spring-cloud-contract/docs/modules/ROOT/pages/customization/pluggable-architecture.adoc

[[customization-pluggable-architecture]]
= Using the Pluggable Architecture

include::partial$_attributes.adoc[]

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).

[[customization-custom-contract-converter]]
== 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:

[source,java]
----
include::{contract_spec_path}/src/main/java/org/springframework/cloud/contract/spec/ContractConverter.java[indent=0,lines=17..-1]
----

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.

IMPORTANT: 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:

[source]
----
org.springframework.cloud.contract.spec.ContractConverter=\
org.springframework.cloud.contract.verifier.converter.YamlContractConverter
----

[[customization-custom-test-generator]]
== 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:

[source,groovy]
----
include::{verifier_root_path}/src/main/java/org/springframework/cloud/contract/verifier/builder/SingleTestGenerator.java[indent=0,lines=17..-1]
----

Again, you must provide a `spring.factories` file, such as the one shown in the following
example:

[source]
----
org.springframework.cloud.contract.verifier.builder.SingleTestGenerator=/
com.example.MyGenerator
----

[[customization-custom-stub-generator]]
== 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:

[source,groovy]
----
include::{converters_path}/src/main/java/org/springframework/cloud/contract/verifier/converter/StubGenerator.java[indent=0,lines=16..-1]
----

Again, you must provide a `spring.factories` file, such as the one shown in the following
example:

[source]
----
include::{converters_path}/src/main/resources/META-INF/spring.factories[indent=0]
----

The default implementation is the WireMock stub generation.

TIP: You can provide multiple stub generator implementations. For example, from a single
DSL, you can produce both WireMock stubs and Pact files.

[[customization-custom-stub-runner]]
== 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 https://github.com/dreamhead/moco[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:

[source,groovy]
----
include::{tests_path}/spring-cloud-contract-stub-runner-moco/src/test/groovy/org/springframework/cloud/contract/stubrunner/provider/moco/MocoHttpServerStub.groovy[indent=0,lines=16..-1]
----

Then you can register it in your `spring.factories` file, as the following
example shows:

[source]
----
org.springframework.cloud.contract.stubrunner.HttpServerStub=\
org.springframework.cloud.contract.stubrunner.provider.moco.MocoHttpServerStub
----

Now you can run stubs with Moco.

IMPORTANT: 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.

[[customization-custom-stub-downloader]]
== 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:

[source,java]
----
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:

[source]
----
# 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.

IMPORTANT: 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.

[[scm-stub-downloader]]
== 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:

.SCM Stub Downloader properties
|===
|Type of a property |Name of the property | Description
|
* `git.branch` (plugin prop)

* `stubrunner.properties.git.branch` (system prop)

* `STUBRUNNER_PROPERTIES_GIT_BRANCH` (env prop)
|master
|Which branch to checkout

|
* `git.username` (plugin prop)

* `stubrunner.properties.git.username` (system prop)

* `STUBRUNNER_PROPERTIES_GIT_USERNAME` (env prop)
|
|Git clone username

|
* `git.password` (plugin prop)

* `stubrunner.properties.git.password` (system prop)

* `STUBRUNNER_PROPERTIES_GIT_PASSWORD` (env prop)
|
|Git clone password

|
* `git.no-of-attempts` (plugin prop)

* `stubrunner.properties.git.no-of-attempts` (system prop)

* `STUBRUNNER_PROPERTIES_GIT_NO_OF_ATTEMPTS` (env prop)
|10
|Number of attempts to push the commits to `origin`

|
* `git.wait-between-attempts` (Plugin prop)

* `stubrunner.properties.git.wait-between-attempts`  (system prop)

* `STUBRUNNER_PROPERTIES_GIT_WAIT_BETWEEN_ATTEMPTS`  (env prop)
|1000
|Number of milliseconds to wait between attempts to push the commits to `origin`
|===