How to use

findOne

method

in

io.vertx.ext.mongo.MongoService

public io.vertx.rxjava.ext.mongo.MongoService findOne(String collection, JsonObject query, JsonObject fields, Handler<AsyncResult<JsonObject>> resultHandler) { 
 delegate.findOne(collection, query, fields, resultHandler);
 return this;
}

public static io.vertx.ext.mongo.MongoService findOne(io.vertx.ext.mongo.MongoService j_receiver, java.lang.String collection, java.util.Map<String, Object> query, java.util.Map<String, Object> fields, io.vertx.core.Handler<io.vertx.core.AsyncResult<java.util.Map<String, Object>>> resultHandler) {
 io.vertx.core.impl.ConversionHelper.fromObject(j_receiver.findOne(collection,
  query != null ? io.vertx.core.impl.ConversionHelper.toJsonObject(query) : null,
  fields != null ? io.vertx.core.impl.ConversionHelper.toJsonObject(fields) : null,
  resultHandler != null ? new io.vertx.core.Handler<io.vertx.core.AsyncResult<io.vertx.core.json.JsonObject>>() {
  public void handle(io.vertx.core.AsyncResult<io.vertx.core.json.JsonObject> ar) {
   resultHandler.handle(ar.map(event -> io.vertx.core.impl.ConversionHelper.fromJsonObject(event)));
  }
 } : null));
 return j_receiver;
}
public static io.vertx.ext.mongo.MongoService findOneAndUpdate(io.vertx.ext.mongo.MongoService j_receiver, java.lang.String collection, java.util.Map<String, Object> query, java.util.Map<String, Object> update, io.vertx.core.Handler<io.vertx.core.AsyncResult<java.util.Map<String, Object>>> resultHandler) {