android - Retrofit/OkHttp3: Create and access custom RequestBody with an Interceptor -

i posting backend. service looks this:

public interface thingservice {      @post("thing/")     @headers("content-type: application/json")     single<result<thing>> postthing(@body @nonnull requestbody body); } 

and interceptor this:

public class thinginterceptor implements interceptor {      @override     public response intercept(@nonnull chain chain) throws ioexception {         return chain.proceed(getthingedrequest(chain.request()));     }      @nonnull     private request getthingedrequest(request request) {         string thing = getthing(request.body());          httpurl newurl = request.url().newbuilder()                 .addqueryparameter("thing", thing)                 .build();         return request.newbuilder().url(newurl).build();     }      private string getthing(requestbody body) {         thingrequestbody thingbody = (thingrequestbody) body; // no good, see below         return thingbody.getthing();     } } 

here's thingrequestbody:

public static final class thingrequestbody extends requestbody {      private final requestbody delegate;     private final string thing;      public thingrequestbody(@nonnull requestbody delegate, @nonnull string thing) {         this.delegate = delegate;         this.thing = thing;     }      // why want own requestbody, can attach metadata later     // via thinginterceptor     @nonnull public string getthing() {         return body;     }      // boilerplate omitted } 

and measure, create instance of thingrequestbody so:

    @nonnull     public requestbody build() {         mediatype json = mediatype.parse("application/json; charset=utf-8");          gson gson = gsonadapterfactory.getgson();         string body = gson.tojson(things); // list of things         requestbody delegate = requestbody.create(json, body);         return new thingrequestbody(delegate, body);         // in case not clear, `body` here string representation of          // `content` byte-encoded inside requestbody delegate } 

this approach falls flat on face, because okhttp3, in class requestbuilder, wrap thingrequestbody in instance of contenttypeoverridingrequestbody, assigning thingrequestbody private delegate field. unfortunately, contenttypeoverridingrequestbody private, , delegate. can access them via reflection.

i can think of 2 solutions: 1. make contenttypeoverridingrequestbody public , expose delegate, or 2. change design.

edit

quick update, have discovered easy way access string representation of encoded body via okio's buffer (try/catch boilderplate omitted):

buffer buffer = new buffer(); body.writeto(buffer); json = buffer.readstring(charset.forname("utf-8")); 

and guess that's fine, why okhttp3 force use of internal private contenttypeoverridingrequestbody class?