Web services have the following characteristics:
(a) XML-based: A web service’s information representation and record transport layers employ XML. There is no need for networking, operating system, or platform bindings when using XML. At the mid-level, web offering-based applications are highly interactive.
(b) Loosely Coupled: The subscriber of an Internet service provider may not necessarily be directly connected to that service provider. The user interface for a web service provider may change over time without affecting the user’s ability to interact with the service provider. A strongly coupled system means that the decisions of the mentor and the server are inextricably linked, indicating that if one interface changes, the other must be updated.
A loosely connected architecture makes software systems more manageable and easier to integrate between different structures.
(c) Ability to be synchronous or asynchronous: Synchronicity refers to the client’s connection to the execution of the function. Asynchronous operations allow the client to initiate a task and continue with other tasks. The client is blocked, and the client must wait for the service to complete its operation before continuing in synchronous invocation.
Asynchronous clients get their results later, but synchronous clients get their effect immediately when the service is complete. The ability to enable loosely connected systems requires asynchronous capabilities.
(d) Coarse Grain: Object-oriented systems, such as Java, make their services available differently. At the corporate level, an operation is too great for a character technique to be useful. Building a Java application from the ground up requires the development of several granular strategies, which are then combined into a coarse grain provider that is consumed by the buyer or service.
Corporations should be coarse-grained, as should the interfaces they expose. Building web services is an easy way to define coarse-grained services that have access to substantial business enterprise logic.
(e) Supports remote procedural calls: Consumers can use XML-based protocols to call procedures, functions, and methods on remote objects that use web services. A web service must support the input and output framework of the remote system.
Enterprise-wide component development Over the years, JavaBeans (EJBs) and .NET components have become more prevalent in architectural and enterprise deployments. Several RPC techniques are used to both allocate and access them.
A web function can support RPC by providing its services, similar to a traditional role, or translating incoming invocations into an EJB or .NET component invocation.
(f) Supports document exchanges: One of the most attractive features of XML for communicating with data and complex entities.
Different Types of Web Services
Web services are mainly of two types. These are:
- SOAP Web Services
- 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:
- SOAP document has a root element termed as the <Envelope> element. This element is the initial element used in an XML document.
- 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.
- 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.