[[howto]]
= "`How-to`" Guides
include::_attributes.adoc[]

This section provides answers to some common "`how do I do that...?`" questions
that often arise when using {project-full-name}. Its coverage is not exhaustive, but it
does cover quite a lot.

If you have a specific problem that we do not cover here, you might want to check out
https://stackoverflow.com/tags/{project-name}[stackoverflow.com] to see if someone has
already provided an answer. Stack Overflow is also a great place to ask new questions (please use
the `{project-name}` tag).

We are also more than happy to extend this section. If you want to add a "`how-to`",
send us a {github-code}[pull request].

[[why-spring-cloud-contract]]
== Why use Spring Cloud Contract?

Spring Cloud Contract works great in a polyglot environment. This project has a lot of
really interesting features. Quite a few of these features definitely make
Spring Cloud Contract Verifier stand out on the market of Consumer Driven Contract
(CDC) tooling. The most interesting features include the following:

- Ability to do CDC with messaging.
- Clear and easy to use, statically typed DSL.
- Ability to copy-paste your current JSON file to the contract and edit only its elements.
- Automatic generation of tests from the defined contract.
- Stub Runner functionality: The stubs are automatically downloaded at runtime from Nexus or Artifactory.
- Spring Cloud integration: No discovery service is needed for integration tests.
- Ability to add support for any language & framework through Docker.

[[how-to-not-write-contracts-in-groovy]]
== How Can I Write Contracts in a Language Other than Groovy?

You can write a contract in YAML. See <<project-features.adoc#contract-dsl, this section>> for more information.

We are working on allowing more ways of describing the contracts. You can check the {github-issues}[github-issues] for more information.

[[how-to-provide-dynamic-values]]
== How Can I Provide Dynamic Values to a Contract?

One of the biggest challenges related to stubs is their reusability. Only if they can be widely used can they serve their purpose.
The hard-coded values (such as dates and IDs) of request and response elements generally make that difficult.
Consider the following JSON request:

====
[source,json,indent=0]
----
{
    "time" : "2016-10-10 20:10:15",
    "id" : "9febab1c-6f36-4a0b-88d6-3b6a6d81cd4a",
    "body" : "foo"
}
----
====

Now consider the following JSON response:

====
[source,json,indent=0]
----
{
    "time" : "2016-10-10 21:10:15",
    "id" : "c4231e1f-3ca9-48d3-b7e7-567d55f0d051",
    "body" : "bar"
}
----
====

Imagine the pain required to set the proper value of the `time` field (assume that this content is generated by the
database) by changing the clock in the system or by providing stub implementations of data providers. The same is related
to the `id` field. You could create a stubbed implementation of UUID generator, but doing so makes little sense.

So, as a consumer, you want to send a request that matches any form of a time or any UUID. That way, your system
works as usual, generating data without you having to stub out anything. Assume that, in case of the aforementioned
JSON, the most important part is the `body` field. You can focus on that and provide matching for other fields. In other words,
you would like the stub to work as follows:

====
[source,json,indent=0]
----
{
    "time" : "SOMETHING THAT MATCHES TIME",
    "id" : "SOMETHING THAT MATCHES UUID",
    "body" : "foo"
}
----
====

As far as the response goes, as a consumer, you need a concrete value on which you can operate.
Consequently, the following JSON is valid:

====
[source,json,indent=0]
----
{
    "time" : "2016-10-10 21:10:15",
    "id" : "c4231e1f-3ca9-48d3-b7e7-567d55f0d051",
    "body" : "bar"
}
----
====

In the previous sections, we generated tests from contracts. So, from the producer's side, the situation looks
much different. We parse the provided contract, and, in the test, we want to send a real request to your endpoints.
So, for the case of a producer for the request, we cannot have any sort of matching. We need concrete values on which the
producer's backend can work. Consequently, the following JSON would be valid:

====
[source,json,indent=0]
----
{
    "time" : "2016-10-10 20:10:15",
    "id" : "9febab1c-6f36-4a0b-88d6-3b6a6d81cd4a",
    "body" : "foo"
}
----
====

On the other hand, from the point of view of the validity of the contract, the response does not necessarily have to
contain concrete values for `time` or `id`. Suppose you generate those on the producer side. Again, you
have to do a lot of stubbing to ensure that you always return the same values. That is why, from the producer's side,
you might want the following response:

====
[source,json,indent=0]
----
{
    "time" : "SOMETHING THAT MATCHES TIME",
    "id" : "SOMETHING THAT MATCHES UUID",
    "body" : "bar"
}
----
====

How can you then provide a matcher for the consumer and a concrete value for the producer (and the opposite at some other time)?
Spring Cloud Contract lets you provide a dynamic value. That means that it can differ for both
sides of the communication.

You can read more about this in the <<project-features.adoc#contract-dsl, Contract DSL>> section.

IMPORTANT: Read the https://groovy-lang.org/json.html[Groovy docs related to JSON] to understand how to
properly structure the request and response bodies.

[[how-to-do-stubs-versioning]]
== How to Do Stubs versioning?

This section covers versioning of the stubs, which you can handle in a number of different ways:

* <<how-to-api-versioning>>
* <<how-to-jar-versioning>>
* <<how-to-dev-or-prod-stubs>>

[[how-to-api-versioning]]
=== API Versioning

What does versioning really mean? If you refer to the API version, there are
different approaches:

- Use hypermedia links and do not version your API by any means
- Pass the version through headers and URLs

We do not try to answer the question of which approach is better. You should pick whatever
suits your needs and lets you generate business value.

Assume that you do version your API. In that case, you should provide as many contracts with as many versions as you support.
You can create a subfolder for every version or append it to the contract name -- whatever suits you best.

[[how-to-jar-versioning]]
=== JAR versioning

If, by versioning, you mean the version of the JAR that contains the stubs, then there are essentially two main approaches.

Assume that you do continuous delivery and deployment, which means that you generate a new version of
the jar each time you go through the pipeline and that the jar can go to production at any time. For example, your jar version
looks like the following (because it got built on the 20.10.2016 at 20:15:21) :

====
[source,groovy,indent=0]
----
1.0.0.20161020-201521-RELEASE
----
====

In that case, your generated stub jar should look like the following:

====
[source,groovy,indent=0]
----
1.0.0.20161020-201521-RELEASE-stubs.jar
----
====

In this case, you should, inside your `application.yml` or `@AutoConfigureStubRunner` when
referencing stubs, provide the latest version of the stubs. You can do that by passing the
`+` sign. the following example shows how to do so:

====
[source,java,indent=0]
----
@AutoConfigureStubRunner(ids = {"com.example:http-server-dsl:+:stubs:8080"})
----
====

If the versioning, however, is fixed (for example, `1.0.4.RELEASE` or `2.1.1`), you have to set the concrete value of the jar
version. The following example shows how to do so for version 2.1.1:

====
[source,java,indent=0]
----
@AutoConfigureStubRunner(ids = {"com.example:http-server-dsl:2.1.1:stubs:8080"})
----
====

[[how-to-dev-or-prod-stubs]]
=== Development or Production Stubs

You can manipulate the classifier to run the tests against the current development version
of the stubs of other services or the ones that were deployed to production. If you alter
your build to deploy the stubs with the `prod-stubs` classifier once you reach production
deployment, you can run tests in one case with development stubs and in another case with production stubs.

The following example works for tests that use the development version of the stubs:

====
[source,java,indent=0]
----
@AutoConfigureStubRunner(ids = {"com.example:http-server-dsl:+:stubs:8080"})
----
====

The following example works for tests that use the production version of stubs:

====
[source,java,indent=0]
----
@AutoConfigureStubRunner(ids = {"com.example:http-server-dsl:+:prod-stubs:8080"})
----
====

You can also pass those values also in properties from your deployment pipeline.

[[how-to-common-repo-with-contracts]]
== How Can I use a Common Repository with Contracts Instead of Storing Them with the Producer?

Another way of storing contracts, rather than having them with the producer, is to keep
them in a common place. This situation can be related to security issues (where the
consumers cannot clone the producer's code). Also, if you keep contracts in a single place,
then you, as a producer, know how many consumers you have and which consumer you may break
with your local changes.

[[how-to-repo-structure]]
=== Repo Structure

Assume that we have a producer with coordinates of `com.example:server` and three
consumers: `client1`, `client2`, and `client3`. Then, in the repository with common
contracts, you could have the following setup (which you can check out
https://github.com/spring-cloud/spring-cloud-contract/tree/{github-tag}/samples/standalone/contracts[here]).
The following listing shows such a structure:

====
[source,bash,indent=0]
----
├── com
│   └── example
│       └── server
│           ├── client1
│           │   └── expectation.groovy
│           ├── client2
│           │   └── expectation.groovy
│           ├── client3
│           │   └── expectation.groovy
│           └── pom.xml
├── mvnw
├── mvnw.cmd
├── pom.xml
└── src
    └── assembly
        └── contracts.xml
----
====

Under the slash-delimited `groupid/artifact id` folder (`com/example/server`), you have
expectations of the three consumers (`client1`, `client2`, and `client3`). Expectations are the standard Groovy DSL
contract files, as described throughout this documentation. This repository has to produce a JAR file that maps
one-to-one to the contents of the repository.

The following example shows a `pom.xml` file inside the `server` folder:

====
[source,xml,indent=0]
----
include::{introduction_url}/samples/standalone/contracts/com/example/server/pom.xml[indent=0]
----
====

There are no dependencies other than the Spring Cloud Contract Maven Plugin.
Those `pom.xml` files are necessary for the consumer side to run `mvn clean install -DskipTests` to locally install
the stubs of the producer project.

The `pom.xml` file in the root folder can look like the following:

====
[source,xml,indent=0]
----
include::{introduction_url}/samples/standalone/contracts/pom.xml[indent=0]
----
====

It uses the assembly plugin to build the JAR with all the contracts. The following example
shows such a setup:

====
[source,xml,indent=0]
----
include::{introduction_url}/samples/standalone/contracts/src/assembly/contracts.xml[indent=0]
----
====

[[how-to-workflow]]
=== Workflow

The workflow assumes that Spring Cloud Contract is set up both on the consumer and on the
producer side. There is also the proper plugin setup in the common repository with
contracts. The CI jobs are set for a common repository to build an artifact of all
contracts and upload it to Nexus or Artifactory. The following image shows the UML for this
workflow:

[plantuml, how-to-common-repo, png]
----
"API Consumer"->"Common repo": create a folder \nfor producer [API Producer]
"API Consumer"->"Common repo": under [API Producer] create a folder \nfor consumer \n[API Consumer]
"API Consumer"->"Common repo": define contracts under \n[API Consumer] folder
"API Consumer"->"Common repo": install stubs of [API Producer]\nin local storage
"Common repo"->"Common Repo\nSCC Plugin": install stubs \nin local storage. \nDon't generate tests.
"Common Repo\nSCC Plugin"->"Local storage": install stubs
"Local storage"->"Common Repo\nSCC Plugin": stubs installed
"API Consumer"->"API Consumer": write a SCC Stub Runner \nbased contract test
"API Consumer"->"API Consumer\nSCC Stub Runner": fetch the stubs\n of [API Producer] \nfrom local storage
"API Consumer\nSCC Stub Runner"->"Local storage": test asks for [API Producer] stubs
"Local storage"->"API Consumer\nSCC Stub Runner": [API Producer] stubs found
"API Consumer\nSCC Stub Runner"->"API Consumer\nSCC Stub Runner": run in memory\n HTTP server stubs
"API Consumer\nSCC Stub Runner"->"API Consumer": HTTP server stubs running,\n ready for tests
"API Consumer"->"API Consumer\nSCC Stub Runner": send a request \nto the HTTP server stub
"API Consumer\nSCC Stub Runner"->"API Consumer": communication is correct. \nTests are passing
"API Consumer"->"Common repo": file pull request \nwith contracts
"API Producer"->"Common repo": take over \nthe pull request
"API Producer"->"Common repo": install the JAR \nwith all contracts\n in local storage
"Common repo"->"Local storage": install the JAR
"Local storage"->"Common repo": contracts JAR installed
"API Producer"->"Producer Build": run the build \nand fetch contracts from \nlocal storage
"Producer Build"->"Producer\nSCC Plugin": generate \ntests, stubs and stubs \nartifact (e.g. stubs-jar)
"Producer\nSCC Plugin"->"Local storage": fetch contract definitions for [API Prodcer]
"Local storage"->"Producer\nSCC Plugin": contracts fetched
"Producer\nSCC Plugin"->"Producer Build": tests and stubs created
"Producer Build"->"Nexus / Artifactory": upload contracts \nand stubs and the project arifact
"Producer Build"->"API Producer": Build successful
"API Producer"->"Common repo": merge the pull request
"Common repo"->"Nexus / Artifactory": upload the fresh JAR \nwith contract definitions
"API Producer"->"API Producer": start fetching contract definitions \nfrom Nexus / Artifactory
----

[[how-to-workflow-consumer]]
=== Consumer

When the consumer wants to work on the contracts offline, instead of cloning the producer
code, the consumer team clones the common repository, goes to the required producer's
folder (for example, `com/example/server`) and runs `mvn clean install -DskipTests` to
locally install the stubs converted from the contracts.

TIP: You need to have https://maven.apache.org/download.cgi[Maven installed locally].

[[how-to-workflow-producer]]
=== Producer

As a producer, you can alter the Spring Cloud Contract Verifier to provide the URL and
the dependency of the JAR that contains the contracts, as follows:

====
[source,xml,indent=0]
----
include::{introduction_url}/spring-cloud-contract-tools/spring-cloud-contract-maven-plugin/src/test/projects/basic-remote-contracts/pom-with-repo.xml[tags=remote_config,indent=0]
----
====

With this setup, the JAR with a `groupid` of `com.example.standalone` and an `artifactid` of
`contracts` is downloaded from `https://link/to/your/nexus/or/artifactory/or/sth`. It is
then unpacked in a local temporary folder, and the contracts present in
`com/example/server` are picked as the ones used to generate the tests and the stubs. Due
to this convention, the producer team can know which consumer teams are broken when
some incompatible changes are made.

The rest of the flow looks the same.

[[how-to-define-messaging-contracts-per-topic]]
=== How Can I Define Messaging Contracts per Topic Rather than per Producer?

To avoid messaging contracts duplication in the common repository, when a few producers write messages to one topic,
we could create a structure in which the REST contracts are placed in a folder per producer and messaging
contracts are placed in the folder per topic.

[[how-to-define-messaging-contracts-per-topic-maven]]
==== For Maven Projects

To make it possible to work on the producer side, we should specify an inclusion pattern for
filtering common repository jar files by messaging topics we are interested in. The
`includedFiles` property of the Maven Spring Cloud Contract plugin
lets us do so. Also, `contractsPath` need to be specified, since the default path would be
the common repository `groupid/artifactid`. The following example shows a Maven
plugin for Spring Cloud Contract:

====
[source,xml,indent=0]
----
<plugin>
   <groupId>org.springframework.cloud</groupId>
   <artifactId>spring-cloud-contract-maven-plugin</artifactId>
   <version>${spring-cloud-contract.version}</version>
   <configuration>
      <contractsMode>REMOTE</contractsMode>
      <contractsRepositoryUrl>https://link/to/your/nexus/or/artifactory/or/sth</contractsRepositoryUrl>
      <contractDependency>
         <groupId>com.example</groupId>
         <artifactId>common-repo-with-contracts</artifactId>
         <version>+</version>
      </contractDependency>
      <contractsPath>/</contractsPath>
      <baseClassMappings>
         <baseClassMapping>
            <contractPackageRegex>.*messaging.*</contractPackageRegex>
            <baseClassFQN>com.example.services.MessagingBase</baseClassFQN>
         </baseClassMapping>
         <baseClassMapping>
            <contractPackageRegex>.*rest.*</contractPackageRegex>
            <baseClassFQN>com.example.services.TestBase</baseClassFQN>
         </baseClassMapping>
      </baseClassMappings>
      <includedFiles>
         <includedFile>**/${project.artifactId}/**</includedFile>
         <includedFile>**/${first-topic}/**</includedFile>
         <includedFile>**/${second-topic}/**</includedFile>
      </includedFiles>
   </configuration>
</plugin>
----
====

NOTE: Many of the values in the preceding Maven plugin can be changed. We included it for
illustration purposes rather than trying to provide a "`typical`" example.

[[how-to-define-messaging-contracts-per-topic-gradle]]
==== For Gradle Projects

To work with a Gradle project:

. Add a custom configuration for the common repository dependency, as follows:
+
====
[source,groovy,indent=0]
----
ext {
    contractsGroupId = "com.example"
    contractsArtifactId = "common-repo"
    contractsVersion = "1.2.3"
}

configurations {
    contracts {
        transitive = false
    }
}
----
====

. Add the common repository dependency to your classpath, as follows:
+
====
[source,groovy,indent=0]
----
dependencies {
    contracts "${contractsGroupId}:${contractsArtifactId}:${contractsVersion}"
    testCompile "${contractsGroupId}:${contractsArtifactId}:${contractsVersion}"
}
----
====

. Download the dependency to an appropriate folder, as follows:
+
====
[source,groovy,indent=0]
----
task getContracts(type: Copy) {
    from configurations.contracts
    into new File(project.buildDir, "downloadedContracts")
}
----
====

. Unzip the JAR, as follows:
+
====
[source,groovy,indent=0]
----
task unzipContracts(type: Copy) {
    def zipFile = new File(project.buildDir, "downloadedContracts/${contractsArtifactId}-${contractsVersion}.jar")
    def outputDir = file("${buildDir}/unpackedContracts")

    from zipTree(zipFile)
    into outputDir
}
----
====

. Cleanup unused contracts, as follows:
+
====
[source,groovy,indent=0]
----
task deleteUnwantedContracts(type: Delete) {
    delete fileTree(dir: "${buildDir}/unpackedContracts",
        include: "**/*",
        excludes: [
            "**/${project.name}/**"",
            "**/${first-topic}/**",
            "**/${second-topic}/**"])
}
----
====

. Create task dependencies, as follows:
+
====
[source,groovy,indent=0]
----
unzipContracts.dependsOn("getContracts")
deleteUnwantedContracts.dependsOn("unzipContracts")
build.dependsOn("deleteUnwantedContracts")
----
====

. Configure the plugin by specifying the directory that contains the contracts, by setting
the `contractsDslDir` property, as follows:
+
====
[source,groovy,indent=0]
----
contracts {
    contractsDslDir = new File("${buildDir}/unpackedContracts")
}
----
====

[[how-to-use-git-as-storage]]
== How Can I Use Git as the Storage for Contracts and Stubs?

In the polyglot world, there are languages that do not use binary storage, as
Artifactory and Nexus do. Starting from Spring Cloud Contract version 2.0.0, we provide
mechanisms to store contracts and stubs in a SCM (Source Control Management) repository. Currently, the
only supported SCM is Git.

The repository would have to have the following setup
(which you can checkout from https://github.com/spring-cloud-samples/spring-cloud-contract-samples/tree/{samples_branch}/contracts_git/[here]):

====
[source,indent=0]
----
.
└── META-INF
    └── com.example
        └── beer-api-producer-git
            └── 0.0.1-SNAPSHOT
                ├── contracts
                │   └── beer-api-consumer
                │       ├── messaging
                │       │   ├── shouldSendAcceptedVerification.groovy
                │       │   └── shouldSendRejectedVerification.groovy
                │       └── rest
                │           ├── shouldGrantABeerIfOldEnough.groovy
                │           └── shouldRejectABeerIfTooYoung.groovy
                └── mappings
                    └── beer-api-consumer
                        └── rest
                            ├── shouldGrantABeerIfOldEnough.json
                            └── shouldRejectABeerIfTooYoung.json
----
====

Under the `META-INF` folder:

* We group applications by `groupId` (such as `com.example`).
* Each application is represented by its `artifactId` (for example, `beer-api-producer-git`).
* Next, each application is organized by its version (such as `0.0.1-SNAPSHOT`). Starting
from Spring Cloud Contract version `2.1.0`, you can specify the versions as follows
(assuming that your versions follow semantic versioning):
** `+` or `latest`: To find the latest version of your stubs (assuming that the snapshots
are always the latest artifact for a given revision number). That means:
*** If you have `1.0.0.RELEASE`, `2.0.0.BUILD-SNAPSHOT`, and `2.0.0.RELEASE`, we assume
that the latest is `2.0.0.BUILD-SNAPSHOT`.
*** If you have `1.0.0.RELEASE` and `2.0.0.RELEASE`, we assume that the latest is `2.0.0.RELEASE`.
*** If you have a version called `latest` or `+`, we will pick that folder.
** `release`: To find the latest release version of your stubs. That means:
*** If you have `1.0.0.RELEASE`, `2.0.0.BUILD-SNAPSHOT`, and `2.0.0.RELEASE` we assume
that the latest is `2.0.0.RELEASE`.
*** If you have a version called `release`, we pick that folder.

Finally, there are two folders:

* `contracts`: The good practice is to store the contracts required by each
consumer in the folder with the consumer name (such as `beer-api-consumer`). That way, you
can use the `stubs-per-consumer` feature. Further directory structure is arbitrary.
* `mappings`: The Maven or Gradle Spring Cloud Contract plugins push
the stub server mappings in this folder. On the consumer side, Stub Runner scans this folder
to start stub servers with stub definitions. The folder structure is a copy
of the one created in the `contracts` subfolder.

[[how-to-protocol-convention]]
=== Protocol Convention

To control the type and location of the source of contracts (whether
binary storage or an SCM repository), you can use the protocol in the URL of
the repository. Spring Cloud Contract iterates over registered protocol resolvers
and tries to fetch the contracts (by using a plugin) or stubs (from Stub Runner).

For the SCM functionality, currently, we support the Git repository. To use it,
in the property where the repository URL needs to be placed, you have to prefix
the connection URL with `git://`. The following listing shows some examples:

====
[source,indent=0]
----
git://file:///foo/bar
git://https://github.com/spring-cloud-samples/spring-cloud-contract-nodejs-contracts-git.git
git://git@github.com:spring-cloud-samples/spring-cloud-contract-nodejs-contracts-git.git
----
====

[[how-to-protocol-convention-producer]]
=== Producer

For the producer, to use the SCM (Source Control Management) approach, we can reuse the
same mechanism we use for external contracts. We route Spring Cloud Contract
to use the SCM implementation from the URL that starts with
the `git://` protocol.

IMPORTANT: You have to manually add the `pushStubsToScm`
goal in Maven or use (bind) the `pushStubsToScm` task in
Gradle. We do not push stubs to the `origin` of your git
repository.

The following listing includes the relevant parts both Maven and Gradle build files:

====
[source,xml,indent=0,role="primary"]
.Maven
----
<plugin>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-contract-maven-plugin</artifactId>
    <version>${spring-cloud-contract.version}</version>
    <extensions>true</extensions>
    <configuration>
        <!-- Base class mappings etc. -->

        <!-- We want to pick contracts from a Git repository -->
        <contractsRepositoryUrl>git://https://github.com/spring-cloud-samples/spring-cloud-contract-nodejs-contracts-git.git</contractsRepositoryUrl>

        <!-- We reuse the contract dependency section to set up the path
        to the folder that contains the contract definitions. In our case the
        path will be /groupId/artifactId/version/contracts -->
        <contractDependency>
            <groupId>${project.groupId}</groupId>
            <artifactId>${project.artifactId}</artifactId>
            <version>${project.version}</version>
        </contractDependency>

        <!-- The contracts mode can't be classpath -->
        <contractsMode>REMOTE</contractsMode>
    </configuration>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <!-- By default we will not push the stubs back to SCM,
                you have to explicitly add it as a goal -->
                <goal>pushStubsToScm</goal>
            </goals>
        </execution>
    </executions>
</plugin>
----

[source,groovy,indent=0,role="secondary"]
.Gradle
----
contracts {
	// We want to pick contracts from a Git repository
	contractDependency {
		stringNotation = "${project.group}:${project.name}:${project.version}"
	}
	/*
	We reuse the contract dependency section to set up the path
	to the folder that contains the contract definitions. In our case the
	path will be /groupId/artifactId/version/contracts
	 */
	contractRepository {
		repositoryUrl = "git://https://github.com/spring-cloud-samples/spring-cloud-contract-nodejs-contracts-git.git"
	}
	// The mode can't be classpath
	contractsMode = "REMOTE"
	// Base class mappings etc.
}

/*
In this scenario we want to publish stubs to SCM whenever
the `publish` task is invoked
*/
publish.dependsOn("publishStubsToScm")
----
====

You can also further customize the `publishStubsToScm` gradle task. In the following example,
the task is customized to pick contracts from a local git repository:

====
[source,groovy,indent=0]
.gradle
----
publishStubsToScm {
	// We want to modify the default set up of the plugin when publish stubs to scm is called
	// We want to pick contracts from a Git repository
	contractDependency {
		stringNotation = "${project.group}:${project.name}:${project.version}"
	}
	/*
	We reuse the contract dependency section to set up the path
	to the folder that contains the contract definitions. In our case the
	path will be /groupId/artifactId/version/contracts
	 */
	contractRepository {
		repositoryUrl = "git://file://${new File(project.rootDir, "../target")}/contract_empty_git/"
	}
	// We set the contracts mode to `LOCAL`
	contractsMode = "LOCAL"
	}
----
====

IMPORTANT:: Starting with the `2.3.0.RELEASE`, the `customize{}` closure previously used for the
`publishStubsToScm` customization is no longer available. The settings should be applied directly
within the `publishStubsToScm` closure, as in the preceding example.

With such a setup:

* A git project is cloned to a temporary directory
* The SCM stub downloader goes to the `META-INF/groupId/artifactId/version/contracts` folder
to find contracts. For example, for `com.example:foo:1.0.0`, the path would be
`META-INF/com.example/foo/1.0.0/contracts`.
* Tests are generated from the contracts.
* Stubs are created from the contracts.
* Once the tests pass, the stubs are committed in the cloned repository.
* Finally, a push is sent to that repo's `origin`.

[[how-to-protocol-convention-producer-with-contracts-stored-locally]]
=== Producer with Contracts Stored Locally

Another option to use the SCM as the destination for stubs and contracts is to store the
contracts locally, with the producer, and only push the contracts and the stubs to SCM.
The following listing shows the setup required to achieve this with Maven and Gradle:

====
[source,xml,indent=0,role="primary"]
.Maven
----
include::{samples_url}/producer_with_empty_git/pom.xml[tags=plugin,indent=0]
----

[source,groovy,indent=0,role="secondary"]
.Gradle
----
include::{samples_url}/producer_with_empty_git/build.gradle[tags=plugin,indent=0]
----
====

With such a setup:

* Contracts from the default `src/test/resources/contracts` directory are picked.
* Tests are generated from the contracts.
* Stubs are created from the contracts.
* Once the tests pass:
** The git project is cloned to a temporary directory.
** The stubs and contracts are committed in the cloned repository.
* Finally, a push is done to that repository's `origin`.

[[how-to-protocol-convention-contracts-producer-stubs-external]]
=== Keeping Contracts with the Producer and Stubs in an External Repository

You can also keep the contracts in the producer repository but keep the stubs in an external git repository.
This is most useful when you want to use the base consumer-producer collaboration flow but cannot
use an artifact repository to store the stubs.

To do so, use the usual producer setup and then add the `pushStubsToScm` goal and set
`contractsRepositoryUrl` to the repository where you want to keep the stubs.

[[how-to-protocol-convention-contracts-producer-stubs-external-consumer]]
=== Consumer

On the consumer side, when passing the `repositoryRoot` parameter,
either from the `@AutoConfigureStubRunner` annotation, the
JUnit 4 rule, JUnit 5 extension, or properties, you can pass the URL of the
SCM repository, prefixed with the `git://` protocol. The following example shows how to do so:

====
[source,java,indent=0]
----
@AutoConfigureStubRunner(
    stubsMode="REMOTE",
    repositoryRoot="git://https://github.com/spring-cloud-samples/spring-cloud-contract-nodejs-contracts-git.git",
    ids="com.example:bookstore:0.0.1.RELEASE"
)
----
====

With such a setup:

* The git project is cloned to a temporary directory.
* The SCM stub downloader goes to the `META-INF/groupId/artifactId/version/` folder
to find stub definitions and contracts. For example, for `com.example:foo:1.0.0`, the path would be
`META-INF/com.example/foo/1.0.0/`.
* Stub servers are started and fed with mappings.
* Messaging definitions are read and used in the messaging tests.

[[how-to-debug]]
== How Can I Debug the Request/Response Being Sent by the Generated Tests Client?

The generated tests all boil down to RestAssured in some form or fashion. RestAssured
relies on the https://hc.apache.org/httpcomponents-client-ga/[Apache HttpClient].
HttpClient has a facility called
https://hc.apache.org/httpcomponents-client-ga/logging.html#Wire_Logging[wire logging],
which logs the entire request and response to HttpClient. Spring Boot has a logging
https://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html[common application property]
for doing this sort of thing. To use it, add it to your application properties, as follows:

====
[source,properties,indent=0]
----
logging.level.org.apache.http.wire=DEBUG
----
====

[[how-to-debug-wiremock]]
== How Can I Debug the Mapping, Request, or Response Being Sent by WireMock?

Starting from version `1.2.0`, we set WireMock logging to
`info` and set the WireMock notifier to being verbose. Now you can
exactly know what request was received by the WireMock server and which
matching response definition was picked.

To turn off this feature, set WireMock logging to `ERROR`, as follows:

====
[source,properties,indent=0]
----
logging.level.com.github.tomakehurst.wiremock=ERROR
----
====

[[how-to-see-registered-stubs]]
== How Can I See What Got Registered in the HTTP Server Stub?

You can use the `mappingsOutputFolder` property on `@AutoConfigureStubRunner`, `StubRunnerRule`, or
`StubRunnerExtension` to dump all mappings for each artifact ID. Also, the port at which the given stub server
was started is attached.

[[how-to-reference-text-from-file]]
== How Can I Reference Text from File?

In version 1.2.0, we added this ability. You can call a `file(...)` method in the
DSL and provide a path relative to where the contract lies.
If you use YAML, you can use the `bodyFromFile` property.

[[how-to-generate-pact-from-scc]]
== How Can I Generate Pact, YAML, or X files from Spring Cloud Contract Contracts?

Spring Cloud Contract comes with a `ToFileContractsTransformer` class that lets you dump
contracts as files for the given `ContractConverter`. It contains a `static void main`
method that lets you run the transformer as an executable. It takes the following
arguments:

- argument 1 : `FQN`: Fully qualified name of the `ContractConverter` (for example, `PactContractConverter`). *REQUIRED*.
- argument 2 : `path`: Path where the dumped files should be stored. *OPTIONAL* -- defaults to `target/converted-contracts`.
- argument 3 : `path`: Path were the contracts should be searched for. *OPTIONAL* -- defaults to `src/test/resources/contracts`.

After calling the transformer, the Spring Cloud Contract files are processed and,
depending on the provided FQN of the `ContractTransformer`, the contracts are transformed
to the required format and dumped to the provided folder.

The following example shows how to configure Pact integration for both Maven and Gradle:

====
[source,xml,indent=0,role="primary"]
.Maven
----
<plugin>
	<groupId>org.codehaus.mojo</groupId>
	<artifactId>exec-maven-plugin</artifactId>
	<version>1.6.0</version>
	<executions>
		<execution>
			<id>convert-dsl-to-pact</id>
			<phase>process-test-classes</phase>
			<configuration>
				<classpathScope>test</classpathScope>
				<mainClass>
					org.springframework.cloud.contract.verifier.util.ToFileContractsTransformer
				</mainClass>
				<arguments>
					<argument>
						org.springframework.cloud.contract.verifier.spec.pact.PactContractConverter
					</argument>
					<argument>${project.basedir}/target/pacts</argument>
					<argument>
						${project.basedir}/src/test/resources/contracts
					</argument>
				</arguments>
			</configuration>
			<goals>
				<goal>java</goal>
			</goals>
		</execution>
	</executions>
</plugin>
----

[source,groovy,indent=0,role="secondary"]
.Gradle
----
task convertContracts(type: JavaExec) {
    main = "org.springframework.cloud.contract.verifier.util.ToFileContractsTransformer"
    classpath = sourceSets.test.compileClasspath
    args("org.springframework.cloud.contract.verifier.spec.pact.PactContractConverter",
            "${project.rootDir}/build/pacts", "${project.rootDir}/src/test/resources/contracts")
}

test.dependsOn("convertContracts")
----
====

[[how-to-work-with-transitivie]]
== How Can I Work with Transitive Dependencies?

The Spring Cloud Contract plugins add the tasks that create the stubs jar for you. One
problem that arises is that, when reusing the stubs, you can mistakenly import all of
that stub's dependencies. When building a Maven artifact, even though you have a couple
of different jars, all of them share one `pom.xml` file, as the following listing shows:

====
[source,bash,indent=0]
----
├── producer-0.0.1.BUILD-20160903.075506-1-stubs.jar
├── producer-0.0.1.BUILD-20160903.075506-1-stubs.jar.sha1
├── producer-0.0.1.BUILD-20160903.075655-2-stubs.jar
├── producer-0.0.1.BUILD-20160903.075655-2-stubs.jar.sha1
├── producer-0.0.1.BUILD-SNAPSHOT.jar
├── producer-0.0.1.BUILD-SNAPSHOT.pom
├── producer-0.0.1.BUILD-SNAPSHOT-stubs.jar
├── ...
└── ...
----
====

There are three possibilities of working with those dependencies so as not to have any
issues with transitive dependencies:

* Mark all application dependencies as optional
* Create a separate `artifactid` for the stubs
* Exclude dependencies on the consumer side

[[how-to-work-with-transitivie-optional]]
=== How Can I Mark All Application Dependencies as Optional?

If, in the `producer` application, you mark all of your dependencies as optional,
when you include the `producer` stubs in another application (or when that
dependency gets downloaded by Stub Runner), then, since all of the dependencies are
optional, they do not get downloaded.

[[how-to-work-with-transitivie-separate]]
=== How can I Create a Separate `artifactid` for the Stubs?

If you create a separate `artifactid`, you can set it up in whatever way you wish.
For example, you might decide to have no dependencies at all.

[[how-to-work-with-transitivie-exclude]]
=== How can I Exclude Dependencies on the Consumer Side?

As a consumer, if you add the stub dependency to your classpath, you can explicitly exclude the unwanted dependencies.

[[contract-dsl-rest-docs]]
== How Can I Generate Spring REST Docs Snippets from the Contracts?

When you want to include the requests and responses of your API by using Spring REST Docs,
you only need to make some minor changes to your setup if you are using MockMvc and RestAssuredMockMvc.
To do so, include the following dependencies (if you have not already done so):

====
[source,xml,indent=0,subs="verbatim,attributes",role="primary"]
.maven
----
include::{standalone_restdocs_path}/http-server/pom.xml[tags=dependencies,indent=0]
----

[source,groovy,indent=0,subs="verbatim,attributes",role="secondary"]
.gradle
----
include::{standalone_restdocs_path}/http-server/build.gradle[tags=dependencies,indent=0]
----
====

Next, you need to make some changes to your base class. The following examples use
`WebAppContext` and the standalone option with RestAssured:

====
[source,java,indent=0,subs="verbatim,attributes",role="primary"]
.WebAppContext
----
include::{standalone_restdocs_path}/http-server/src/test/java/com/example/fraud/FraudBaseWithWebAppSetup.java[tags=base_class,indent=0]
----

[source,java,indent=0,subs="verbatim,attributes",role="secondary"]
.Standalone
----
include::{standalone_restdocs_path}/http-server/src/test/java/com/example/fraud/FraudBaseWithStandaloneSetup.java[tags=base_class,indent=0]
----
====

TIP: You need not specify the output directory for the generated snippets (since version 1.2.0.RELEASE of Spring REST Docs).

[[how-to-use-stubs-from-a-location]]
== How Can I Use Stubs from a Location

If you want to fetch contracts or stubs from a given location without cloning a repository or fetching a JAR, use the `stubs://` protocol when providing the repository root argument for Stub Runner or the Spring Cloud Contract plugin. You can read more about this in <<project-features.adoc#features-stub-runner-stubs-protocol, this section>> of the documentation.

[[how-to-generate-stubs-at-runtime]]
== How Can I Generate Stubs at Runtime

If you want to generate stubs at runtime for contracts, switch the `generateStubs` property in the `@AutoConfigureStubRunner` annotation, or call the `withGenerateStubs(true)` method on the JUnit Rule or Extension. You can read more about this in <<project-features.adoc#features-stub-runner-generate-stubs-at-runtime, this section>> of the documentation.

[[how-to-use-the-failonnostubs-feature]]
== How Can I Make The Build Pass if There Are No Contracts or Stubs

If you want Stub Runner not to fail if no stubs were found, switch the `generateStubs` property in the `@AutoConfigureStubRunner` annotation or call the `withFailOnNoStubs(false)` method on the JUnit Rule or Extension. You can read more about this in <<project-features.adoc#features-stub-runner-fail-on-no-stubs, this section>> of the documentation.

If you want the plugins not to fail the build when no contracts were found, you can set the `failOnNoStubs` flag in Maven or call the `contractRepository { failOnNoStubs(false) }` closure in Gradle.

[[how-to-mark-contract-in-progress]]
== How Can I Mark that a Contract Is in Progress

If a contract is in progress, it means that the, on the producer side, tests are not generated, but the stub is generated. You can read more about this in <<project-features.adoc#contract-dsl-in-progress, this section>> of the documentation.

In a CI build, before going to production, you would like to ensure that no in-progress contracts are on the classpath, because they may lead to false positives. For this reason, by default, in the Spring Cloud Contract plugin, we set the value of `failOnInProgress` to `true`. If you want to allow such contracts when tests are to be generated, set the flag to `false`.
