This document discusses how Spring Cloud Contract can help enable API evolution between a consumer and producer by allowing them to collaborate on contract tests. It describes how the consumer and producer each clone the code, with the consumer filing a pull request for a new interaction. The producer then takes over the pull request, implements the missing logic, and merges it. This allows the consumer to download the producer's stubs during its build to validate interactions. The document also addresses questions like storing contracts in a separate repository and using Rest Docs to generate stubs without writing scripts.

1. Consumer-Driven Contracts
to enable API evolution
Marcin Grzejszczak
Marcin Grzejszczak @mgrzejszczak, 17-19 May 2017

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Spring Cloud developer at Pivotal
Working mostly on
● Spring Cloud Sleuth
● Spring Cloud Contract
● Spring Cloud Pipelines
About me
Twitter: @mgrzejszczak
Blog: http://toomuchcoding.com

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Introduction
Demo
Summary
Agenda

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What we will NOT be talking about?

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What we will NOT be talking about?
THE IDEA OF SPRING CLOUD
CONTRACT IS NOT TO
INTRODUCE UNNECESSARY
COUPLING OR REPLICATE OLD
MISTAKES

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Introduction

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Introduction
What problems are we trying to solve?

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Introduction
Typical situation
HTTP
CONSUMER PRODUCER

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Introduction
How to write a test for it?
HTTP
CONSUMER PRODUCER

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Introduction
How to write a test for it?
HTTP
CONSUMER PRODUCER

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Introduction
Stub validity & reusability
WE’RE ON THE CONSUMER SIDE!!
CONSUMER OWNS THE STUB
DEFINITIONS

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Introduction
Stub validity & reusability

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Introduction
Let’s assume that we’re introducing a new
endpoint...

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Introduction
Stub validity & reusability

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Introduction
So now what?

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Introduction
Ooops...

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Introduction
What went wrong?
HTTP
CONSUMER PRODUCER
TEST
OK
HTTP
CONSUMER PRODUCER
REALITY
WAT?!

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Introduction
Another example with messaging
CONSUMERPRODUCER
TEST
PRODUCER CONSUMER
REALITY
topic: bar topic: foo
topic: bar

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Introduction
Stub validity & reusability

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Introduction
Nice API creation

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Introduction
Nice API creation - no cooperation results

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Introduction
Nice API creation - no cooperation results

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Demo
Potential answer
Spring Cloud Contract

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Demo
What are we going to code?

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Introduction
What are we going to code?
I’m 22 give me a beer
CONSUMER PRODUCER
THERE YOU GO
Can he get the beer?
Yes!

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Introduction
What are we going to code?
I’m 17 give me a beer
CONSUMER PRODUCER
GET LOST
Can he get the beer?
No!

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Demo
Who is who?
BLACK TERMINAL
BLACK IDE
CONSUMER
WHITE TERMINAL
WHITE IDE
PRODUCER

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Demo

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Demo
PRODUCER CONSUMER

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Demo
PRODUCER
CONSUMER
CLONES
PRODUCER
PRODUCER
CLONE CONSUMER

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Demo
PRODUCER CONSUMER
CONSUMER
CLONES
PRODUCER
PRODUCER
CLONE
INTERACTION

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Demo
PRODUCER CONSUMER
PRODUCER
CLONE
INTERACTION
CONSUMER FILES
A PR

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Demo

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Demo
PRODUCER
TAKES OVER THE PR

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Demo
PRODUCER
TAKES OVER THE PR
WRITES THE MISSING
IMPLEMENTATION

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Demo
PRODUCER
TAKES OVER THE PR
WRITES THE MISSING
IMPLEMENTATION
MERGES TO MASTER
CI UPLOADS TO NEXUS /
ARTIFACTORY

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Demo

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Demo
CONSUMER
SWITCHES TO
ONLINE MODE
DOWNLOADS STUBS OF
COLLABORATORS DURING
BUILD PHASE

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I don’t want to keep my contracts with the producer

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I don’t want to keep my contracts with the producer
You can keep the contracts
in a dedicated repository!

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Common repo with contracts
PRODUCER CONSUMERREPO WITH
CONTRACTS
INTERACTIONINTERACTION

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Summary

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Summary

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I don’t want to write any scripts!

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Spring Cloud Contract with Rest Docs
Don’t worry! You can use Spring Cloud
Contract WireMock with Rest Docs!!

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Spring Cloud Contract with Rest Docs - producer side

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● stubMatchers testMatchers
Summary

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Learn More. Stay Connected.
▪ Read the docs
http://cloud.spring.io/spring-cloud-contract/spring-cloud-contract.html
▪ Check the samples
https://github.com/spring-cloud-samples/spring-cloud-contract-samples
▪ Talk to us on Gitter
https://gitter.im/spring-cloud/spring-cloud-contract
Twitter: twitter.com/springcentral
YouTube: spring.io/video
LinkedIn: spring.io/linkedin
Google Plus: spring.io/gplus

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Survey
http://tiny.cc/geeconcdc

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QUESTIONS

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mgrzejszczak