Feign QueryMap usage with POJO

Question

I've found in FEIGN-README that I can do stuff like:

interface MarketDataRestClient {
    @RequestLine("GET /api/v1/depth")
    fun getOrderBook(@QueryMap orderBookQuery: OrderBookQuery) : OrderBook
}

OrderBookQuery:

data class OrderBookQuery(val symbol: String, val limit: Int? = 100)

And Feign should generate query params: /api/v1/depth?symbol={symbol}&limit={limit}

Unfortunately all I'm getting is:

Exception in thread "main" java.lang.IllegalStateException: QueryMap parameter must be a Map: class OrderBookQuery
at feign.Util.checkState(Util.java:128)
at feign.Contract$BaseContract.parseAndValidateMetadata(Contract.java:126)
at feign.Contract$BaseContract.parseAndValidatateMetadata(Contract.java:64)
at feign.ReflectiveFeign$ParseHandlersByName.apply(ReflectiveFeign.java:146)
at feign.ReflectiveFeign.newInstance(ReflectiveFeign.java:53)
at feign.Feign$Builder.target(Feign.java:198)
at feign.Feign$Builder.target(Feign.java:194)

Answer 1

This feature will be available in 9.7. The current published version, as of the writing of this answer, is 9.6. If you do not want to wait, please clone the repository and run build the project.

Answer 2

Just add a QueryMapEncoder,like?

return Feign
        .builder()
        .client(new OkHttpClient())
        .logger(new Logger.ErrorLogger()).logLevel(Logger.Level.BASIC)
        .queryMapEncoder(new BeanQueryMapEncoder())
        .encoder(new GsonEncoder())
        .decoder(new GsonDecoder())