Deserialize JSON using Retrofit to Room Embedded Class

Question

I'm receiving this JSON from my server. My requirement is slightly different than usual use-cases hence this question. In my case I'm using @Embedded provided by Room library.

[
{
    "id": 105,
    "title": "Clear notification",
    "message": "Opening the app should automatically clear the notifications",
    "klass": "Demo",
    "priority": 0,
    "timestamp": "2017-09-03T07:20:56.130500Z",
    "teacher": "ABC",
    "attachments": []
},
{
    "id": 104,
    "title": "Attachment",
    "message": "File upload take 1",
    "attachments": [
        {
            "id": 5,
            "name": "Technology List.txt",
            "url": "https://cdn.filestackcontent.com/",
            "type": "text/plain",
            "size": 954
        }
    ]
}

]

The POJO's for the above JSON. I'm de-serializing JSON to FeedWithAttachment class.

public class FeedWithAttachment {
    @NotNull @Embedded
    public Feed feed; 
    @Relation(parentColumn = "id", entityColumn = "feedId", entity = Attachment.class)       
    public List<Attachment> attachments;

}

My Feed class:

data class Feed(
        @PrimaryKey @SerializedName("id")
        var id: Long = 0,

        @SerializedName("title")
        var title: String = "",

        @SerializedName("message")
        var message: String = "",
)

My attachment class:

data class Attachment(
        @PrimaryKey @SerializedName("id")
        var attachmentId: Int = 0,
        var name: String = "",
        var url: String = "",
        var type: String = "",
        var size: Long = 0,
        @Transient
        var feedId: Long = 0
)

If we put List<Attachment in the Feed model then it works as expected. Unfortunately my requirements are such that I need another class called as FeedWithAttachment.

Retrofit:

interface FeedService {
    public Call<List<FeedWithAttachment>> getFeeds();
}

---

The problem

I'm getting FeedWithAttachment in the response where feed is null and attachments is as expected.

Answer 1

When you write feed variable in FeedWithAttachment, retrofit try to find "feed" in keys in json. each variable name defined in class must exist in json's key. you use this class:

public class FeedWithAttachment {
    int id;
    String title;
    String message;
    String klass;
    int priority;
    String timestamp;
    String teacher;

    List<Attachment> attachments;
}

and Attachment.class :

public class Attachment{
    int id;
    String name;
    String url;
    String type;
    int size;
}