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sullis
December 10, 2019
Programming
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OpenAPI and Java - Portland - 2019-12-10
Portland Java User Group
Portland Oregon
December 10, 2019
#openapi
#java
sullis
December 10, 2019
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Transcript
OpenAPI and Java Sean Sullivan Portland Java User Group December
10, 2019
About me software engineer Portland Oregon Java Scala
Agenda OpenAPI Real world examples Java tools and libraries API
guidelines
OpenAPI
OpenAPI is a specification for describing API’s
API specifications
WSDL (SOAP) WADL (REST)
Swagger (REST) OpenAPI (REST)
https://en.wikipedia.org/wiki/OpenAPI_Specification
REST API’s
API Driven Development
“API first”
source: Adobe Tech Blog June 2017
Code first vs API schema first
JSON or YAML
Real world examples
Case Study: stripe.com OpenAPI
https://github.com/stripe/openapi
https://github.com/stripe/openapi
Case Study: squareup.com OpenAPI
https://github.com/square/connect-api-specification
Case Study: Kubernetes OpenAPI
https://github.com/kubernetes/kubernetes/tree/master/api/openapi-spec
https://github.com/kubernetes-client/java Kubernetes Java Client
https://github.com/kubernetes-client/java Kubernetes Java Client code generation
Case Study: Microsoft Azure OpenAPI
https://github.com/Azure/azure-rest-api-specs azure-rest-api-specs
Case Study: Amazon EventBridge OpenAPI
https://docs.aws.amazon.com/eventbridge Amazon EventBridge “EventBridge is a serverless event bus service
that makes it easy to connect your applications with data from a variety of sources”
https://docs.aws.amazon.com/eventbridge EventBridge Schema Registry Schemas are defined using JSON files,
using the OpenAPI specification
https://www.tbray.org/ongoing/When/201x/2019/12/02/Strongly-Typed-Events Strongly typed events
Java tools and libraries
Swagger libraries swagger-core swagger-parser swagger-codegen swagger-inflector
https://github.com/swagger-api/swagger-parser Swagger parser
pom.xml <dependency> <groupId>io.swagger.parser.v3</groupId> <artifactId>swagger-parser</artifactId> <version>2.0.16</version> </dependency> Swagger parser
https://github.com/swagger-api/swagger-parser import io.swagger.v3.parser.OpenAPIV3Parser; import io.swagger.v3.oas.models.OpenAPI; String url = “http://petstore.swagger.io/v3/openapi.json”; OpenAPI
openAPI = new OpenAPIV3Parser().read(url); Swagger parser
https://github.com/swagger-api/swagger-parser Swagger parser Pull Request #1271
ObjectMapperFactory.java return new JsonFactoryBuilder() .enable(StreamReadFeature.STRICT_DUPLICATE_DETECTION) .build(); Swagger parser Pull Request
#1271
Code generators Guardrail openapi-generator swagger-codegen AutoRest
Guardrail project
https://guardrail.dev/ Guardrail
https://github.com/twilio/guardrail Guardrail
https://github.com/twilio/guardrail Guardrail: Scala ScalaMeta
https://github.com/twilio/guardrail Guardrail: Java JavaParser
Guardrail example
guardrail-maven-plugin <plugin> <groupId>com.twilio</groupId> <artifactId>guardrail-maven-plugin_2.12</artifactId> <version>0.54.5</version> <executions> … </executions> </plugin>
guardrail-maven-plugin <configuration> <language>java</language> <kind>client</kind> <framework>dropwizard</framework> <specPath>${project.basedir}/src/main/openapi/petstore.json</specPath> <packageName>com.example.clients.petstore</packageName> </configuration> Java client
guardrail-maven-plugin
openapi-generator project
openapi-generator
openapi-generator
openapi-generator
REST API guidelines
https://github.com/microsoft/api-guidelines
https://www.infoq.com/news/2016/07/microsoft-rest-api/ July 2016
https://cloud.google.com/apis/design/
https://github.com/zalando/restful-api-guidelines
https://github.com/paypal/api-standards/blob/master/api-style-guide.md
Final thoughts use OpenAPI to define REST API’s adopt “API
First” approach use a code generator to generate client libraries contribute to open source projects
The End