PACT Consumer Driven Contracts Spring Boot example
PACT is a contract testing tool.
It helps to test communications between services/microservices.
But the main idea of this repository is different.
This is manual how to use PACT Broker with Maven in Spring Boot.
If you want more information about PACT - follow next docs.
Consumer - A client that wants to receive some data.
Here is an example of how consumer share pact files on broker:
<plugin><groupId>au.com.dius</groupId><artifactId>pact-jvm-provider-maven_2.12</artifactId><version>3.5.11</version><executions><execution><phase>install</phase><goals><goal>publish</goal></goals><!-- Run broker on local machine with docker using docker-compose file --><configuration><pactDirectory>${basedir}/target/pacts</pactDirectory><pactBrokerUrl>http://localhost:80</pactBrokerUrl><projectVersion>1.1</projectVersion></configuration></execution></executions></plugin>
Consumer test generate json in target file, when it exetutes via Spring Boot context. And next step on maven plugin, which share this json on broker. It’s pretty easy and can be executed in CI Job.
Build Comsumer:
mvn clean install
Then run:
mvn spring-boot:run
Consumer application have swagger-ui is available on http://localhost:8080/swagger-ui.html
Example of Consumer interaction on broker:
Provider - a service or server that provides the data.
Provider must verify interaction from broker. If interaction succesfully verified - broker mark it via green color, if not - via red color.
For more info, read next part of documentation.
Build Provider:
mvn clean install
If you want to verify interaction on briker, first run application:
mvn spring-boot:run
And in additional terminal use plugin to verify:
mvn pact:verify
It’s important, because naven plugin for verify PACT works upon of Spring Boot application context.
The oddity is that when performing Spring Boot tests with a raised context, the consumer still takes the JSON from the broker. Only except for the fact that he does not mark them as “verified”.
Provider application have swagger-ui is available on http://localhost:7073/swagger-ui.html
The Pact Broker is an application for sharing for consumer driven contracts and verification results. It is optimised for use with “pacts” (contracts created by the Pact framework), but can be used for any type of contract that can be serialized to JSON.
More info available here.
For example.
We can use HTTP REST calls to broker. You most likely won’t need to get your hands dirty with curl however, as pact publishing is built in to most of the native pact libraries already.
For example:
cd Consumer
In console use next cUrl:
curl -v -XPUT -H "Content-Type: application/json" -d@foo-bar.json http://localhost:80/pacts/provider/Bar/consumer/Foo/version/1.0.0+4jvh387gj3
Just use docker compose:
docker-compose --file docker-compose-pact.yaml up --build
And then open:
http://localhost:80
In this example swagger definition used for API generation. Here we generate YAML swagger definition for Provider (swagger file located in target folder):
<plugin><groupId>com.github.kongchen</groupId><artifactId>swagger-maven-plugin</artifactId><version>3.1.7</version><configuration><apiSources><apiSource><springmvc>true</springmvc><locations><location>com.slandshow.demo</location></locations><outputFormats>yaml</outputFormats><schemes><scheme>http</scheme></schemes><info><title>PACT Provider</title><version>1.0</version><description>Nothing</description></info><swaggerDirectory>${basedir}/target/swagger/temp</swaggerDirectory><swaggerApiReader>com.github.kongchen.swagger.docgen.reader.SpringMvcApiReader</swaggerApiReader><swaggerFileName>internal-swagger</swaggerFileName></apiSource></apiSources></configuration><executions><execution><configuration><apiSources><apiSource><locations><location>com.slandshow.demo</location></locations><swaggerFileName>internal-swagger</swaggerFileName></apiSource></apiSources></configuration><id>internal-generation</id><phase>compile</phase><goals><goal>generate</goal></goals></execution></executions></plugin>
And in Consumer we generate code via maven plugin according on this YAML swagger file:
<plugin><groupId>io.swagger</groupId><artifactId>swagger-codegen-maven-plugin</artifactId><version>2.2.3</version><executions><execution><id>generate-swagger-javaclient</id><goals><goal>generate</goal></goals><configuration><!-- In enterprise projects this swagger yaml specification must be verified from Nexus--><!-- But here it just hardcored --><inputSpec>${basedir}/src/main/resources/api.yaml</inputSpec><language>java</language><generateApiTests>false</generateApiTests><generateModelTests>false</generateModelTests><library>resttemplate</library><modelPackage>${project.groupId}.client.model</modelPackage><apiPackage>${project.groupId}.client.api</apiPackage><invokerPackage>${project.groupId}.client.invoker</invokerPackage><importMappings><importMapping>ByteArrayResource=org.springframework.core.io.ByteArrayResource</importMapping></importMappings><configOptions><dateLibrary>java8-localdatetime</dateLibrary></configOptions></configuration></execution></executions></plugin>
So, Provider generates RestTemplate api for Consumer. We can invoke Provider from Consumer using this generated client api. This is a main idea for communication between two microservices.