What are Web Services?

Web services overview-

A Web service, in very broad terms, is a method of communication between two applications or electronic devices over the World Wide Web (WWW). Web services are of two kinds: Simple Object Access Protocol (SOAP) and Representational State Transfer (REST).

SOAP and REST are two API styles that approach the question of data transmission from a different point of view. SOAP is a standardized protocol that sends messages using other protocols such as HTTP and SMTP. The SOAP specifications are official web standards, maintained and developed by the World Wide Web Consortium (W3C). As opposed to SOAP, REST is not a protocol but an architectural style. The REST architecture lays down a set of guidelines you need to follow if you want to provide a RESTful web service, for example, stateless existence and the use of HTTP status codes.

SOAP is an official protocol, it comes with strict rules and advanced security features such as built-in ACID compliance and authorization. Higher complexity, it requires more bandwidth and resources which can lead to slower page load times. REST was created to address the problems of SOAP. Therefore it has a more flexible architecture. It consists of only loose guidelines and lets developers implement the recommendations in their own way. It allows different messaging formats, such as HTML, JSON, XML, and plain text, while SOAP only allows XML. REST is also a more lightweight architecture, so RESTful web services have a better performance.

What does REST stand for?

REST stands for Representational State Transfer. It’s an architectural style that defines a set of recommendations for designing loosely coupled applications that use the HTTP protocol for data transmission. REST doesn’t prescribe how to implement the principles at a lower level. Instead, the REST guidelines allow developers to implement the details according to their own needs. Web services built following the REST architectural style are called RESTful web services. While accessing RESTful resources with HTTP protocol, the URL of the resource serves as the resource identifier and GET, PUT, DELETE, POST and HEAD are the standard HTTP operations to be performed on that resource.

To create a REST API, you need to follow six architectural constraints:-

  • Uniform interface – Requests from different clients should look the same, for example, the same resource shouldn’t have more than one URI.
  • Client-server separation – The client and the server should act independently. They should interact with each other only through requests and responses.
  • Statelessness – There shouldn’t be any server-side sessions. Each request should contain all the information the server needs to know.
  • Cacheable resources – Server responses should contain information about whether the data they send is cacheable or not. Cacheable resources should arrive with a version number so that the client can avoid requesting the same data more than once.
  • Layered system – There might be several layers of servers between the client and the server that returns the response. This shouldn’t affect either the request or the response.
  • Code on demand [optional] – When it’s necessary, the response can contain executable code (e.g., JavaScript within an HTML response) that the client can execute.

What does SOAP stand for?

SOAP stands for Simple Object Access Protocol. It’s a messaging protocol for interchanging data in a decentralized and distributed environment. SOAP can work with any application layer protocol, such as HTTP, SMTP, TCP, or UDP. It returns data to the receiver in XML format. Security, authorization, and error-handling are built into the protocol and, unlike REST, it doesn’t assume direct point-to-point communication. Therefore it performs well in a distributed enterprise environment.The Web Services Description Language (WSDL) describes a common set of rules to define the messages, bindings, operations and location of the service. WSDL is akin to a contract to define the interface that the service offers.

SOAP follows a formal and standardized approach that specifies how to encode XML files returned by the API. A SOAP message is, in fact, an ordinary XML file that consists of the following parts:-

Envelope (required) – This is the starting and ending tags of the message.

Header (optional) – It contains the optional attributes of the message. It allows you to extend a SOAP message in a modular and decentralized way.

Body (required) – It contains the XML data that the server transmits to the receiver.

Fault (optional) – It carries information about errors occurring during processing the message. Example -

<?xml version='1.0' Encoding='UTF-8' ?>
<env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope">
<m:reservation xmlns:m="http://travelcompany.example.org/reservation"
<n:passenger xmlns:n="http://mycompany.example.com/employees"
<n:name>Fred Bloggs</n:name>
<p:itinerary xmlns:p="http://travelcompany.example.org/reservation/travel">
<p:departing>New York</p:departing>
<p:arriving>Los Angeles</p:arriving>
<p:departureTime>late afternoon</p:departureTime>
<p:departing>Los Angeles</p:departing>
<p:arriving>New York</p:arriving>

Difference between SOAP AND RESTFUL API:-

  • REST API has no has no official standard at all because it is an architectural style. SOAP API, on the other hand, has an official standard because it is a protocol.
  • REST APIs uses multiple standards like HTTP, JSON, URL, and XML while SOAP APIs is largely based on HTTP and XML.
  • As REST API deploys multiple standards, so it takes fewer resources and bandwidth as compared to SOAP that uses XML for the creation of Payload and results in the large sized file.
  • The ways both APIs exposes the business logics are also different. REST API takes advantage of URL exposure like @path("/WeatherService") while SOAP API use of services interfaces like @WebService.
  • SOAP API defines too many standards, and its implementer implements the things in a standard way only. In the case of miscommunication from service, the result will be the error. REST API, on the other hand, don't make emphasis on too many standards and results in corrupt API in the end.
  • REST API uses Web Application Description Language, and SOAP API used Web Services Description language for describing the functionalities being offered by web services.
  • REST APIs are more convenient with JavaScript and can be implemented easily as well. SOAP APIs are also convenient with JavaScript but don't support for greater implementation.

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