JsonMappingException: No suitable constructor found for type

Question

Given the api endpoint

@ApiMethod(name = "sendChallenge", httpMethod = HttpMethod.POST)
public ExchangeList sendChallenge(ChallengeData request) throws Exception {
  return getFromDBThenProcess(request);
}

And the front end (android) call to endpoint

ExchangeList transfers = service.sendChallenge(request).execute();

I get the following stack trace from the LogCat.

Note: I am monitoring my server console (localhost) and no call came in.

Stacktrace:

04-08 14:58:53.261: D/dalvikvm(940): GC_CONCURRENT freed 1394K, 15% free 12495K/14599K, paused 15ms+15ms, total 75ms
… //[many of those `freed` lines]
04-08 14:58:54.742: D/dalvikvm(940): GC_CONCURRENT freed 1394K, 15% free 12506K/14599K, paused 15ms+16ms, total 85ms
04-08 14:58:55.562: W/System.err(940): com.google.api.client.googleapis.json.GoogleJsonResponseException: 400 Bad Request
04-08 14:58:55.562: W/System.err(940): {
04-08 14:58:55.562: W/System.err(940):   "code": 0,
04-08 14:58:55.562: W/System.err(940):   "message": "com.google.appengine.repackaged.org.codehaus.jackson.map.JsonMappingException: No suitable constructor found for type [simple type, class com.myapi.games.message.ChallengeData]: can not instantiate from JSON object (need to add/enable type information?)\n at [Source: N/A; line: -1, column: -1]"
04-08 14:58:55.572: W/System.err(940): }
04-08 14:58:55.572: W/System.err(940):  at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:111)
04-08 14:58:55.572: W/System.err(940):  at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:38)
04-08 14:58:55.572: W/System.err(940):  at com.google.api.client.googleapis.services.AbstractGoogleClientRequest$1.interceptResponse(AbstractGoogleClientRequest.java:314)
04-08 14:58:55.572: W/System.err(940):  at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1060)
04-08 14:58:55.572: W/System.err(940):  at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:412)
04-08 14:58:55.572: W/System.err(940):  at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:345)
04-08 14:58:55.572: W/System.err(940):  at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:463)
04-08 14:58:55.572: W/System.err(940):  at com.myapi.games.utils.sendChallenge.doInBackground(sendChallenge.java:70)
04-08 14:58:55.582: W/System.err(940):  at com.myapi.games.utils.sendChallenge.doInBackground(sendChallenge.java:1)
04-08 14:58:55.582: W/System.err(940):  at android.os.AsyncTask$2.call(AsyncTask.java:287)
04-08 14:58:55.582: W/System.err(940):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
04-08 14:58:55.582: W/System.err(940):  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
04-08 14:58:55.582: W/System.err(940):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
04-08 14:58:55.592: W/System.err(940):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
04-08 14:58:55.592: W/System.err(940):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
04-08 14:58:55.592: W/System.err(940):  at java.lang.Thread.run(Thread.java:856)

This is about an appengine connected android project. Everything compiles without errors, etc. Also the POJO ChallengeData is made of three other POJOs similar to:

public class ChallengeData{

  Credit credit;
  Coin  coin;
  Friend friend;

  //getters and setters
}

Then both Credit and Coin only contain simple fields (i.e. int and String) but Friend contains some simple fields and a further POJO.

I really don't think the depth of the JSON (i.e. POJO relations) should matter. But I include the details all the same.

Answer 1

You may be getting this error because you are sending images through your endpoint api AND you forgot to encode them in Base64. You must encode all images into a base64 string. Here is a link with code snippet showing how to do this. Rememeber you are encoding from byte to String. The reason I guess thus is because you mention your server is not getting any hit and yet you are getting a 400 Bad Request error, which means google is intercepting your call and is not able to parse the request. So try it out.