This document discusses REST, its origins and growth, how it is implemented using HTTP, and examples of representing resource states in XML and JSON formats. It describes how the WSO2 ESB provides support for REST by receiving, processing, and mediating REST calls, and how APIs can be defined in the ESB without additional code. The document also outlines how the WSO2 platform can be used to develop comprehensive API management solutions based on open standards.

1. REST and API Management
with
Hiranya Jayathilaka
Product Manager – WSO2 ESB

2. What is REST?
● REpresentational State Transfer
● Lightweight, Client­Server architecture
● Interactions are based on the transfer of
resource state representations
● Systems exchange state representations and
perform application state transitions
● Mostly implemented using HTTP but can be
based on other protocols

3. Origin and Growth
● First introduced by Roy Fielding in his doctoral
dissertation
● Developed in parallel with HTTP/1.1
● WWW is the largest known implementation of a
RESTful architecture
● Widely used in modern days as an alternative to
technologies like CORBA and SOAP

4. REST By Example...
● Learning Management System for a school
● A number of fundamental concepts
● Student
● Course
● Teacher
● In a RESTful design these concepts are likely to
become the 'resources' managed by the LMS

5. The 'Student' Resource State
● Name
● Index number
● Age
● Date of birth
● Contact information
● GPA
● ...

6. State Representation ­ XML

7. State Representation ­ JSON

8. Application State
● Applications have states
● Number of students in the system
● Number of associations between students and
courses
● Number of teachers
● Application state transitions may occur as a
result of a resource state transfer
● Application state can also be represented using
some data format or hyper text references

9. Representational State Transfer
● Clients and servers interact with each other by
exchanging
● Resource state representations
● Application state representations
● Other control information

10. RESTful Interactions

11. Why HTTP?
● Rich vocabulary and powerful tools that are
ideal for representing resource states,
application states and control data
● Application state – Status code + Links
● Resource state – HTTP entity
● Control data – HTTP method
● CRUD operations map nicely into HTTP
methods

12. HTTP Based RESTful Interactions

13. Advantages
● Simple and lightweight
● Easy to implement
● Very little processing at the application level
● Small amount of data to pass around
● Support any content type
● Leverage built­in application layer protocol
semantics without reinventing the wheel

14. Notable Deployments
● Amazon AWS (Over 90% of the clients are
using the RESTful API)
● Google Maps
● Yahoo!
● eBay
● Sastry Malladi on service orientation ­
http://www.youtube.com/watch?v=O­9osZGXDok

15. WSO2 ESB
● A lightweight, high­performance ESB
● Feature rich and standards compliant
● SOAP and WS­* standards
● REST support
● Variety of protocols and message formats
● User friendly and highly extensible
● 100% free and open source with commercial
support

16. Under the Hood
● WSO2 ESB is based on a number of well
known Apache projects
● Synapse ­ http://synapse.apache.org
● Axis2­ http://axis.apache.org/axis2/java/core
● Web Services ­ http://ws.apache.org
● REST support of WSO2 ESB stems from the
REST support offered by Axis2

17. REST Support in Axis2
● Axis2 provides a REST binding for each
deployed web service
● This enables clients to invoke any Axis2 service
via REST calls
● GET /services/HelloService/sayHello
● GET /services/MathService/add?a=5&b=10

18. REST Support in WSO2 ESB
● WSO2 ESB can receive and mediate REST
calls just like any other request
● The same mediators that work with SOAP can
be used to manipulate REST invocations
● Log, Send, Filter, Switch, XSLT, DBLookup....
● Additional handles provided by the ESB in the
form of properties
● Easily switch between SOAP and REST

19. Exposing a SOAP Service via REST

20. Sample Proxy Configuration

21. Exposing a REST/POX Service via
SOAP

22. Sample Proxy Configuration

23. Exercising More Control Over REST
● Manipulate REST calls based on
● HTTP method
● Status code
● Content type
● HTTP headers

24. Accessing HTTP Method

25. Examples

26. Accessing HTTP Status Codes

27. Examples

28. Manipulating HTTP Headers

29. Examples

30. REST APIs
● An API is similar to a web application hosted on
the ESB
● Anchored at a specific URL path (context)
● /test
● /dictionary
● /foo/bar
● Can be bound to a specific host and a port
● Contains one or more resources

31. Resources
● A RESTful resource exposed over HTTP
● Similar to a proxy service but focuses on REST
● Can be associated with
● A set of HTTP methods
– GET only, GET and POST only, All HTTP methods
● A specific content type
– application/xml, application/json
● A particular class of clients (user agents)

32. Dispatching Requests to a Resource
● URL patterns
● Reg­Ex match (/test/*)
● Extension match (*.jsp)
● Exact match (/test/index.jsp)
● URI templates
● /dictionary/{character}/{word}
● /accounts/{accountId}/{operation}

33. APIs and Resources

34. Resource Examples

35. API Example

36. APIs in Action

37. API Management Goals
● Service provider objectives
● Define APIs
● Define security requirements and SLAs
● Monitor API usage and SLAs
● Service consumer objectives
● Discover and browse APIs
● Sign up and obtain API keys
● Consume APIs using the obtained keys
● Monitor API usage and SLAs

38. Solution Architecture

39. WSO2 Product Mapping

40. Summary and Recap
● REST is a lightweight, client­server architecture for building
distributed systems
● RESTful designs are concerned with resources, states and
transfer of representational state between systems
● WSO2 ESB provides excellent support for receiving, processing
and intermediating REST (HTTP) calls
● The new API concept is a powerful feature which allows
developers to define REST APIs in the ESB without writing any
additional code
● WSO2 platform is ideally suited for developing comprehensive and
flexible API management solutions based on open standards

41. Questions?

42. Selected Customers

43. WSO2 Engagement Model
● Quick Start
● Development Support
● Development Services
● Production Support
● Turnkey Solutions
● WSO2 Mobile Services Solution
● WSO2 FIX Gateway Solution
● WSO2 SAP Gateway Solution

44. Thank You