Web services have become an essential element of development for web developers. These types of applications are standard ways of interconnecting and operating contrasting web applications. It helps other web applications and apps to run smoothly just by plugging its utilities on to your web applications. In this chapter, you will learn about the different types of web services and their usage.

What are Web Services?

A Web service is a software package that is used for communicating between two devices or web entities lying on the network. They involve a service provider along with a service requester, i.e., the client. Since Web services are advantageous as they are language transparent, so there is no issue whether the fundamental system is providing the service developed in Java, PHP, or any other language. At the same time, the client application is written in Python, Ruby, Perl, or JavaScript.

Web services perform specific tasks. These are:

  • Usually, web services are searched for over the network as well as call upon accordingly.
  • As a web service is called, it would be capable of providing operation for the client that has invoked the web service.

Different Types of Web Services

Web services are mainly of two types. These are:
  1. SOAP Web Services
  2. REST Web Services

The SOAP Web Services

It is an XML-based protocol having the main benefit of implementing the SOAP Web Service as its security. The abbreviation of SOAP is the Simple Object Access Protocol. SOAP offers a wrapper for sending web service-based messages over the Internet with the help of HTTP protocol. All its messages are usually in XML format. The SOAP message consists of:

  1. SOAP document has a root element termed as the <Envelope> element. This element is the initial element used in an XML document.
  2. Then next to the "envelope," which is categorized into two parts. The former is the 'header,' and the later is the 'body.' The header includes the routing-data that is essentially the information telling the XML document to whom or for which the client needs to be sent.
  3. Lastly, the body includes the actual message.

The REST (Representational State Transfer) Web services

REST service is not a collection of a paradigm or specific rules; it is instead the style architecture for software. Those apps that are designed using this architecture are collectively termed as RESTful web services. Contrasting SOAP, which aims at actions, REST deals majorly on the resources.

It establishes the resources through the use of URL as well as depends on the nature of the transport protocol (like HTTP's: GET, PUT, POST, DELETE, etc.) used to perform the resources. The allocation of resources in REST depends on the URL. It is more like conventions based application.

Web Service Architecture

Each of the web frameworks needs some architecture for making the entire framework works as required. There are three discrete roles as mentioned below regarding the web services:

  • The provider: is used to create web service, which makes it accessible for client applications who want to utilize it.
  • The requestor: is not anything but the client app which requires contacting a web service. That client app can be ".Net", "Java", or any other language-based application that seeks functionality through a web service.
  • The broker or service registry: is the application that helps in providing access to the UDDI (Universal Description, Discovery, and Integration), which is a paradigm to describe, publish as well as discover web services that are provided by any particular service provider.

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