code: public Observable<ExpressRouteConnectionInner> getAsync(String resourceGroupName, String expressRouteGatewayName, String connectionName) {
          return getWithServiceResponseAsync(resourceGroupName, expressRouteGatewayName, connectionName).map(new Func1<ServiceResponse<ExpressRouteConnectionInner>, ExpressRouteConnectionInner>() {
              @Override
              public ExpressRouteConnectionInner call(ServiceResponse<ExpressRouteConnectionInner> response) {
                  return response.body();
              }
          });
      }
docs: Gets the specified ExpressRouteConnection.
  
  @param resourceGroupName The name of the resource group.
  @param expressRouteGatewayName The name of the ExpressRoute gateway.
  @param connectionName The name of the ExpressRoute connection.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the ExpressRouteConnectionInner object