code: public Observable<VnetGatewayInner> getVnetGatewayAsync(String resourceGroupName, String name, String vnetName, String gatewayName) {
          return getVnetGatewayWithServiceResponseAsync(resourceGroupName, name, vnetName, gatewayName).map(new Func1<ServiceResponse<VnetGatewayInner>, VnetGatewayInner>() {
              @Override
              public VnetGatewayInner call(ServiceResponse<VnetGatewayInner> response) {
                  return response.body();
              }
          });
      }
docs: Get a Virtual Network gateway.
  Get a Virtual Network gateway.
  
  @param resourceGroupName Name of the resource group to which the resource belongs.
  @param name Name of the App Service plan.
  @param vnetName Name of the Virtual Network.
  @param gatewayName Name of the gateway. Only the 'primary' gateway is supported.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the VnetGatewayInner object