Hi guys, I have the following scenario: I have the following folder structure: -- wiremock --- src/main/java/org/company/wiremock/CustomHostTransformer.java ---src/main/resources/META-INF/services/com.github.tomakehurst.wiremock.extension.ResponseTransformerV2 --- pom.xml --- Dockerfile pom.xml looks like:

<project xmlns="<http://maven.apache.org/POM/4.0.0>"
  xmlns:xsi="<http://www.w3.org/2001/XMLSchema-instance>"
  xsi:schemaLocation="<http://maven.apache.org/POM/4.0.0> <http://maven.apache.org/xsd/maven-4.0.0.xsd>">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.company</groupId>
  <artifactId>wiremock-transformer</artifactId>
  <version>1.0</version>

  <properties>
    <java.version>21</java.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.wiremock</groupId>
      <artifactId>wiremock-standalone</artifactId>
      <version>3.9.1</version>
    </dependency>
  </dependencies>
</project>

The docker file looks like:

# -- Maven 'builder' stage
FROM maven:3.9.6-eclipse-temurin-21 AS builder
WORKDIR /home/builder
COPY pom.xml .
COPY src ./src

# Run Maven to build and package the custom transformer JAR
RUN mvn clean package

# -- WireMock 'runner' stage
FROM wiremock/wiremock:3.9.1 AS runner
WORKDIR /home/wiremock

# Copy the transformer JAR from the Maven builder stage to the WireMock extensions directory
COPY --from=builder /home/builder/target/wiremock-transformer-1.0.jar /home/wiremock/extensions/

# tmp
RUN apt-get update && apt-get install -y zip

# Set up WireMock to use the transformer
ENTRYPOINT ["/docker-entrypoint.sh", "--verbose", "--async-response-enabled=true", "--container-threads=1000", "--async-response-threads=500", "--disable-request-logging", "--extensions", "org.company.wiremock.CustomHostTransformer"]

My CustomHostTransformer.java looks like:

package org.company.wiremock;

import com.github.tomakehurst.wiremock.extension.ResponseTransformerV2;
import com.github.tomakehurst.wiremock.http.Response;
import com.github.tomakehurst.wiremock.stubbing.ServeEvent;

public class CustomHostTransformer implements ResponseTransformerV2 {
  
  @Override
  public String getName() {
    return "custom-host-transformer";
  }

  @Override
  public Response transform(Response response, ServeEvent serveEvent) {
    System.out.println("CustomHostTransformer loaded!");
    return response;
  }
}

I have also added a service in META-INF/services/com.github.tomakehurst.wiremock.extension.ResponseTransformerV2. The content is:

org.company.wiremock.CustomHostTransformer

I keep getting the following error when I try to run it:

2024-09-12 13:59:55.187 Verbose logging enabled
Exception in thread "main" java.lang.ClassNotFoundException: org.company.wiremock.CustomHostTransformer
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown Source)
	at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Unknown Source)
	at com.github.tomakehurst.wiremock.extension.Extensions.loadClass(Extensions.java:223)
	at java.base/java.util.stream.ReferencePipeline$3$1.accept(Unknown Source)
	at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(Unknown Source)
	at java.base/java.util.stream.AbstractPipeline.copyInto(Unknown Source)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
	at java.base/java.util.stream.StreamSpliterators$WrappingSpliterator.forEachRemaining(Unknown Source)
	at java.base/java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Unknown Source)
	at java.base/java.util.stream.AbstractPipeline.copyInto(Unknown Source)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
	at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(Unknown Source)
	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(Unknown Source)
	at java.base/java.util.stream.AbstractPipeline.evaluate(Unknown Source)
	at java.base/java.util.stream.ReferencePipeline.forEach(Unknown Source)
	at com.github.tomakehurst.wiremock.extension.Extensions.load(Extensions.java:80)
	at com.github.tomakehurst.wiremock.core.WireMockApp.<init>(WireMockApp.java:108)
	at com.github.tomakehurst.wiremock.WireMockServer.<init>(WireMockServer.java:74)
	at com.github.tomakehurst.wiremock.standalone.WireMockServerRunner.run(WireMockServerRunner.java:71)
	at wiremock.Run.main(Run.java:23)

Any insights? I also tried to log into the shell to see if all the files are present, see:

❯ docker run --rm -it --entrypoint sh wiremock-with-custom-transformer
# ls
extensions  __files  mappings
# cd extensions
# ls
wiremock-transformer-1.0.jar
# unzip wiremock-transformer-1.0.jar
Archive:  wiremock-transformer-1.0.jar
   creating: META-INF/
  inflating: META-INF/MANIFEST.MF
   creating: org/
   creating: org/company/
   creating: org/company/wiremock/
   creating: META-INF/services/
   creating: META-INF/maven/
   creating: META-INF/maven/org.company.wiremock/
   creating: META-INF/maven/org.company.wiremock/wiremock-transformer/
  inflating: org/company/wiremock/CustomHostTransformer.class
  inflating: META-INF/services/com.github.tomakehurst.wiremock.extension.ResponseTransformerV2
  inflating: META-INF/maven/org.company.wiremock/wiremock-transformer/pom.xml
  inflating: META-INF/maven/org.company.wiremock/wiremock-transformer/pom.properties

Since you’ve added the service metadata to the extension you should drop the

--extensions

CLI parameter otherwise it’ll try to load it twice.

I tried that, but it then does not pick the extension 😞

Sounds like either the extension isn’t landing in the extensions directory, or for some reason the command line has changed and that directory isn’t on the classpath at startup