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Introduction In this modern world, enterprises are in the need of implementing Service Oriented Architecture (SOA) to achieve maximum business benefits
SOAP/WSDL/UDDI - SOA stack is the most common way and have failed to live up to their promise in some cases
Due to the complexity and high cost, enterprises are looking at alternatives to build their integration architecture in a simpler way.
In order to achieve low-cost, flexible integration, increased data security, and greater scalability, there is tremendous interest in REpresentational State Transfer (REST) architectural style 4<br>
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What is REST? REST stands for “REpresentational State Transfer”, was introduced and defined in 2000 by the doctoral dissertation of Roy Fielding
REST is an architectural style which has set of constraints that can be applied on networking architecture to create RESTful architecture typically, on client server architecture. 5<br>
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How does REST work? … REST Hyperlink to a resource and the only way of exchange data between client and server
Each resource can be accessed by unique ID called URI
Example:
<domain>/depts/
<domain>/depts/finance
<domain>/employees/senthil Representation is a temporal state of the actual data
Representation is sent back and forth between client and server
Example: XML, JSON, Text Resources can be anything, simple entity or entities
Actual data of the system and can be in any form
Example: Customer, Orders etc<br>
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… How does it work? REST in action
In REST URIs are used to connect clients and servers to exchange resources in the form of representations
In order to exchange data, REST relies on basic HTTP protocol methods: GET, POST, PUT and DELETE.
Accept header is
used for representation
HTTP method is
used for operation
URI is used to
locate resources 7 1 2 3 1 2 3<br>
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… How does it work? REST in detail (GET/RETRIEVE)
The method GET is used to RETRIEVE resources.
Client application makes a HTTP request with the method type GET and Senthil as the identifier
The representation type is set
through the Accept request header
REST Framework invokes
domain code to retrieve
data and to generate
Representation in XML
Servlet container sends back the
response as XML with 200 as
the status code 8<br>
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RESTful Architecture A typical Java based RESTful architecture consists of 3 layers.
The Restful Service layer intercepts incoming http requests to identify the representation, resource and the operation
JAX-RS is the
specification defined by
Sun to create and use
RESTful services in
Java applications.
The Business Layer uses appropriate
framework to execute the business logic.
The Data Layer is responsible for
data logic and takes care of O/R mapping. 9<br>
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REST vs SOAP? Lightweight – easy to develop, no toolkits are required, works based on fundamental principles of HTTP and no contracts involved.
SOAP is complex, it requires greater implementation effort and understanding on the client side and server side.
The XML metadata information and SOAP headers associated with web services are considered to be an overhead than the HTTP headers.
HTTP itself is providing all facilities for an efficient, secured consumption of business logic and data, so SOAP and WS-* are considered overhead.
The stateless, highly scalable RESTful services are adopted in major key players such as Google, Amazon, Microsoft, Digg, Flickr and Twitter 10<br>
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Why and When? Consider REST:
REST may be considered if the service model is light, stateless, low cost, which requires improved data security and high scalability
Consider SOAP:
REST does not enforce any service contract, if the service model requires stronger service contract between server and client, REST may not be an option.
Some of the SOAP capabilities such as transaction, policy are not standardized in REST
REST operates on stateless model, which may not be friendly for stateful service model 11<br>
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12 Part II
REST Deep Dive<br>
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JAX-RS JAX-RS (Java API for RESTful Web Service)
JAX-RS provides support in creating Web Services according to the REST architectural style.
Simple, Annotation based, introduced in Java SE5 for the development and deployment of web services and clients.
Some of the Implementations of JAX-RS:
Apache CXF, Sun’s Jersey, Jboss’s RESTEasy, RESTlet, Apache Wink 13<br>
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Jersey Jersey is a reference implementation of JAX-RS by Sun Microsystems.
Jersey implements all the REST constraints as defined by Roy.
Jersey implements support for the annotations defined in JSR-311, making it easy for developers to build RESTful web services with Java and the Java JVM.
Uses JAXB for XML to Objects Binding
Integrates well with Spring framework
Supports WADL (Web Application Description Language). WADL is the REST equivalent for WSDL 14<br>
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REST – How to? … RESTful web service life cycle can be summarized in the following six steps:
1. Requirements Gathering
Similar to traditional requirements gathering, need to identify what the RESTful services should do.
2. Resource Identification
Similar to OOAD, need to identify list of objects to be used in services.
These are typical model objects used within RESTful services.
3. Resource representation definition
It is the representation of resources that are exchanged between clients and servers, so we should define what kind of representation we need to use.
Typically, we use XML, but JSON has gained popularity for its simplicity.
4. URI Definition
Consists of URIs for clients and servers to exchange resources representations 15<br>
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… REST – How to? 5. Implementation
Environment Setup: Eclipse, Tomcat6, Jersey, Dynamic Web project
Controller: Receives and processes incoming Restful requests. Use JAX-RS Annotations for URL based method invocations
EmployeeManager: Provides CRUD on Employees
DepartmentManager: Provides CRUD on Departments
SearchManager: Provides Search feature on employees and departments
Model: Resources whose representations are exchanged between the client and the server
Employee, Department
Business/Data Logic: Perform operations on underlying data.
StorageService: All data operations are on done using static HashMaps for demo purposes 16<br>
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… REST – How to? 6. Testing
Jersey Client API
Originally used for Jersey Unit testing, but applicable as a general RESTful client API
Provides a high level wrapper over low level CRUD operations on resources
Java Http Client
Jakarta Commons HttpClient provides an efficient and easy-to-use tool kit for HTTP request/response operations
Test Harness
Custom-built web application with a User interface to test RESTful Web services
Allows the user to select the “Accept” header, HTTP method, HTTP URL and the Request payload 17<br>
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Q & A Presentation and demo code can be downloaded from: www.collabera.com/SIJC.jsp Established in 1991, Collabera is a global, end-to-end information technology consulting and services company. With over 5000 professionals operating from 19 locations and 3 development centers worldwide, Collabera provides onsite, offsite and offshore services to global 2000 corporations.
For more information about the company, visit www.collabera.com<br>
