This presentation covers basics of RESTful webservices. I have prepared it by reading different online tutorials. One of them is java brains video tutorial. Hope this helps some one. If any one needs examples mentioned in the slides, please contact me.

1. S U R I N D E R K U M A R M E H R A
7 T H S E P T , 2 0 1 5
For "REST“, keep watching. For others,
Open Rest.
RESTFul Web Services

2. Outline
 Introduction
 REST and HTTP
 Resource Types
 Base URL
 HTTP Methods
 Method Idempotence
 HATEOAS
 Richardson Maturity
Model
 Path and Query Params
 Pagination and Filtering
 Sub Resources
 Exceptions
 Content Negotiation

3. Introduction
 REpresentational State Transfer (REST)
 An architectural Style
 Coordinated set of constraints to
distributed hypermedia system components design
 REST+Web Services = RESTFul Web Services
 Web sites use HTML with format and styling
 Meant for human consumption
 REST use XML/JSON without styling- bare bone
data
 Meant of Developers to use and style accordingly
 Has specific URL for each operation
 Just like static web page web sites

4. Introduction Contd…

5. Characteristics of Web Services
 Communication always happens over Web/HTTP
 Protocols:
 SOAP Web services: SOAP format
 REST: none… Can be XML/JSON/TEXT as long as client
server understand each other
 Data Exchange:
 SOAP: Always POST
 REST: Different methods for different purpose
 Service definition:
 SOAP: WSDL
 REST: None

6. Why No Rules in REST
 SOAP WS follow SOAP Web service Specification
 If SOAP WS does no follow even one rule , its not SOAP WS
 Committee maintains the rules
 REST is a concept introduced by Roy Fielding
 There is no committee to make rules

7. Why REST
• Used when lot of tiny data is needed
• Easy to build- No toolkit required
• Light weight- NO xml markup
• Independence- no strict rules like SOAP
• For bulk operations like detailed purchase order may not be
possible with REST

8. Little bit about HTTP
 HTTP: Hyper Text Transfer Protocol
 HTTP is a way to transfer/exchange hypertext
 Hypertext is a structured text which contains logical links to
other text.
 Logical links are called hyperlinks
 A common way to write hyper text is HTML
 HTML: Hyper Text Markup Language

9. HTTP Status Codes
 1XX - Informational
 2XX – Success
 3XX – Redirectional
 4XX – Client Error
 5XX – Server Error

10. HTTP & REST
 Address Resource Locations:
 Web sites use action based URI’s
 weatherapp.com/weatherLookup.do?zipcode=1234
 REST uses resource based URI’s
 weatherapp.com/zipcode/1234
 weatherapp.com/cities/Bengaluru
 Methods: GET, PUT , POST, DELETE
 Metadata:
 Status Codes: Defines status of response received
 Message Headers: type of data sent/received
Roy Fielding was one of the principal authors of HTTP Specification

11. Resource Types
 Instance Resources
 http://localhost:8081/messenger/webapi/messages/1
 Collection Resources
 http://localhost:8081/messenger/webapi/messages/

12. HTTP Methods
 GET
 PUT
 POST
 DELETE
 Few others

13. Method Idempotence
Idempotence :
Resource state on server is same before and after the
operation with same data
 PUT and DELETE are idempotent
 GET is Safe and therefore Idempotent
 POST is not idempotent
• Why ?

14. HATEOAS
 Hypermedia
 As
 The
 Engine
 Of
 Application
 State
 In short provides dynamic current Application state

15. Richardson Maturity Model
 Level 0: Swamp Of POX(Plain Old XML)
 Uses one entry point and one method-SOAP
 Level 1: Resource URI’s
 Individual URI’s for each resource and one method
 Level 2: HTTP Methods
 Uses the right HTTP method and status codes
 Level 3: HATEOAS
 Response have links that client can use further

16. Annotations
 @Path
 @Produces
 @Consumes
 @PathParam
 @Context
 @HeaderParam

17. Pagination & Filtering
 @QueryParam: Apply to request as a whole
 @MatrixParam: Apply to path element
 @BeanParam: Useful when lot of params are
needed.
Collection Resource supports query params:
 Offset
 Limit
…/messages?offset=50&limit=25

18. Sub Resources
@Path(“/parentId/subresourcemapping”)
getSubResourceAPI(){}
• The path of parent resource becomes the Base URI for Sub
Resource

19. Status Codes and Location Headers
 Return proper Status Code in Response
 201 instead of 200 when POST is successful
 Send Location Headers in Response

20. Content Negotiation
 Accept Header: What do I accept
 Content- Type: What am I sending

21. Exceptions Handling
 Custom Exception Mapper
 Generics Exception Mapper
 WebApplicationException
 ClientErrorException- for error code 4XX
 RedirectionException – for error code 3XX
 ServerErrorException – for error code 5XX
 Specific classes for each of above categories

22. Thank You !