Lao Li share: What is WebService?

Objective

Web Services are open standards (XML, SOAP, HTTP, and so on) that Web applications are designed to interact with for other Web applications.
Web Services can convert your existing applications into Web applications.
In this series of guides, you will learn what Web Services are, why, and how to use them. This series of guides will be useful to those who are interested in learning the basics of Web Services and implementing them in practice.
This is a basic tutorial on the concept of Web Services and does not require the reader to have prior knowledge of these technologies, but it is certainly easier to read if you have a basic understanding of the concepts of XML, HTTP, TCP/IP, and so on.

Defined

Many different books, or different organizations, provide different definitions for Web Services. Some of these definitions are listed below.

• A Web service is any software that enables itself to be accessed over the Internet and using a standardized XML messaging system. XML is used to encode all communications to and from the Web service. For example, a client invokes a Web service by sending an XML message, and then waits for a corresponding XML response. Because all communications are XML-based, Web service is not bound to a specific operating system or programming language--java can interact with Perl, and Windows applications can interact with Unix applications.
• Web Service is a standalone, modular, distributed, dynamic application that can be described, published, positioned, or created through a network to create products, processes, and supply chains. These applications can be localized, distributed, or Web-based. Web Service is built on open standards such as TCP/IP, HTTP, Java, HTML, and XML.
• Web Service is an XML-based information Exchange system that uses the Internet for direct application-to-application interaction. Such a system can contain programs, objects, messages, or documents.
• A Web service is a collection of open protocols and standards that are used to exchange data between applications or systems. Software applications that are written in different languages and run on different platforms can use Web service to interact with data over a computer network, just like interprocess communication on a single computer. This interoperability (for example, between Java and Python, or between Windows and Linux applications) is attributed to the use of open standards.

As a summary, a complete Web service is any service that meets the following criteria:

• Access via Internet or private (intranet) network
• Use a standardized XML messaging system
• Not tied to any operating system or programming language
• The self-descriptive nature of a common XML syntax
• Accessibility through a simple discovery mechanism

Web Service Components

The basic Web service platform is XML + HTTP. All standard Web service uses the following components:

• SOAP (Simple Object Access Protocol)
• UDDI (general description, Discovery, and integration)
• WSDL (Web Service Description Language)

All of these components will be discussed in the Web Service section.

a Web Service How does it work?

A Web service guarantees communication between different applications by using open standards such as HTML, XML, WSDL, and SOAP. A Web service requires these elements:

• XML Tag Data
• SOAP Transport Messages
• WSDL to describe the availability of the service

You can build a Java-based Web service on Solaris that can be accessed by a VB program that you run on Windows.
You can also use C # to build a new Web service on Windows that can be called by your JSP-based Web application that runs on Linux.

Example

Suppose there is a simple account management and order Processing system. Accountants use a client application built in VB or JSP to create new accounts and enter new customer orders.
The system's processing logic is written in Java and placed on a Solaris host, which also interacts with a db to hold the data.
Here are the steps to perform this action:

1. The client program encapsulates the account registration information into a SOAP message
2. This SOAP message is sent as an HTTP POST request body to the Web service
3. The Web service will unpack the SOAP request and translate it into an instruction that the application can understand
4. The app processes the required information and responds with a new unique account for that user
5. Next, the Web service packages the response to another SOAP message and returns it to the client application as a response to the HTTP request
6. The client applies the unpacking SOAP message to obtain the processing result of the account registration

Lao Li share: What is WebService?