This document discusses REST APIs using Java (JAX-RS) and Jersey. It provides an overview of REST concepts and the JAX-RS and Jersey frameworks. It demonstrates how to create a basic Jersey project in Eclipse and implement CRUD operations. It also discusses using Swagger to generate documentation for RESTful APIs from JAX-RS annotations.

1. By NeeravArora (Cerner Healthcare Solutions Pvt Ltd.)
&
Kumaraswamy M (IBM)
REST with Java (JAX-RS) and Jersey

2. Agenda
 Rest API concepts .
 Foundation .
 JAX-RS and Jersey .
 Setting up Jersey project in eclipse.
 JAX-RS annotations .
 CRUD app.
 Restful API’s with Swagger.

3. Rest API Concepts
 Services exposed to internet for programmatic access
 Users can be either producers or consumers or both
 Eg : api.twitter.com
 Data can be returned in the form of XML /JSON / etc
 Helps developers to parse data.
 Messages can be exchanged in any kind of HTTP method

4. Foundation
Nouns (Resources)
unconstrained
i.e., http://example.com/employees/12345
Representations
constrained
i.e., XML
Verbs
constrained
i.e., GET

5. Resources
 REST uses URI to identify resources .
 http://localhost/books/
 http://localhost/books/ISBN-0011
 http://localhost/books/ISBN-0011/authors
 http://localhost/classes
 http://localhost/classes/cs2650
 http://localhost/classes/cs2650/students
 As you traverse the path from more generic to more
specific, you are navigating the data .

6. Action/Verb
 /orders
 GET - list all orders
 POST - submit a new order
 /orders/{order-id}
 GET - get an order representation
 PUT - update an order
 DELETE - cancel an order
 /orders/average-sale
 GET - calculate average sale
 /customers
 GET - list all customers
 POST - create a new customer
 /customers/{cust-id}
 GET - get a customer representation
 DELETE- remove a customer
 /customers/{cust-id}/orders
 GET - get the orders of a customer

7. Representations (MediaType)
 XML
<COURSE>
<ID>CS2650</ID>
<NAME>Distributed Multimedia Software</NAME>
</COURSE>
 JSON
{“course”: {
“id”: “CS2650”
“name”: “Distributed Multimedia Software”
}
}

8. Why it is called “REST” ?

9. JAX-RS
 Java API for RESTfulWeb Services .
 Provides support in creating web services according to the
Representational StateTransfer (REST) architectural pattern .
 Uses annotations .

10. Jersey
 One of the libraries that implements JAX-RS , from Oracle.
 Other libraries in the market -
* Apache CXF , an open sourceWeb service framework .
* RESTeasy, JBoss 's implementation .
* Restlet .
* ApacheWink ,Apache Software Foundation Incubator .
*WebSphereApplication Server from IBM.
 Choice of library doesn’t matter .

11. Big Picture

12. Big Picture (contd…)

13. Your first Jersey project

14. Your first Jersey project (contd…)

15. http://repo1.maven.org/maven2/archetype-catalog.xml
Your first Jersey project (contd…)

16. Your first Jersey project (contd…)

17. Your first Jersey project (contd…)

18. Your first Jersey project (contd…)

19. Root resource class

20. @Path
Sets the path to base URL + /your_path.The base URL is based on your application name,
the servlet and the URL pattern from the web.xml configuration file.

21. @GET, @PUT, @POST, @DELETE, ...

22. @Produces
@Produces defines which MIME type is delivered by a method annotated with @GET. In
the example text ("text/plain") is produced. Other examples would be "application/xml"
or "application/json"

23. @PathParam
Used to inject values from the URL into a method parameter.This way you inject,
for example, the ID of a resource into the method to get the correct object.

24. @Consumes
@Consumes defines which MIME type is consumed by this method.

25. CRUD App example (Model)

26. CRUD App example (Model)

27. CRUD App example (Database)

28. CRUD App example (Service)

29. Crud App (Resource)

30. RESTFul APIs with Swagger

31. What is Swagger and Why Swagger?
• Simple representation of your RESTFul API
• Declarative resource specification
• JSON specification
• Swagger UI to interact with the API in a sandbox UI
• Why Jersey Client / JUNIT for your client or boss?
• Developers and documentation… hahaha
• Support your existing RESTFul API without change

32. Swagger Specification
• Resource Listing
• API Description
Create Swagger Specification
• Codgen - converts annotations in your code into swagger
specification
• Manually - writing the JSON by hand

33. Swagger Specification

35. References
• http://www.vogella.com/tutorials/REST/article.html
• https://jersey.java.net/documentation/latest/jaxrs-
resources.html
• https://github.com/koushikkothagal/messenger
• http://swagger.io/specification/
• https://github.com/swagger-api/swagger-spec
• https://github.com/swagger-api/swagger-core
• http://petstore.swagger.io/