In this section, we describe how to customize various parts of Spring Cloud Contract.
1. DSL Customization
This section is valid only for the Groovy DSL |
You can customize the Spring Cloud Contract Verifier by extending the DSL, as shown in the remainder of this section.
1.1. Extending the DSL
You can provide your own functions to the DSL. The key requirement for this feature is to maintain the static compatibility. Later in this chapter, you can see examples of:
-
Creating a JAR with reusable classes.
-
Referencing of these classes in the DSLs.
You can find the full example here.
1.2. Common JAR
The following examples show three classes that can be reused in the DSLs.
PatternUtils
contains functions used by both the consumer and the producer.
The following listing shows the PatternUtils
class:
package com.example;
import java.util.regex.Pattern;
/**
* If you want to use {@link Pattern} directly in your tests
* then you can create a class resembling this one. It can
* contain all the {@link Pattern} you want to use in the DSL.
*
* <pre>
* {@code
* request {
* body(
* [ age: $(c(PatternUtils.oldEnough()))]
* )
* }
* </pre>
*
* Notice that we're using both {@code $()} for dynamic values
* and {@code c()} for the consumer side.
*
* @author Marcin Grzejszczak
*/
public class PatternUtils {
public static String tooYoung() {
return "[0-1][0-9]";
}
public static Pattern oldEnough() {
return Pattern.compile("[2-9][0-9]");
}
/**
* Makes little sense but it's just an example ;)
*/
public static Pattern ok() {
return Pattern.compile("OK");
}
}
ConsumerUtils
contains functions used by the consumer.
The following listing shows the ConsumerUtils
class:
package com.example;
import org.springframework.cloud.contract.spec.internal.ClientDslProperty;
/**
* DSL Properties passed to the DSL from the consumer's perspective.
* That means that on the input side {@code Request} for HTTP
* or {@code Input} for messaging you can have a regular expression.
* On the {@code Response} for HTTP or {@code Output} for messaging
* you have to have a concrete value.
*
* @author Marcin Grzejszczak
*/
public class ConsumerUtils {
/**
* Consumer side property. By using the {@link ClientDslProperty}
* you can omit most of boilerplate code from the perspective
* of dynamic values. Example
*
* <pre>
* {@code
* request {
* body(
* [ age: $(ConsumerUtils.oldEnough())]
* )
* }
* </pre>
*
* That way it's in the implementation that we decide what value we will pass to the consumer
* and which one to the producer.
*
* @author Marcin Grzejszczak
*/
public static ClientDslProperty oldEnough() {
// this example is not the best one and
// theoretically you could just pass the regex instead of `ServerDslProperty` but
// it's just to show some new tricks :)
return new ClientDslProperty(PatternUtils.oldEnough(), 40);
}
}
ProducerUtils
contains functions used by the producer.
The following listing shows the ProducerUtils
class:
package com.example;
import org.springframework.cloud.contract.spec.internal.ServerDslProperty;
/**
* DSL Properties passed to the DSL from the producer's perspective.
* That means that on the input side {@code Request} for HTTP
* or {@code Input} for messaging you have to have a concrete value.
* On the {@code Response} for HTTP or {@code Output} for messaging
* you can have a regular expression.
*
* @author Marcin Grzejszczak
*/
public class ProducerUtils {
/**
* Producer side property. By using the {@link ProducerUtils}
* you can omit most of boilerplate code from the perspective
* of dynamic values. Example
*
* <pre>
* {@code
* response {
* body(
* [ status: $(ProducerUtils.ok())]
* )
* }
* </pre>
*
* That way it's in the implementation that we decide what value we will pass to the consumer
* and which one to the producer.
*/
public static ServerDslProperty ok() {
// this example is not the best one and
// theoretically you could just pass the regex instead of `ServerDslProperty` but
// it's just to show some new tricks :)
return new ServerDslProperty( PatternUtils.ok(), "OK");
}
}
1.3. Adding a Test Dependency in the Project’s Dependencies
To add a test dependency in the project’s dependencies, you must first add the common jar dependency as a test dependency. Because your contracts files are available on the test resources path, the common jar classes automatically become visible in your Groovy files. The following examples show how to test the dependency:
1.4. Adding a Test Dependency in the Plugin’s Dependencies
Now, you must add the dependency for the plugin to reuse at runtime, as the following example shows:
1.5. Referencing Classes in DSLs
You can now reference your classes in your DSL, as the following example shows:
package contracts.beer.rest
import com.example.ConsumerUtils
import com.example.ProducerUtils
import org.springframework.cloud.contract.spec.Contract
Contract.make {
description("""
Represents a successful scenario of getting a beer
```
given:
client is old enough
when:
he applies for a beer
then:
we'll grant him the beer
```
""")
request {
method 'POST'
url '/check'
body(
age: $(ConsumerUtils.oldEnough())
)
headers {
contentType(applicationJson())
}
}
response {
status 200
body("""
{
"status": "${value(ProducerUtils.ok())}"
}
""")
headers {
contentType(applicationJson())
}
}
}
You can set the Spring Cloud Contract plugin up by setting convertToYaml to
true . That way, you do NOT have to add the dependency with the extended functionality
to the consumer side, since the consumer side uses YAML contracts instead of Groovy contracts.
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2. WireMock Customization
In this section, we show how to customize the way you work with WireMock.
2.1. Registering Your Own WireMock Extension
WireMock lets you register custom extensions. By default, Spring Cloud Contract registers
the transformer, which lets you reference a request from a response. If you want to
provide your own extensions, you can register an implementation of the
org.springframework.cloud.contract.verifier.dsl.wiremock.WireMockExtensions
interface.
Since we use the spring.factories
extension approach, you can create an entry similar to
the following in the META-INF/spring.factories
file:
org.springframework.cloud.contract.verifier.dsl.wiremock.WireMockExtensions=\
org.springframework.cloud.contract.stubrunner.provider.wiremock.TestWireMockExtensions
org.springframework.cloud.contract.spec.ContractConverter=\
org.springframework.cloud.contract.stubrunner.TestCustomYamlContractConverter
The following example shows a custom extension:
/*
* Copyright 2013-2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.cloud.contract.verifier.dsl.wiremock
import com.github.tomakehurst.wiremock.extension.Extension
/**
* Extension that registers the default transformer and the custom one
*/
class TestWireMockExtensions implements WireMockExtensions {
@Override
List<Extension> extensions() {
return [
new DefaultResponseTransformer(),
new CustomExtension()
]
}
}
class CustomExtension implements Extension {
@Override
String getName() {
return "foo-transformer"
}
}
If you want the transformation to be applied only for a mapping that explicitly
requires it, override the applyGlobally() method and set it to false .
|
2.2. Customization of WireMock Configuration
You can register a bean of type org.springframework.cloud.contract.wiremock.WireMockConfigurationCustomizer
to customize the WireMock configuration (for example, to add custom transformers).
The following example shows how to do so:
@Bean
WireMockConfigurationCustomizer optionsCustomizer() {
return new WireMockConfigurationCustomizer() {
@Override
public void customize(WireMockConfiguration options) {
// perform your customization here
}
};
}
2.3. Customization of WireMock via Metadata
With version 3.0.0 you’re able to set metadata
in your contracts. If you set an entry with key equal to wiremock
and the value
will be a valid WireMock’s StubMapping
JSON / map or an actual StubMapping
object, Spring Cloud Contract will patch the generated
stub with part of your customization. Let’s look at the following example
name: "should count all frauds"
request:
method: GET
url: /yamlfrauds
response:
status: 200
body:
count: 200
headers:
Content-Type: application/json
metadata:
wiremock:
stubMapping: >
{
"response" : {
"fixedDelayMilliseconds": 2000
}
}
In the metadata
section we’ve set an entry with key wiremock
and its value is a JSON StubMapping
that sets a delay in the generated stub. Such code allowed us to get the following merged WireMock JSON stub.
{
"id" : "ebae49e2-a2a3-490c-a57f-ba28e26b81ea",
"request" : {
"url" : "/yamlfrauds",
"method" : "GET"
},
"response" : {
"status" : 200,
"body" : "{\"count\":200}",
"headers" : {
"Content-Type" : "application/json"
},
"fixedDelayMilliseconds" : 2000,
"transformers" : [ "response-template" ]
},
"uuid" : "ebae49e2-a2a3-490c-a57f-ba28e26b81ea"
}
The current implementation allows to manipulate only the stub side (we don’t change the generated test). Also, what does not get changed are the whole request and body and headers of the response.
2.3.1. Customization of WireMock via Metadata and a Custom Processor
If you want to apply a custom WireMock StubMapping
post processing, you can under META-INF/spring.factories
under the
org.springframework.cloud.contract.verifier.converter.StubProcessor
key register your own implementation of a stub processor. For your convenience we’ve created an interface called org.springframework.cloud.contract.verifier.wiremock.WireMockStubPostProcessor
that is dedicated to WireMock.
You’ll have to implement methods to inform Spring Cloud Contract whether the post processor is applicable for a given contract and how should the post processing look like.
On the consumer side, when using Stub Runner, remember to pass the custom HttpServerStubConfigurer implementation (e.g. the one that extends WireMockHttpServerStubConfigurer ) where you’ll register a custom extension of your choosing. If you don’t do so, even you have a custom WireMock extension on the classpath, WireMock will not notice it, won’t apply it and will print out a warning statement that the given extension was not found.
|
3. Using the Pluggable Architecture
You may encounter cases where your contracts have been defined in other formats, such as YAML, RAML, or PACT. In those cases, you still want to benefit from the automatic generation of tests and stubs. You can add your own implementation for generating both tests and stubs. Also, you can customize the way tests are generated (for example, you can generate tests for other languages) and the way stubs are generated (for example, you can generate stubs for other HTTP server implementations).
3.1. Custom Contract Converter
The ContractConverter
interface lets you register your own implementation of a contract
structure converter. The following code listing shows the ContractConverter
interface:
package org.springframework.cloud.contract.spec;
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);
}
Your implementation must define the condition on which it should start the conversion. Also, you must define how to perform that conversion in both directions.
Once you create your implementation, you must create a
/META-INF/spring.factories file in which you provide the fully qualified name of your
implementation.
|
The following example shows a typical spring.factories
file:
org.springframework.cloud.contract.spec.ContractConverter=\
org.springframework.cloud.contract.verifier.converter.YamlContractConverter
3.2. Using the Custom Test Generator
If you want to generate tests for languages other than Java or you are not happy with the way the verifier builds Java tests, you can register your own implementation.
The SingleTestGenerator
interface lets you register your own implementation. The
following code listing shows the SingleTestGenerator
interface:
package org.springframework.cloud.contract.verifier.builder;
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;
}
}
}
Again, you must provide a spring.factories
file, such as the one shown in the following
example:
org.springframework.cloud.contract.verifier.builder.SingleTestGenerator=/
com.example.MyGenerator
3.3. Using the Custom Stub Generator
If you want to generate stubs for stub servers other than WireMock, you can plug in your
own implementation of the StubGenerator
interface. The following code listing shows the
StubGenerator
interface:
package org.springframework.cloud.contract.verifier.converter;
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";
}
}
Again, you must provide a spring.factories
file, such as the one shown in the following
example:
# Stub converters
org.springframework.cloud.contract.verifier.converter.StubGenerator=\
org.springframework.cloud.contract.verifier.wiremock.DslToWireMockClientConverter
The default implementation is the WireMock stub generation.
You can provide multiple stub generator implementations. For example, from a single DSL, you can produce both WireMock stubs and Pact files. |
3.4. Using the Custom Stub Runner
If you decide to use custom stub generation, you also need a custom way of running stubs with your different stub provider.
Assume that you use Moco to build your stubs and that you have written a stub generator and placed your stubs in a JAR file.
In order for Stub Runner to know how to run your stubs, you have to define a custom HTTP Stub server implementation, which might resemble the following example:
package org.springframework.cloud.contract.stubrunner.provider.moco
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")
}
}
Then you can register it in your spring.factories
file, as the following
example shows:
org.springframework.cloud.contract.stubrunner.HttpServerStub=\
org.springframework.cloud.contract.stubrunner.provider.moco.MocoHttpServerStub
Now you can run stubs with Moco.
If you do not provide any implementation, the default (WireMock) implementation is used. If you provide more than one, the first one on the list is used. |
3.5. Using the Custom Stub Downloader
You can customize the way your stubs are downloaded by creating an implementation of the
StubDownloaderBuilder
interface, as the following example shows:
package com.example;
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
}
}
}
}
Then you can register it in your spring.factories
file, as the following
example shows:
# Example of a custom Stub Downloader Provider
org.springframework.cloud.contract.stubrunner.StubDownloaderBuilder=\
com.example.CustomStubDownloaderBuilder
Now you can pick a folder with the source of your stubs.
If you do not provide any implementation, the default (scanning the classpath) is used.
If you provide the stubsMode = StubRunnerProperties.StubsMode.LOCAL or
stubsMode = StubRunnerProperties.StubsMode.REMOTE , the Aether implementation is used
If you provide more than one, the first one on the list is used.
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3.6. Using the SCM Stub Downloader
Whenever the repositoryRoot
starts with a SCM protocol
(currently, we support only git://
), the stub downloader tries
to clone the repository and use it as a source of contracts
to generate tests or stubs.
Through environment variables, system properties, or properties set inside the plugin or the contracts repository configuration, you can tweak the downloader’s behavior. The following table describes the available properties:
Type of a property |
Name of the property |
Description |
* * * |
master |
Which branch to checkout |
* * * |
Git clone username |
|
* * * |
Git clone password |
|
* * * |
10 |
Number of attempts to push the commits to |
* * * |
1000 |
Number of milliseconds to wait between attempts to push the commits to |