Using the Pluggable Architecture

import java.io.File;
import java.util.Collection;

/**
 * Converter to be used to convert FROM {@link File} TO {@link Contract} and from
 * {@link Contract} to {@code T}.
 *
 * @param <T> - type to which we want to convert the contract
 * @author Marcin Grzejszczak
 * @since 1.1.0
 */
public interface ContractConverter<T> extends ContractStorer<T>, ContractReader<T> {

	/**
	 * Should this file be accepted by the converter. Can use the file extension to check
	 * if the conversion is possible.
	 * @param file - file to be considered for conversion
	 * @return - {@code true} if the given implementation can convert the file
	 */
	boolean isAccepted(File file);

	/**
	 * Converts the given {@link File} to its {@link Contract} representation.
	 * @param file - file to convert
	 * @return - {@link Contract} representation of the file
	 */
	Collection<Contract> convertFrom(File file);

	/**
	 * Converts the given {@link Contract} to a {@link T} representation.
	 * @param contract - the parsed contract
	 * @return - {@link T} the type to which we do the conversion
	 */
	T convertTo(Collection<Contract> contract);

}

org.springframework.cloud.contract.spec.ContractConverter=\
org.springframework.cloud.contract.verifier.converter.YamlContractConverter

import java.nio.file.Path;
import java.util.Collection;

import org.springframework.cloud.contract.verifier.config.ContractVerifierConfigProperties;
import org.springframework.cloud.contract.verifier.file.ContractMetadata;

/**
 * Builds a single test.
 *
 * @since 1.1.0
 */
public interface SingleTestGenerator {

	/**
	 * Creates contents of a single test class in which all test scenarios from the
	 * contract metadata should be placed.
	 * @param properties - properties passed to the plugin
	 * @param listOfFiles - list of parsed contracts with additional metadata
	 * @param generatedClassData - information about the generated class
	 * @param includedDirectoryRelativePath - relative path to the included directory
	 * @return contents of a single test class
	 */
	String buildClass(ContractVerifierConfigProperties properties, Collection<ContractMetadata> listOfFiles,
			String includedDirectoryRelativePath, GeneratedClassData generatedClassData);

	class GeneratedClassData {

		public final String className;

		public final String classPackage;

		public final Path testClassPath;

		public GeneratedClassData(String className, String classPackage, Path testClassPath) {
			this.className = className;
			this.classPackage = classPackage;
			this.testClassPath = testClassPath;
		}

	}

}

org.springframework.cloud.contract.verifier.builder.SingleTestGenerator=/
com.example.MyGenerator

import java.io.File;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import org.springframework.cloud.contract.spec.Contract;
import org.springframework.cloud.contract.verifier.file.ContractMetadata;

/**
 * Converts contracts into their stub representation.
 *
 * @param <T> - type of stub mapping
 * @since 1.1.0
 */
public interface StubGenerator<T> {

	/**
	 * @param mapping - potential stub mapping mapping
	 * @return {@code true} if this converter could have generated this mapping stub.
	 */
	default boolean canReadStubMapping(File mapping) {
		return mapping.getName().endsWith(fileExtension());
	}

	/**
	 * @param rootName - root name of the contract
	 * @param content - metadata of the contract
	 * @return the collection of converted contracts into stubs. One contract can result
	 * in multiple stubs.
	 */
	Map<Contract, String> convertContents(String rootName, ContractMetadata content);

	/**
	 * Post process a generated stub mapping.
	 * @param stubMapping - mapping of a stub
	 * @param contract - contract for which stub was generated
	 * @return the converted stub mapping
	 */
	default T postProcessStubMapping(T stubMapping, Contract contract) {
		List<StubPostProcessor> processors = StubPostProcessor.PROCESSORS.stream().filter(p -> p.isApplicable(contract))
				.collect(Collectors.toList());
		if (processors.isEmpty()) {
			return defaultStubMappingPostProcessing(stubMapping, contract);
		}
		T stub = stubMapping;
		for (StubPostProcessor processor : processors) {
			stub = (T) processor.postProcess(stub, contract);
		}
		return stub;
	}

	/**
	 * Stub mapping to chose when no post processors where found on the classpath.
	 * @param stubMapping - mapping of a stub
	 * @param contract - contract for which stub was generated
	 * @return the converted stub mapping
	 */
	default T defaultStubMappingPostProcessing(T stubMapping, Contract contract) {
		return stubMapping;
	}

	/**
	 * @param inputFileName - name of the input file
	 * @return the name of the converted stub file. If you have multiple contracts in a
	 * single file then a prefix will be added to the generated file. If you provide the
	 * {@link Contract#getName} field then that field will override the generated file
	 * name.
	 *
	 * Example: name of file with 2 contracts is {@code foo.groovy}, it will be converted
	 * by the implementation to {@code foo.json}. The recursive file converter will create
	 * two files {@code 0_foo.json} and {@code 1_foo.json}
	 */
	String generateOutputFileNameForInput(String inputFileName);

	/**
	 * Describes the file extension of the generated mapping that this stub generator can
	 * handle.
	 * @return string describing the file extension
	 */
	default String fileExtension() {
		return ".json";
	}

}

# Stub converters
org.springframework.cloud.contract.verifier.converter.StubGenerator=\
org.springframework.cloud.contract.verifier.wiremock.DslToWireMockClientConverter

import com.github.dreamhead.moco.bootstrap.arg.HttpArgs
import com.github.dreamhead.moco.runner.JsonRunner
import com.github.dreamhead.moco.runner.RunnerSetting
import groovy.transform.CompileStatic
import groovy.util.logging.Commons

import org.springframework.cloud.contract.stubrunner.HttpServerStub
import org.springframework.cloud.contract.stubrunner.HttpServerStubConfiguration

@Commons
@CompileStatic
class MocoHttpServerStub implements HttpServerStub {

	private boolean started
	private JsonRunner runner
	private int port

	@Override
	int port() {
		if (!isRunning()) {
			return -1
		}
		return port
	}

	@Override
	boolean isRunning() {
		return started
	}

	@Override
	HttpServerStub start(HttpServerStubConfiguration configuration) {
		this.port = configuration.port
		return this
	}

	@Override
	HttpServerStub stop() {
		if (!isRunning()) {
			return this
		}
		this.runner.stop()
		return this
	}

	@Override
	HttpServerStub registerMappings(Collection<File> stubFiles) {
		List<RunnerSetting> settings = stubFiles.findAll { it.name.endsWith("json") }
			.collect {
			log.info("Trying to parse [${it.name}]")
			try {
				return RunnerSetting.aRunnerSetting().addStream(it.newInputStream()).
					build()
			}
			catch (Exception e) {
				log.warn("Exception occurred while trying to parse file [${it.name}]", e)
				return null
			}
		}.findAll { it }
		this.runner = JsonRunner.newJsonRunnerWithSetting(settings,
			HttpArgs.httpArgs().withPort(this.port).build())
		this.runner.run()
		this.started = true
		return this
	}

	@Override
	String registeredMappings() {
		return ""
	}

	@Override
	boolean isAccepted(File file) {
		return file.name.endsWith(".json")
	}
}

org.springframework.cloud.contract.stubrunner.HttpServerStub=\
org.springframework.cloud.contract.stubrunner.provider.moco.MocoHttpServerStub

class CustomStubDownloaderBuilder implements StubDownloaderBuilder {

	@Override
	public StubDownloader build(final StubRunnerOptions stubRunnerOptions) {
		return new StubDownloader() {
			@Override
			public Map.Entry<StubConfiguration, File> downloadAndUnpackStubJar(
					StubConfiguration config) {
				File unpackedStubs = retrieveStubs();
				return new AbstractMap.SimpleEntry<>(
						new StubConfiguration(config.getGroupId(), config.getArtifactId(), version,
								config.getClassifier()), unpackedStubs);
			}

			File retrieveStubs() {
			    // here goes your custom logic to provide a folder where all the stubs reside
			}
		}
	}
}

# Example of a custom Stub Downloader Provider
org.springframework.cloud.contract.stubrunner.StubDownloaderBuilder=\
com.example.CustomStubDownloaderBuilder