Javantura v4 - True RESTful Java Web Services with JSON API and Katharsis - Matija Dujmović
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1) The document discusses REST (Representational State Transfer), its constraints, and the Richardson Maturity Model for classifying RESTful web services. 2) It introduces JSON API as a standard for building RESTful hypermedia APIs and describes how the Katharsis library implements JSON API in Java applications. 3) An example is provided of using Spring Boot and Katharsis to build a RESTful web service with a Project and Task domain that follows the JSON API standard.
Javantura v4 - True RESTful Java Web Services with JSON API and Katharsis - Matija Dujmović
- 1. True RESTful Java Web Services with JSON API and Katharsis MATIJA DUJMOVIĆ (NEOS) ALEKSANDER RADOVAN (KING ICT)
- 2. What is REST? Representational State Transfer An architectural style defined by Roy Fielding in his doctoral dissertation, described by six constraints Resource-based Uses representations Protocol and media type agnostic
- 3. Richardson Maturity Model 1/3 A convenient model to help explain the specific properties of REST Divided into four levels Each higher level represents a more mature REST API with only the last level representing a true REST API
- 4. Richardson Maturity Model 2/3
- 5. Richardson Maturity Model 3/3 Level 0: Swamp of POX ◦ Uses the HTTP protocol just as a transport layer through the HTTP POST method ◦ e.g. SOAP Level 1: Resources ◦ Clearly distinguishes between resources but still uses only the HTTP POST method ◦ e.g. http://example.com/api/projects/123 represents a project resource with id 123 Level 2: HTTP verbs ◦ uses all HTTP verbs (GET for reading, POST for creating, PUT or PATCH for updating and DELETE for deletion) Level 3: Hypermedia ◦ Uses HATEOAS to deal with discovering the possibilities of your API towards the clients ◦ API-s that conform to this level are often called Hypermedia API-s
- 6. HATEOAS Hypermedia As The Engine Of Application State A constraint of the REST architectural style By correctly using a hypermedia type in your REST API you are implicitly using HATEOAS Let’s explain it by examining an API that uses a hypermedia type!
- 7. Hypermedia types 1/2 "Hypermedia Types are MIME media types that contain native hyper-linking semantics that induce application flow. For example, HTML is a hypermedia type; XML is not." Hypermedia APIs with HTML5 & Node, Mike Amundsen (2010) "The WWW is fundamentally a distributed hypermedia application.” Software Architecture: Foundations, Theory and Practice, Taylor, Medividovic, Dashofy (2010) JSON isn’t a hypermedia type because it doesn’t have built-in support for hyperlinks The REST architectural style is based on the architecture of the WWW.
- 9. JSON API Created by Yehuda Katz, started drafting in 2013 and finalized in 2015 JSON API is the only media type that is currently a living standard Actively used in the Ember.js JavaScript framework Supported in Java with the Katharsis framework!
- 10. Example domain and API The API endpoint is http://localhost:8080/api/ , only the changing part of the URI will be shown in examples The example domain is made of Project and Task objects A Project object can have many Task objects A Task object can have only one Project object
- 11. JSON and JSON API comparison
- 12. JSON API related URI
- 13. JSON API include relationship
- 14. JSON API using only one field
- 15. JSON API self URI
- 16. Katharsis The Katharsis library adds an additional layer on top of RESTful endpoints to provide easy HATEOAS support for Java by implementing the JSON API standard Standard server-side framework integration ◦ Spring Boot ◦ Servlet ◦ JAX-RS (Java API for RESTful Web Services) ◦ Hibernate Also offers a Java client for JSON API
- 17. Spring Boot and Katharsis 1/6 Project structure
- 18. Spring Boot and Katharsis 2/6 application.properties
- 19. Spring Boot and Katharsis 3/6 ExampleApplication.java
- 20. Spring Boot and Katharsis 4/6 Project.java , excluded getters, setters and constructors for readability
- 21. Spring Boot and Katharsis 5/6 ProjectRepository.java @JsonApiFindOne -> GET projects/123 @JsonApiFindAll -> GET projects @JsonApiFindAllWithIds -> GET projects/123,124 @JsonApiDelete -> DELETE projects/123 @JsonApiSave -> POST projects , PATCH projects/123
- 22. Spring Boot and Katharsis 6/6 ProjectToTaskRepository.java , implements the relationship endpoint e.g.
- 23. Alternatives http://projects.spring.io/spring-hateoas/ , hypermedia support with link building features http://elide.io/ , quick JSON API endpoint development for JPA entities
- 24. More information http://amundsen.com/hypermedia/ , Mike Amundsen’s page explaining hypermedia http://katharsis.io/ , Katharsis project homepage http://jsonapi.org/ , JSON API homepage https://gtramontina.github.io/h-factors/ , visualization of available hypermedia and it’s features Mike Amunden, Build Hypermedia APIs with HTML5 and Node, O’Reilly, 2010
- 25. Questions?
- 26. Thank you!