Hey folks, I’m trying to run WireMock in Docker with the gRPC Extension, but I’m not having any luck. I followed the docs for running WireMock with extensions in Docker by doing the following: 1. Downloading the latest JAR of the extension and moving it to the

./extensions/

directory. 2. Running the following:

docker run -it --rm \
  -p 8080:8080      \
  --name wiremock   \
  -v "${PWD}/extensions:/var/wiremock/extensions" \
  wiremock/wiremock:3.3.1                         \
  --extensions "org.wiremock.grpc.GrpcExtensionFactory"

However, this results in the error:

Exception in thread "main" java.lang.ClassCastException: class org.wiremock.grpc.GrpcExtensionFactory cannot be cast to class com.github.tomakehurst.wiremock.extension.Extension (org.wiremock.grpc.GrpcExtensionFactory and com.github.tomakehurst.wiremock.extension.Extension are in unnamed module of loader 'app')

Inspecting the `GrpcExtensionFactory` class, I see that it doesn’t extend

Extension

, but instead extends

ExtensionFactory

and creates

Extension

instances. Here’s where I hit a wall though, because I can’t find any documentation that explains how to run WireMock with `ExtensionFactory`s. Can someone shed some light for me?

Hi Dan, the gRPC extension uses the new classpath scanning capability so you need to make sure that a) the gRPC JAR is on the classpath, and b) don’t set the

--extensions

parameter at all as this will attempt to double load the extension.