fix grpc MethodDescriptor fullMethodName problem

Fixes gh-2910

docs/src/main/asciidoc/spring-cloud-gateway.adoc

@@ -1849,7 +1849,7 @@ src/main/resources/proto/hello.proto
 
 * `protoFile` Proto definition file.
 
-* `service` Fully qualified name of the service that will handle the request.
+* `service` Short name of the service that will handle the request.
 
 * `method` Method name in the service that will handle the request.
 
@@ -1887,12 +1887,12 @@ spring:
               args:
                 protoDescriptor: file:proto/hello.pb
                 protoFile: file:proto/hello.proto
-                service: com.example.grpcserver.hello.HelloService
+                service: HelloService
                 method: hello
 
 ----
 
-When a request is made through the gateway to `/json/hello` the request will be transformed using the definition provided in `hello.proto`, sent to `com.example.grpcserver.hello.HelloService/hello`, and transform the response back to JSON.
+When a request is made through the gateway to `/json/hello` the request will be transformed using the definition provided in `hello.proto`, sent to `HelloService/hello`, and transform the response back to JSON.
 
 By default, it will create a `NettyChannel` using the default `TrustManagerFactory`. However, this `TrustManager` can be customized by creating a bean of type `GrpcSslConfigurer`:
 

spring-cloud-gateway-integration-tests/grpc/src/main/proto/hello.proto

@@ -1,6 +1,7 @@
 syntax = "proto3";
 option java_multiple_files = true;
 option java_package = "org.springframework.cloud.gateway.tests.grpc";
+package org.springframework.cloud.gateway.tests.grpc;
 
 message HelloRequest {
   optional string firstName = 1;

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/factory/JsonToGrpcGatewayFilterFactory.java

@@ -192,9 +192,12 @@ public class JsonToGrpcGatewayFilterFactory
 				descriptor = DescriptorProtos.FileDescriptorProto.parseFrom(descriptorFile.getInputStream())
 						.getDescriptorForType();
 
-				Descriptors.Descriptor outputType = getOutputTypeDescriptor(config, descriptorFile.getInputStream());
+				Descriptors.MethodDescriptor methodDescriptor = getMethodDescriptor(config,
+						descriptorFile.getInputStream());
+				Descriptors.ServiceDescriptor serviceDescriptor = methodDescriptor.getService();
+				Descriptors.Descriptor outputType = methodDescriptor.getOutputType();
 
-				clientCall = createClientCallForType(config, outputType);
+				clientCall = createClientCallForType(config, serviceDescriptor, outputType);
 
 				ProtobufSchema schema = ProtobufSchemaLoader.std.load(protoFile.getInputStream());
 				ProtobufSchema responseType = schema.withRootType(outputType.getName());
@@ -220,18 +223,19 @@ public class JsonToGrpcGatewayFilterFactory
 		}
 
 		private ClientCall<DynamicMessage, DynamicMessage> createClientCallForType(Config config,
-				Descriptors.Descriptor outputType) {
+				Descriptors.ServiceDescriptor serviceDescriptor, Descriptors.Descriptor outputType) {
 			MethodDescriptor.Marshaller<DynamicMessage> marshaller = ProtoUtils
 					.marshaller(DynamicMessage.newBuilder(outputType).build());
 			MethodDescriptor<DynamicMessage, DynamicMessage> methodDescriptor = MethodDescriptor
 					.<DynamicMessage, DynamicMessage>newBuilder().setType(MethodDescriptor.MethodType.UNKNOWN)
-					.setFullMethodName(MethodDescriptor.generateFullMethodName(config.getService(), config.getMethod()))
+					.setFullMethodName(MethodDescriptor.generateFullMethodName(serviceDescriptor.getFullName(),
+							config.getMethod()))
 					.setRequestMarshaller(marshaller).setResponseMarshaller(marshaller).build();
 			Channel channel = createChannel();
 			return channel.newCall(methodDescriptor, CallOptions.DEFAULT);
 		}
 
-		private Descriptors.Descriptor getOutputTypeDescriptor(Config config, InputStream descriptorFile)
+		private Descriptors.MethodDescriptor getMethodDescriptor(Config config, InputStream descriptorFile)
 				throws IOException, Descriptors.DescriptorValidationException {
 			DescriptorProtos.FileDescriptorSet fileDescriptorSet = DescriptorProtos.FileDescriptorSet
 					.parseFrom(descriptorFile);
@@ -239,11 +243,15 @@ public class JsonToGrpcGatewayFilterFactory
 			Descriptors.FileDescriptor fileDescriptor = Descriptors.FileDescriptor.buildFrom(fileProto,
 					new Descriptors.FileDescriptor[0]);
 
-			List<Descriptors.MethodDescriptor> methods = fileDescriptor.findServiceByName(config.getService())
-					.getMethods();
+			Descriptors.ServiceDescriptor serviceDescriptor = fileDescriptor.findServiceByName(config.getService());
+			if (serviceDescriptor == null) {
+				throw new NoSuchElementException("No Service found");
+			}
+
+			List<Descriptors.MethodDescriptor> methods = serviceDescriptor.getMethods();
 
 			return methods.stream().filter(method -> method.getName().equals(config.getMethod())).findFirst()
-					.orElseThrow(() -> new NoSuchElementException("No Method found")).getOutputType();
+					.orElseThrow(() -> new NoSuchElementException("No Method found"));
 		}
 
 		private ManagedChannel createChannel() {