Tuesday, 7 March 2017

REST / RESTful Web Service Interview Questions - Part 1

What REST stands for?
REST stands for REpresentational State Transfer.

What is REST?
REST is web standards based architecture and uses HTTP Protocol for data communication. It revolves around resource where every component is a resource and a resource is accessed by a common interface using HTTP standard methods. REST was first introduced by Roy Fielding in 2000.
In REST architecture, a REST Server simply provides access to resources and REST client accesses and presents the resources. Here each resource is identified by URIs/ global IDs. REST uses various representations to represent a resource like text, JSON and XML. Now a days JSON is the most popular format being used in web services.

Name some of the commonly used HTTP methods used in REST based architecture?
Following well known HTTP methods are commonly used in REST based architecture −
GET − Provides a read only access to a resource.
PUT − Used to create a new resource.
DELETE − Ued to remove a resource.
POST − Used to update a existing resource or create a new resource.
OPTIONS − Used to get the supported operations on a resource.




What is web service?
A web service is a collection of open protocols and standards used for exchanging data between applications or systems. Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet in a manner similar to inter-process communication on a single computer.

What are RESTful webservices?
Web services based on REST Architecture are known as RESTful web services. These web services use HTTP methods to implement the concept of REST architecture. A RESTful web service usually defines a URI, Uniform Resource Identifier a service, provides resource representation such as JSON and set of HTTP Methods.

What is a Resource in REST?
REST architecture treats every content as a resource. These resources can be text files, html pages, images, videos or dynamic business data. REST Server simply provides access to resources and REST client accesses and modifies the resources. Here each resource is identified by URIs/ global IDs.

How to represent a resource in REST?
REST uses various representations to represent a resource where text, JSON, XML. XML and JSON are the most popular representations of resources.

What are the best practices to design a resource representation?
Following are important points to be considered while designing a representation format of a resource in a RESTful web services −
Understandability − Both Server and Client should be able to understand and utilize the representation format of the resource.
Completeness − Format should be able to represent a resource completely. For example, a resource can contain another resource. Format should be able to represent simple as well as complex structures of resources.
Linkablity − A resource can have a linkage to another resource, a format should be able to handles such situations.

Which protocol is used by RESTful webservices?
RESTful web services make use of HTTP protocol as a medium of communication between client and server.

What is messaging in RESTful webservices?
A client sends a message in form of a HTTP Request and server responds in form of a HTTP Response. This technique is termed as Messaging. These messages contain message data and metadata i.e. information about message itself.


What is addressing in RESTful webservices?
Addressing refers to locating a resource or multiple resources lying on the server. It is analogous to locate a postal address of a person.

What is URI?
URI stands for Uniform Resource Identifier. Each resource in REST architecture is identified by its URI.

What is purpose of a URI in REST based webservices?
Purpose of an URI is to locate a resource(s) on the server hosting the web service.

What is format of a URI in REST architecture?
A URI is of following format −
<protocol>://<server-address:port>/<service-name>/<ResourceType>/<ResourceID>

What is the purpose of HTTP Verb in REST based webservices?
VERB identifies the operation to be performed on the resource.

What are the best practices to create a standard URI for a web service?
Following are important points to be considered while designing a URI −
Use Plural Noun − Use plural noun to define resources. For example, we've used users to identify users as a resource.
Avoid using spaces − Use underscore(_) or hyphen(-) when using a long resource name, for example, use authorized_users instead of authorized%20users.
Use lowercase letters − Although URI is case-insensitive, it is good practice to keep url in lower case letters only.
Maintain Backward Compatibility − As Web Service is a public service, a URI once made public should always be available. In case, URI gets updated, redirect the older URI to new URI using HTTP Status code, 300.
Use HTTP Verb − Always use HTTP Verb like GET, PUT, and DELETE to do the operations on the resource. It is not good to use operations names in URI.



What is statelessness in RESTful Webservices?
As per REST architecture, a RESTful web service should not keep a client state on server. This restriction is called statelessness. It is responsibility of the client to pass its context to server and then server can store this context to process client's further request. For example, session maintained by server is identified by session identifier passed by the client.

What are the advantages of statelessness in RESTful Webservices?
Following are the benefits of statelessness in RESTful web services −
·         Web services can treat each method request independently.
·         Web services need not to maintain client's previous interactions. It simplifies application design.
·         As HTTP is itself a statelessness protocol, RESTful Web services work seamlessly with HTTP protocol.

What are the disadvantages of statelessness in RESTful Webservices?
Following is the disadvantage of statelessness in RESTful web services −
·         Web services need to get extra information in each request and then interpret to get the client's state in case client interactions are to be taken care of.

What do you mean by idempotent operation?

Idempotent operations means their result will always same no matter how many times these operations are invoked.


Refer to Part 2 of the interview questions set at below URLhttp://osb-dheeraj.blogspot.in/2017/03/rest-restful-web-service-interview.html



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