Java okHttp 2-way handshake SSL

Question

Hi I can't find solution, how can I put my cert to sign REST API request, for 2-way handshake?

My code:

        HttpUrl.Builder httpUrlBuilder = httpUrl.newBuilder();
        Request.Builder builder = new Request.Builder()
                .url(httpUrlBuilder.build())
                .post(okhttp3.RequestBody.create(okhttp3.MediaType.parse("application/json; charset=utf-8"), body));
        for (Map.Entry<String, String> header : headers.entrySet()) {
            builder.addHeader(header.getKey(), header.getValue());
        }
        Request request = builder.build();
        OkHttpClient httpClient = new OkHttpClient.Builder().sslSocketFactory(SSLContext.getDefault().getSocketFactory()).build();
        Response response = httpClient.newCall(request).execute();
        String res =  response.body().string();
        System.out.print("Response: " +res);

Im using SpringBoot framework and cert is loaded by:

server.ssl.key-store=certFile.pfx
server.ssl.key-store-password=****
server.ssl.keyStoreType=PKCS12
security.require-ssl=true

This code works correctly, but without cert sign is useless for me