I have the following class hierarchy
public abstract class SyncModel {
@Expose
@SerializedName("id")
private Long globalId;
@Expose
protected DateTime lastModified;
/* Constructor, methods... */
}
public class Event extends SyncModel {
@Expose
private String title;
/* Other fields, constructor, methods... */
}
I need to send an Event instance to backend.
@Body
When I post the Event instance in a request body, it is serialized fine.
RetroFit Java interface:
public interface EventAPI {
@POST("/event/create")
void sendEvent(@Body Event event, Callback<Long> cbEventId);
}
RetroFit log:
D Retrofit ---> HTTP POST http://hostname:8080/event/create D Retrofit Content-Type: application/json; charset=UTF-8 D Retrofit Content-Length: 297 D Retrofit {"title":"Test Event 01",...,"id":null,"lastModified":"2015-07-09T14:17:08.860+03:00"} D Retrofit ---> END HTTP (297-byte body)
@Field
But when I post the Event instance in a request parameter, only abstract class is serialized.
RetroFit Java interface:
@FormUrlEncoded
@POST("/event/create")
void sendEvent(@Field("event") Event event, Callback<Long> cbEventId);
RetroFit log:
D Retrofit ---> HTTP POST http://hostname:8080/event/create D Retrofit Content-Type: application/x-www-form-urlencoded; charset=UTF-8 D Retrofit Content-Length: 101 D Retrofit event=SyncModel%28globalId%3Dnull%2C+lastModified%3D2015-07-09T13%3A36%3A33.510%2B03%3A00%29 D Retrofit ---> END HTTP (101-byte body)
Notice the difference.
Why?
How can I send a serialized Event instance to backend in a request parameter?
Do I need to write a custom JSON serializer for abstract class? (example: Polymorphism with JSON)
Or is it a RetroFit specific feature (to ignore child classes)?
I've also noticed that in the 2nd case globalId
field serialized name is globalId
, but it should be id
! It makes me think that RetroFit uses a different GsonConverter
for @Field
than for @Body
parameters...
Gradle dependencies
compile 'com.squareup.retrofit:retrofit:1.9.+'
compile 'com.squareup.okhttp:okhttp:2.3.+'
compile 'net.danlew:android.joda:2.8.+'
compile ('com.fatboyindustrial.gson-jodatime-serialisers:gson-jodatime-serialisers:1.1.0') { // GSON + Joda DateTime
exclude group: 'joda-time', module: 'joda-time'
}
REST client
public final class RESTClient {
// Not a real server URL
public static final String SERVER_URL = "http://hostname:8080";
// one-time initialization
private static GsonBuilder builder = new GsonBuilder()
.serializeNulls()
.excludeFieldsWithoutExposeAnnotation()
.setDateFormat("yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'SSS'Z'");
// Joda DateTime type support
private static Gson gson = Converters.registerDateTime(builder).create();
private static RestAdapter restAdapter = new RestAdapter.Builder()
.setLogLevel(RestAdapter.LogLevel.FULL) // for development
.setEndpoint(SERVER_URL)
.setConverter(new GsonConverter(gson)) // custom converter
.build();
private static final EventAPI eventService = restAdapter.create(EventAPI.class);
/* + Getter for eventService */
static {
// forget them
restAdapter = null;
gson = null;
builder = null;
}
}
Call
RESTClient.getEventService().sendEvent(event, new Callback<Long>() {/* ... */});
Take a look at @Field
's documentation. It says:
Values are converted to strings using
String#valueOf(Object)
and then form URL encoded.
String#valueOf(Object)
makes a call to Object#toString()
inside. I suppose your SyncModel
has a toString()
method and Event
does not. When Retrofit calls String.valueOf(event)
, SyncModel#toString()
is called instead of Event#toString()
. That's why you don't see title
in the Retrofit logs.
Gson doesn't play any role at all when converting @Field
parameters. It can be though - you can make your toString()
method look something like this:
@Override
public String toString() {
return GsonProvider.getInstance().toJson(this);
}
Put this inside your abstract SyncModel
class and it should work for Event
as well.
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