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Error parsing field as object or array

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闹比i
闹比i 2021-01-20 08:23

i have the following Json string, which I\'m suppose to deserialize. The problem is: since this string comes from a server I can\'t change it and I need to deserialize as PO

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  • 心在旅途
    心在旅途 (楼主)
    2021-01-20 09:00

    You can use TypeAdapterFactory to do the conversion. Here is a factory that will add that functionality to all of your List member types --

    import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.JsonWriter;
import java.io.IOException;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Collections;
import java.util.List;

public class SingletonListTypeAdapterFactory implements TypeAdapterFactory {
     public  TypeAdapter create(Gson gson, TypeToken typeToken) {

       Type type = typeToken.getType();
       if (typeToken.getRawType() != List.class
           || !(type instanceof ParameterizedType)) {
         return null;
       }
       Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
       TypeAdapter elementAdapter = gson.getAdapter(TypeToken.get(elementType));
       TypeAdapter arrayAdapter = gson.getDelegateAdapter(this, typeToken);
       return (TypeAdapter) newSingtonListAdapter((TypeAdapter) elementAdapter, (TypeAdapter>) arrayAdapter);
     }

     private  TypeAdapter> newSingtonListAdapter(
         final TypeAdapter elementAdapter,
         final TypeAdapter> arrayAdapter) {
       return new TypeAdapter>() {

         public void write(JsonWriter out, List value) throws IOException {
           if(value == null || value.isEmpty()) {
             out.nullValue();
           } else if(value.size() == 1) {
            elementAdapter.write(out, value.get(0));
           } else {
             arrayAdapter.write(out, value);
           }
         }

         public List read(JsonReader in) throws IOException {
           if (in.peek() != JsonToken.BEGIN_ARRAY) {
             E obj = elementAdapter.read(in);
             return Collections.singletonList(obj);
           }
           return arrayAdapter.read(in);
         }
       };
     }
   }



    As bonus, it also serializes in the same way, if needed.  If you also want to serialize as array, replace the write method with a call to arrayAdapter.write.
    


    To you, add to your gson when building --
    


    Gson gson = new GsonBuilder().registerTypeAdapterFactory(new SingletonListTypeAdapterFactory())
        .create();

    
    
    
             
    
                                                        
    
            
            
    
              
                
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