Get list of subobjects by using gson

Question

I have a json:

{
  "mainObject": "firstMainObject",
  "mainObjectInfo": {
    "firstInfo": "1",
    "secondInfo": "2"
  },
  "values": [
    {
      "valueName": "111",
      "valueList": {
        "details": [
          "111FirstDetails",
          "111SecondDetails"
        ],
        "valueDescription": "desc1",
        "detailsInfo": "111detailsInfo"
      },
      "endValue": "11End"
    },
    {
      "valueName": "222",
      "valueList": {
        "details": [
          "222FirstDetails",
          "222SecondDetails"
        ],
        "valueDescription": "desc2",
        "detailsInfo": "222detailsInfo"
      },
      "endValue": "22End"
    },
    {
      "valueName": "333",
      "valueList": {
        "details": [
          "333FirstDetails",
          "333SecondDetails"
        ],
        "valueDescription": "desc3",
        "detailsInfo": "333detailsInfo"
      },
      "endValue": "33End"
    }
  ],
  "lastInfo": "ok"
}

I want to extract List of valueDescription and detailsInfo valus from valueList.

I created a class:

public class MyObject {

    @SerializedName("valueDescription")
    String valueDescription;

    @SerializedName("detailsInfo")
    String detailsInfo;

}

and then use:

Gson gson = new Gson();
List<MyObject> myObject = gson.fromJson(myJson,new TypeToken<ArrayList<MyObject>>(){}.getType());

but something goes wrong and there is an error:

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2 path $
    at com.google.gson.Gson.fromJson(Gson.java:900)
    at com.google.gson.Gson.fromJson(Gson.java:853)
    at com.google.gson.Gson.fromJson(Gson.java:802)
    at com.package.MyClass.myMethod(MyClass.java:95)
    at com.package.MyClass.myMethod(MyClass.java:33)
    at com.atlassian.stash.internal.hook.repository.DefaultRepositoryHookService.postUpdate(DefaultRepositoryHookService.java:788)
    at com.atlassian.stash.internal.hook.repository.DefaultRepositoryHookService.doPostUpdate(DefaultRepositoryHookService.java:595)
    at com.atlassian.stash.internal.hook.repository.DefaultRepositoryHookService.postUpdate(DefaultRepositoryHookService.java:362)
    at com.atlassian.stash.internal.hook.repository.CoreRefChangeEventToRepositoryHookAdapter.onRefsChanged(CoreRefChangeEventToRepositoryHookAdapter.java:55)
    at com.atlassian.event.internal.SingleParameterMethodListenerInvoker.invoke(SingleParameterMethodListenerInvoker.java:40)
    at com.atlassian.stash.internal.event.AsyncBatchingInvokersTransformer$AsyncInvokerBatch.invoke(AsyncBatchingInvokersTransformer.java:109)
    at com.atlassian.event.internal.AsynchronousAbleEventDispatcher$1$1.run(AsynchronousAbleEventDispatcher.java:38)
    at com.atlassian.sal.core.executor.ThreadLocalDelegateRunnable.run(ThreadLocalDelegateRunnable.java:34)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at com.atlassian.stash.internal.event.EventThreadFactory.lambda$createThread$0(EventThreadFactory.java:24)
    at java.lang.Thread.run(Thread.java:745)
    ... 31 frames trimmed
Caused by: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2 path $
    at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:350)
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:80)
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:61)
    at com.google.gson.Gson.fromJson(Gson.java:888)
    ... 16 common frames omitted

I want a list of MyObject object like:

1) consists valueDescription = desc1 and detailsInfo = 111detailsInfo

2) consists valueDescription = desc2 and detailsInfo = 222detailsInfo

3) consists valueDescription = desc3 and detailsInfo = 333detailsInfo

How is it possible to extract this values from my json?

Answer 1

You're trying to parse a JSON Object as a JSON Array.

What you're looking for is something like this:

Used to parse the entire object:

public class WrapperObject {
    @SerializedName("values")
    List<ValueObject> values;

    public List<ValueObject> getValues(){
        return values;
    }
}

Properties wrapper:

public class ValueObject{
     @SerializedName("valueList")
     MyObject valueList;

     public MyObject getValueList(){
         return valueList;
     }
}

Required information:

public class MyObject{
    @SerializedName("valueDescription")
    String valueDescription;

    @SerializedName("detailsInfo")
    String detailsInfo;
}

parsing:

WrapperObject wrapperObject = new Gson().fromJson(myJson, WrapperObject.class);