Web Services and Development Khanewal

What Are Web Services? Easy-to-Learn Concepts with Examples

You can’t mention the term “web services” nowadays without immediately evoking references to Amazon Web Services or Google’s Web service, Google Cloud Platform. There’s a reason for that, though. These tech giants have raised the bar by addressing the need for application development. And scale from the likes of Amazon and Google is exactly what makes modern web services possible.

However, despite all of its technological advancements, web service testing and processes are still complex animals. Since they depend on operating systems to manage applications, the smallest of variances can result in multifaceted workflows when trying to move data between servers and the cloud, which can throw a wrench into your ecosystem and application integration strategy.

But with APIs, web developers can integrate advanced functions and features into apps, allowing for much better customization and flexibility. And the end result is a better experience for users and customers. They reap the benefits of well-built web APIs, increasing efficiency and practicality of services and apps. At the end of the day, the goal is to offer an enjoyable experience.

What are Web Services

There is more than one way to answer, “What is a web service?” But, essentially, web services include any software, application, or cloud technology that provides standardized web protocols (HTTP or HTTPS) to interoperate, communicate, and exchange data messaging – usually XML (Extensible Markup Language) – throughout the internet.

In other words, web services are XML-centred data exchange systems that use the internet for A2A (application-to-application) communication and interfacing. These processes involve programs, messages, documents, and/or objects.

A key feature of web services is that applications can be written in various languages and are still able to communicate by exchanging data with one another via a web service between clients and servers. A client summons a web service by sending a request via XML, and the service then responses with an XML response. Web services are also often associated with SOA (Service-Oriented Architecture).

To break that down, a web service comprises these essential functions:

• Available over the internet or intranet networks
• Standardised XML messaging system
• Independent of a single operating system or programming language
• Self-describing via standard XML language
• Discover able through a simple location method

A web service supports communication among numerous apps with HTML, XML, WSDL, SOAP, and other open standards. XML tags the data, SOAP transfers the message, and WSDL describes the service’s accessibility.

Here’s an instance of how it works: A web service sits between two sets of java, .net, or PHP apps providing a way for these applications to communicate over a network. On one side, for example, a java app interacts with the java, .net, and PHP apps on the other end by way of the web service communicating an independent language.

Web services offer different benefits across business operations. The technology helps IT pros and web architects streamline connectivity by minimizing development time. And with this simplified infrastructure, company executives begin to see higher ROI (return on investment). In a B2B operation where both parties understand how the process works, web services provide efficient technology distribution throughout an entire network.

What are the Different Types of Web Services

There are a few central types of web services: XML-RPC, UDDI, SOAP, and REST:

XML-RPC (Remote Procedure Call) is the most basic XML protocol to exchange data between a wide variety of devices on a network. It uses HTTP to quickly and easily transfer data and communication other information from client to server.

UDDI (Universal Description, Discovery, and Integration) is an XML-based standard for detailing, publishing, and discovering web services. It’s basically an internet registry for businesses around the world. The goal is to streamline digital transactions and e-commerce among company systems.

SOAP, which will be described in detail later in the blog, is an XML-based Web service protocol to exchange data and documents over HTTP or SMTP (Simple Mail Transfer Protocol). It allows independent processes operating on disparate systems to communicate using XML.

REST, which will also be described in great detail later in the blog, provides communication and connectivity between devices and the internet for API-based tasks. Most Restful services use HTTP as the supporting protocol.

What is Web Service

Web service is a standardized medium to propagate communication between the client and server applications on the WWW (World Wide Web). A web service is a software module that is designed to perform a certain set of tasks.

• Web services in cloud computing can be searched for over the network and can also be invoked accordingly.
• When invoked, the web service would be able to provide the functionality to the client, which invokes that web service.

• The above diagram shows a very simplistic view of how a web service would actually work. The client would invoke a series of web service calls via requests to a server which would host the actual web service.

  These requests are made through what is known as remote procedure calls. Remote Procedure Calls(RPC) are calls made to methods which are hosted by the relevant web service.

• As an example, Amazon provides a web service that provides prices for products sold online via amazon.com. The front end or presentation layer can be in .Net or Java but either programming language would have the ability to communicate with the web service.

  The main component of a web service design is the data which is transferred between the client and the server, and that is XML. XML (Extensible markup language) is a counterpart to HTML and easy to understand the intermediate language that is understood by many programming languages.

  So when applications talk to each other, they actually talk in XML. This provides a common platform for application developed in various programming languages to talk to each other.

  Web services use something known as SOAP (Simple Object Access Protocol) for sending the XML data between applications. The data is sent over normal HTTP. The data which is sent from the web service to the application is called a SOAP message. The SOAP message is nothing but an XML document. Since the document is written in XML, the client application calling the web service can be written in any programming language.

Why do you need a Web Service

• Modern day business applications use variety of programming platforms to develop web-based applications. Some applications may be developed in Java, others in .Net, while some other in Angular JS, Nodes, etc.

  Most often than not, these heterogeneous applications need some sort of communication to happen between them. Since they are built using different development languages, it becomes really difficult to ensure accurate communication between applications.

  Here is where web services come in. Web services provide a common platform that allows multiple applications built on various programming languages to have the ability to communicate with each other.

Type of Web Service

• There are mainly two types of web services.

  1. SOAP web services.
  2. Restful web services.

  In order for a web service to be fully functional, there are certain components that need to be in place. These components need to be present irrespective of whatever development language is used for programming the web service.

  Let’s look at these components in more detail. 

  SOAP is known as a transport-independent messaging protocol. SOAP is based on transferring XML data as SOAP Messages. 

  Here is what a SOAP message consists of

  • Each SOAP document needs to have a root element known as the <Envelope> element. The root element is the first element in an XML document.
  • The “envelope” is in turn divided into 2 parts. The first is the header, and the next is the body.
  • The header contains the routing data which is basically the information which tells the XML document to which client it needs to be sent to.
  • The body will contain the actual message.Each message has something which is known as an XML document. Only the structure of the XML document follows a specific pattern, but not the content. The best part of Web services and SOAP is that its all sent via HTTP, which is the standard web protocol.

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Web Services Advantages

• We already understand why web services came about in the first place, which was to provide a platform which could allow different applications to talk to each other.

  But let’s look at the list of web services advantages for why it is important to use web services.

1. Exposing Business Functionality on the network – A web service is a unit of managed code that provides some sort of functionality to client applications or end users. This functionality can be invoked over the HTTP protocol which means that it can also be invoked over the internet. Nowadays all applications are on the internet which makes the purpose of Web services more useful. That means the web service can be anywhere on the internet and provide the necessary functionality as required.
2. Interoperability amongst applications – Web services allow various applications to talk to each other and share data and services among themselves. All types of applications can talk to each other. So instead of writing specific code which can only be understood by specific applications, you can now write generic code that can be understood by all applications
3. A Standardized Protocol which everybody understands – Web services use standardized industry protocol for the communication. All the four layers (Service Transport, XML Messaging, Service Description, and Service Discovery layers) uses well-defined protocols in the web services protocol stack.
4. Reduction in cost of communication – Web services use SOAP over HTTP protocol, so you can use your existing low-cost internet for implementing web services.

Web Services Architecture

• • Every framework needs some sort of architecture to make sure the entire framework works as desired, similarly, in web services. The Web Services Architecture consists of three distinct roles as given below :

    1. Provider – The provider creates the web service and makes it available to client application who want to use it.
    2. Requester – A requester is nothing but the client application that needs to contact a web service. The client application can be a .Net, Java, or any other language based application which looks for some sort of functionality via a web service.
    3. Broker – The broker is nothing but the application which provides access to the UDDI. The UDDI, as discussed in the earlier topic enables the client application to locate the web service.

    The diagram below showcases how the Service provider, the Service requestor and Service registry interact with each other.

    
    

    Web Services Architecture

    1. Publish – A provider informs the broker (service registry) about the existence of the web service by using the broker’s publish interface to make the service accessible to clients
    2. Find – The requestor consults the broker to locate a published web service
    3. Bind – With the information it gained from the broker(service registry) about the web service, the requestor is able to bind, or invoke, the web service.

Web service Characteristics

• • Web services have the following special behaviour characteristics:

    1. They are XML-Based – Web Services uses XML to represent the data at the representation and data transportation layers. Using XML eliminates any networking, operating system, or platform sort of dependency since XML is the common language understood by all.
    2. Loosely Coupled – Loosely coupled means that the client and the web service are not bound to each other, which means that even if the web service changes over time, it should not change the way the client calls the web service. Adopting a loosely coupled architecture tends to make software systems more manageable and allows simpler integration between different systems.
    3. Synchronous or Asynchronous functionality – Synchronicity refers to the binding of the client to the execution of the service. In synchronous operations, the client will actually wait for the web service to complete an operation. An example of this is probably a scenario wherein a database read and write operation are being performed. If data is read from one database and subsequently written to another, then the operations have to be done in a sequential manner. Asynchronous operations allow a client to invoke a service and then execute other functions in parallel. This is one of the common and probably the most preferred techniques for ensuring that other services are not stopped when a particular operation is being carried out.
    4. Ability to support Remote Procedure Calls (RPCs) – Web services enable clients to invoke procedures, functions, and methods on remote objects using an XML-based protocol. Remote procedures expose input and output parameters that a web service must support.
    5. Supports Document Exchange – One of the key benefits of XML is its generic way of representing not only data but also complex documents. These documents can be as simple as representing a current address, or they can be as complex as representing an entire book.