  
  public void setRecording_date(String recording_date) {
      this.recording_date = recording_date;
  }
  
  public void setSensors(List&lt;String&gt; sensors) {
      this.sensors = sensors;
  }
  
  public void setUpload_date(String upload_date) {
      this.upload_date = upload_date;
  }
  
  public void setUser(String user) {
      this.user = user;
  }
  
  public void setVideo(String video) {
      this.video = video;
  }
  </code></pre>
  
  <p>}</p>
  
  <p>As you can see, I tried to use JSONSerialize there, but that also did not work.</p>
  
  <p>Has anyone of you an idea what I am doing wrong? Googling/Stackoverflowing arround did not help me...</p>