Support returning multiple streaming responses for a unary gRPC request

build.gradle

@@ -110,6 +110,7 @@ dependencies {
   testFixturesApi "org.hamcrest:hamcrest-core:3.0"
   testFixturesApi "org.hamcrest:hamcrest-library:3.0"
   testFixturesApi 'org.awaitility:awaitility:4.2.2'
+  testFixturesApi 'org.slf4j:slf4j-simple:2.0.16'
 
   testFixturesApi "io.grpc:grpc-okhttp"
 

src/main/java/org/wiremock/grpc/dsl/WireMockGrpc.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2023-2024 Thomas Akehurst
+ * Copyright (C) 2023-2025 Thomas Akehurst
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,6 +20,8 @@
 import com.github.tomakehurst.wiremock.common.Json;
 import com.github.tomakehurst.wiremock.matching.StringValuePattern;
 import com.google.protobuf.MessageOrBuilder;
+import java.util.List;
+import java.util.stream.Collectors;
 import org.wiremock.annotations.Beta;
 import org.wiremock.grpc.internal.JsonMessageUtils;
 
@@ -50,6 +52,17 @@ public static GrpcResponseDefinitionBuilder message(MessageOrBuilder messageOrBu
     return new GrpcResponseDefinitionBuilder(Status.OK).fromJson(json);
   }
 
+  public static GrpcResponseDefinitionBuilder messages(
+      List<MessageOrBuilder> messageOrBuilderList) {
+    final String json =
+        "[\n"
+            + messageOrBuilderList.stream()
+                .map(JsonMessageUtils::toJson)
+                .collect(Collectors.joining(",\n"))
+            + "\n]";
+    return new GrpcResponseDefinitionBuilder(Status.OK).fromJson(json);
+  }
+
   public static GrpcResponseDefinitionBuilder messageAsAny(MessageOrBuilder messageOrBuilder) {
     final String initialJson = JsonMessageUtils.toJson(messageOrBuilder);
     final ObjectNode jsonObject = Json.read(initialJson, ObjectNode.class);

src/main/java/org/wiremock/grpc/internal/UnaryServerCallHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2023-2024 Thomas Akehurst
+ * Copyright (C) 2023-2025 Thomas Akehurst
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,9 @@
 import static org.wiremock.grpc.dsl.GrpcResponseDefinitionBuilder.GRPC_STATUS_REASON;
 import static org.wiremock.grpc.internal.Delays.delayIfRequired;
 
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.MappingIterator;
+import com.fasterxml.jackson.databind.ObjectMapper;
 import com.github.tomakehurst.wiremock.common.Pair;
 import com.github.tomakehurst.wiremock.http.HttpHeader;
 import com.github.tomakehurst.wiremock.http.StubRequestHandler;
@@ -28,11 +31,14 @@
 import io.grpc.Status;
 import io.grpc.stub.ServerCalls;
 import io.grpc.stub.StreamObserver;
+import java.io.IOException;
 import org.wiremock.grpc.dsl.WireMockGrpc;
 
 public class UnaryServerCallHandler extends BaseCallHandler
     implements ServerCalls.UnaryMethod<DynamicMessage, DynamicMessage> {
 
+  private final ObjectMapper objectMapper = new ObjectMapper();
+
   public UnaryServerCallHandler(
       StubRequestHandler stubRequestHandler,
       Descriptors.ServiceDescriptor serviceDescriptor,
@@ -85,12 +91,26 @@ public void invoke(DynamicMessage request, StreamObserver<DynamicMessage> respon
             return;
           }
 
-          DynamicMessage.Builder messageBuilder =
-              DynamicMessage.newBuilder(methodDescriptor.getOutputType());
+          try (MappingIterator<JsonNode> iterator =
+              objectMapper.readerFor(JsonNode.class).readValues(resp.getBody())) {
+
+            while (iterator.hasNext()) {
+              JsonNode node = iterator.next();
+
+              final DynamicMessage.Builder messageBuilder =
+                  DynamicMessage.newBuilder(methodDescriptor.getOutputType());
+              final DynamicMessage response =
+                  jsonMessageConverter.toMessage(node.toString(), messageBuilder);
 
-          final DynamicMessage response =
-              jsonMessageConverter.toMessage(resp.getBodyAsString(), messageBuilder);
-          responseObserver.onNext(response);
+              responseObserver.onNext(response);
+            }
+          } catch (IOException e) {
+            responseObserver.onError(
+                Status.INTERNAL
+                    .withDescription("Error parsing response")
+                    .withCause(e)
+                    .asRuntimeException());
+          }
           responseObserver.onCompleted();
         },
         ServeEvent.of(wireMockRequest));

src/test/java/org/wiremock/grpc/GrpcAcceptanceTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2023-2024 Thomas Akehurst
+ * Copyright (C) 2023-2025 Thomas Akehurst
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.greaterThanOrEqualTo;
 import static org.hamcrest.Matchers.hasItem;
+import static org.hamcrest.Matchers.hasItems;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.iterableWithSize;
@@ -39,6 +40,7 @@
 import static org.wiremock.grpc.dsl.WireMockGrpc.jsonTemplate;
 import static org.wiremock.grpc.dsl.WireMockGrpc.message;
 import static org.wiremock.grpc.dsl.WireMockGrpc.messageAsAny;
+import static org.wiremock.grpc.dsl.WireMockGrpc.messages;
 import static org.wiremock.grpc.dsl.WireMockGrpc.method;
 
 import com.example.grpc.AnotherGreetingServiceGrpc;
@@ -282,14 +284,27 @@ void throwsReturnedErrorFromStreamingClientCallWhenServerOnlyReturnsAHttpStatus(
   }
 
   @Test
-  void returnsStreamedResponseToUnaryRequest() {
+  void returnsStreamedResponseToUnaryRequestWithSingleItem() {
     mockGreetingService.stubFor(
         method("oneGreetingManyReplies")
             .willReturn(message(HelloResponse.newBuilder().setGreeting("Hi Tom"))));
 
     assertThat(greetingsClient.oneGreetingManyReplies("Tom"), hasItem("Hi Tom"));
   }
 
+  @Test
+  void returnsStreamedResponseToUnaryRequest() {
+    mockGreetingService.stubFor(
+        method("oneGreetingManyReplies")
+            .willReturn(
+                messages(
+                    List.of(
+                        HelloResponse.newBuilder().setGreeting("Hi Tom"),
+                        HelloResponse.newBuilder().setGreeting("Hi Tom again")))));
+
+    assertThat(greetingsClient.oneGreetingManyReplies("Tom"), hasItems("Hi Tom", "Hi Tom again"));
+  }
+
   @Test
   void returnsResponseWithImportedType() {
     mockGreetingService.stubFor(
@@ -337,7 +352,7 @@ void networkFault() {
 
     Exception exception =
         assertThrows(StatusRuntimeException.class, () -> greetingsClient.greet("Alan"));
-    assertThat(exception.getMessage(), startsWith("UNKNOWN"));
+    assertThat(exception.getMessage(), startsWith("CANCELLED"));
   }
 
   @Test

wiremock-grpc-extension-jetty12/src/test/java/org/wiremock/grpc/Jetty12GrpcAcceptanceTest.java

@@ -26,6 +26,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.greaterThanOrEqualTo;
 import static org.hamcrest.Matchers.hasItem;
+import static org.hamcrest.Matchers.hasItems;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.iterableWithSize;
@@ -39,6 +40,7 @@
 import static org.wiremock.grpc.dsl.WireMockGrpc.jsonTemplate;
 import static org.wiremock.grpc.dsl.WireMockGrpc.message;
 import static org.wiremock.grpc.dsl.WireMockGrpc.messageAsAny;
+import static org.wiremock.grpc.dsl.WireMockGrpc.messages;
 import static org.wiremock.grpc.dsl.WireMockGrpc.method;
 
 import com.example.grpc.AnotherGreetingServiceGrpc;
@@ -283,14 +285,27 @@ void throwsReturnedErrorFromStreamingClientCallWhenServerOnlyReturnsAHttpStatus(
   }
 
   @Test
-  void returnsStreamedResponseToUnaryRequest() {
+  void returnsStreamedResponseToUnaryRequestWithSingleItem() {
     mockGreetingService.stubFor(
         method("oneGreetingManyReplies")
             .willReturn(message(HelloResponse.newBuilder().setGreeting("Hi Tom"))));
 
     assertThat(greetingsClient.oneGreetingManyReplies("Tom"), hasItem("Hi Tom"));
   }
 
+  @Test
+  void returnsStreamedResponseToUnaryRequest() {
+    mockGreetingService.stubFor(
+        method("oneGreetingManyReplies")
+            .willReturn(
+                messages(
+                    List.of(
+                        HelloResponse.newBuilder().setGreeting("Hi Tom"),
+                        HelloResponse.newBuilder().setGreeting("Hi Tom again")))));
+
+    assertThat(greetingsClient.oneGreetingManyReplies("Tom"), hasItems("Hi Tom", "Hi Tom again"));
+  }
+
   @Test
   void returnsResponseWithImportedType() {
     mockGreetingService.stubFor(
@@ -338,7 +353,7 @@ void networkFault() {
 
     Exception exception =
         assertThrows(StatusRuntimeException.class, () -> greetingsClient.greet("Alan"));
-    assertThat(exception.getMessage(), startsWith("UNKNOWN"));
+    assertThat(exception.getMessage(), startsWith("CANCELLED"));
   }
 
   @Test