Java Parse Json with array with different object types (Gson or Jackson or etc.)

Question

 {
   "response": {
     "data": {
       "333": [
         {
           "id": "69238",
           "code": "545"
         },
         {
           "id": "69239",
           "code": "545",
           "marked": "123"
         }
       ],
       "544": [
         {
           "id": "69906",
           "code": "544",
           "marked": "123"
         },
         {
           "id": "69907",
           "code": "544"
         }
       ],
       "890": [
         {
           "id": "69238",
           "code": "545",
           "marked": "123"
         },
         {
           "id": "69239",
           "code": "545"
         }
       ]
     }
   }
 }

I have this JSON data as a response and try to mapping. Unfortunately I can't.

The first reason is index of objects are changeable. For example one index 890 and other one is 544.

The second reason is count of items in object are different.

When I try to create java classes with www.jsonschema2pojo.org. I get lots of classes with underscore + integer. For example;

 import com.google.gson.annotations.Expose;
 import com.google.gson.annotations.SerializedName;
 import org.apache.commons.lang.builder.EqualsBuilder;
 import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.apache.commons.lang.builder.ToStringBuilder;

 public class _544 {

     @SerializedName("id")
     @Expose
     private String id;
     @SerializedName("code")
     @Expose
     private String code;
     @SerializedName("marked")
     @Expose
     private String marked;

     public String getId() {
         return id;
     }

     public void setId(String id) {
         this.id = id;
     }

     public String getCode() {
         return code;
     }

     public void setCode(String code) {
         this.code = code;
     }

     public String getMarked() {
         return marked;
     }

     public void setMarked(String marked) {
         this.marked = marked;
     }

     @Override
     public String toString() {
         return ToStringBuilder.reflectionToString(this);
     }

     @Override
     public int hashCode() {
         return new HashCodeBuilder().append(id).append(code).append(marked).toHashCode();
     }

     @Override
     public boolean equals(Object other) {
         if (other == this) {
             return true;
         }
         if ((other instanceof _544) == false) {
             return false;
         }
         _544 rhs = ((_544) other);
         return new EqualsBuilder().append(id, rhs.id).append(code, rhs.code).append(marked, rhs.marked).isEquals();
     }

 }    

and the other one is like this

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.ToStringBuilder;

public class _890 {

    @SerializedName("id")
    @Expose
    private String id;
    @SerializedName("code")
    @Expose
    private String code;
    @SerializedName("marked")
    @Expose
    private String marked;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getMarked() {
        return marked;
    }

    public void setMarked(String marked) {
        this.marked = marked;
    }

    @Override
    public String toString() {
        return ToStringBuilder.reflectionToString(this);
    }

    @Override
    public int hashCode() {
        return new HashCodeBuilder().append(id).append(code).append(marked).toHashCode();
    }

    @Override
    public boolean equals(Object other) {
        if (other == this) {
            return true;
        }
        if ((other instanceof _890) == false) {
            return false;
        }
        _890 rhs = ((_890) other);
        return new EqualsBuilder().append(id, rhs.id).append(code, rhs.code).append(marked, rhs.marked).isEquals();
    }

}

The numbers 544 or 890 etc. are dynamic

So how can I do mapping with this dynamic indexed data with Java?

Thanks for help.

Answer 1

You can use a custom deserializer. The below example is using Gson, but the same thing can be done with Jackson.

class CustomDeserializer implements JsonDeserializer<Response> {

    @Override
    public Response deserialize(JsonElement jsonElement, Type typeOfElement, JsonDeserializationContext context) throws JsonParseException {
        JsonObject data = jsonElement.getAsJsonObject().get("response").getAsJsonObject().get("data").getAsJsonObject();
        Type listType = new TypeToken<List<Data>>() {}.getType();
        Map<String, List<Data>> dataMap = new HashMap<String, List<Data>>();

        for (Map.Entry<String, JsonElement> entry : data.entrySet()) {
            List<Data> dataList = context.deserialize(entry.getValue(), listType);

            dataMap.put(entry.getKey(), dataList);
        }

        return new Response(dataMap);
    }
}

In the main class:

String json = "...";

Gson gson = new GsonBuilder().registerTypeAdapter(Response.class, new CustomDeserializer()).create();

System.out.println(gson.fromJson(json, Response.class));

Class for the response:

class Response {
    private Map<String, List<Data>> data;

    public Response(Map<String, List<Data>> data) {
        this.data = data;
    }
}

Class for each data object:

class Data {
    private String id;
    private String code;
    private String mark;
}

The response here will have a map of each data entry and a list of its values. (ex: 333 -> list of Data objects), but you can change the deserializer to have the key (333) to be one of the variables of the Data object and assign it in the for loop.