Parsing a composed JSON file using gson in Android

Question

I have three nested classes as the following:

public class A {
   String s1;
   String s2;
   String s3;
   String s4;
   String s5;
   String s6;
   String s7;
   String s8;
   B b;
}

public class B{
   private Map<String, C> ag = new HashMap<>();
}

public class C{
   private Map<String, Boolean> ar = new HashMap<>();
}

Class A is sent as a GET method reply of type JSON to an Android app which consumes the service as shown bellow:

Gson gson = new GsonBuilder()
   .enableComplexMapKeySerialization()
   .setLenient()
   .create();

Retrofit r = new Retrofit.Builder()
   .baseUrl(url)
   .addConverterFactory(GsonConverterFactory.create(gson))
   .build();

...

However, when running the Android app, I get the following error:

E/Rest GET Error: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line ? column ? B.ag.

Having in mind that If I remove class b field from class A, everything goes smoothly. It seems that gson is unable to deserialize a composed JSON file. So what to do?

Note: The JSON file is retrieved successfully from a Restful webservice using MOXy not Jackson. So there is no option to use @JsonDeserialize.

Below is the returned JSON file:

{"b":{"ag":{"entry":[{"key":"AS2","value":{"ar":{"entry":[{"key":"s1","value":false},{"key":"s2","value":false},{"key":"s3","value":false},{"key":"s4","value":false},{"key":"s5","value":false},{"key":"s6","value":true},{"key":"s7","value":false},{"key":"s8","value":false}]}}},{"key":"AS3","value":{"ar":{"entry":[{"key":"s1","value":false},{"key":"s2","value":true},{"key":"s3","value":true},{"key":"s4","value":false},{"key":"s5","value":false},{"key":"s6","value":false},{"key":"s7","value":false},{"key":"s8","value":true}]}}},{"key":"AS1","value":{"ar":{"entry":[{"key":"s1","value":false},{"key":"s2","value":true},{"key":"s3","value":true},{"key":"s4","value":false},{"key":"s5","value":false},{"key":"s6","value":false},{"key":"s7","value":false},{"key":"s8","value":false}]}}}]}},"s1":"string1","s2":"string2","s3":"string3","s4":"string4","s5":"string5","s6":"string6","s7":"string7","s8":"string8"}

Answer 1

From your class and error provided it seem that you are getting Array at B b; in Class A . We can say exact problem if you share jsonResponse.

----Updated---

Change your Class B

Class B{
    private Ag ag;
}

class Ag {
    List<Entry> entry;
}

class Entry{
    String key;
    Value value;
}

class Value{
    Ar ar;
}

class Ar{
    List<ArEntry> entry;
}

class ArEntry{
    String key;
    Boolean value;
}

This is how your classes for the jsonResponse you provided.

You can convert any json response to pojo here or you can add Android Studio plugin here .