Concepts of Web services

  • Web services is a way of communication between two software which is language inter operable. In simple terms it helps to use or link/exchange data between different applications and different platforms
  • Web services are application components which are self describing
  • Web services uses open protocols
  • XML + HTTP is the basic platform of Web services.
  • HTTP is the most used internet protocol. XML can be used between different platforms and programming languages.
  • Web services helps different applications to link their data
  • With its help we can exchange data between different applications and different platforms
  • Web services are reusable application components, it can be called and used by various Clients.
  • The Web services resides in a server which is connected to the Client through LAN/internet. This server is called service provider and the Client is the service consumer.
  • Web services are of two types: 1) SOAP based 2) REST based

  • SOAP is a lightweight protocol intended for exchanging structured information in a decentralized, distributed environment. SOAP uses XML technologies to define an extensible messaging framework, which provides a message construct that can be exchanged over a variety of underlying protocols. The framework has been designed to be independent of any particular programming model and other implementation- specific semantics.
  • SOAP allows to go around firewalls and is developed as per W3C standard
  • Rest is set of guidelines as to how Client should interact with the Restful Web services server
  • Rest guidelines says data and functionality which Client can access on the server is known as a resource and each resource should be accessed using its URI by all the Clients.
  • Client sends request for a resource, the server sends a response which is a representation of the resource. The resource can be presented in multiple formats like HTML, XML, Plain text, PDF, JPEG, etc.
  • In Restful Web services Client can directly access resource using URI which is an advantage of Restful Web services over SOAP Web services where the Client needs a WSDL file and stubs of SOAP Web services to access anything on the server.
  • The response message is self descriptive- it will contain the information of format in which the client can read the response message
  • Restful Web services uses concept of Uniform Interfaces- it uses HTTP
  • Stateless communication between Client and the server- every request is treated as a new request and should contain all information to establish the communication. As HTTP is a stateless communication protocol so Restful Web services uses it.
  • Restful Web services uses 4 main HTTP methods: GET – retrieve a resource, POST – create a resource, PUT – update a resource, DELETE – delete a resource. When we write a Restful Web services we implement all 4 methods for each resource in your Restful Web services program.
  • One of the widely used and accepted tool to test SOAP and RESTful Web services is SOAP UI
  • It’s a free and open source testing tool with an easy to use graphical interface.
  • In addition to functional testing there are many other features like security, load , test suit having n number of test cases and executing them all in one go with just one click and many other advanced features.
  • The latest version of the tool can be downloaded from http://wwwsoapui.org
  • Rest client-ui can be downloaded from https://code.google.com/p/rest-client/downloads/list
  • It is a very popular tool used to test Restful Web services.
  • Both the tools SOAP UI and Rest client-ui are easy to use.

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