Introduction to Web Services PDF

Introduction to Web Services Mr. DAVID ERIC S. ORETA Instructor I College of Computing and Multimedia Studies Enverga University Web Service Web service is a standardized medium to propagate communication between the client and server applications on the World Wide Web. Web services provid...

Introduction to Web Services Mr. DAVID ERIC S. ORETA Instructor I College of Computing and Multimedia Studies Enverga University Web Service Web service is a standardized medium to propagate communication between the client and server applications on the World Wide Web. Web services provide a common platform that allows multiple applications built on various programming languages to have the ability to communicate with each other. Web Service A web service is a software module which is designed to perform a certain set of tasks. The web services can be searched for over the network and can also be invoked accordingly. When invoked the web service would be able to provide functionality to the client which invokes that web service. Web Service A complete web service is, any service that: Is available over the Internet or private (intranet) networks Uses a standardized XML messaging system Is not tied to any one operating system or programming language Is self-describing via a common XML grammar Is discoverable via a simple find mechanism Agoda.com Web Service Architecture Diagram Web Service Architecture Diagram (cont’d) The requests made by a client is known as remote procedure calls. Remote Procedure Calls(RPC) are calls made to methods which are hosted by the relevant web service. The main component of a web service is the data which is transferred between the client and the server, and that is XML. 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 Service Architecture Diagram (cont’d) Web services use something known as SOAP (Simple Object Access Protocol) for sending the XML data between applications. 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. Popular Web Services Protocols XML:RPC XML-RPC is a simple protocol that uses XML messages to perform RPCs. Requests are encoded in XML and sent via HTTP POST. XML responses are embedded in the body of the HTTP response. XML-RPC is platform-independent. XML-RPC allows diverse applications to communicate. XML-RPC is the easiest way to get started with web services. Popular Web Services Protocols (cont’d) SOAP: SOAP is known as the Simple Object Access Protocol. SOAP was developed as an intermediate language so that applications built on various programming languages could talk quickly to each other and avoid the extreme development effort. Popular Web Services Protocols (cont’d) SOAP: Components Each SOAP document needs to have a root element known as the 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. Popular Web Services Protocols (cont’d) Popular Web Services Protocols (cont’d) Simple communication via SOAP Popular Web Services Protocols (cont’d) WSDL: WSDL is known as the Web Services Description Language(WSDL). WSDL is an XML-based file which tells the client application what the web service does and gives all the information required to connect to the web service. Popular Web Services Protocols (cont’d) How can a client application locate a WSDL file to understand the various operations offered by a web service? Universal Description, Discovery, and Integration (UDDI) UDDI is a standard for describing, publishing, and discovering the web services that are provided by a particular service provider. It provides a specification which helps in hosting the information on web services. The client application will have complete access to the UDDI, which acts as a database containing all the WSDL files. Popular Web Services Protocols (cont’d) Just as a telephone directory has the name, address and telephone number of a particular person, the same way the UDDI registry will have the relevant information for the web service. So that a client application knows, where it can be found. Popular Web Services Protocols (cont’d) REST: REST stands for REpresentational State Transfer. REST is used to build Web services that are lightweight, maintainable, and scalable. Web Services Advantages 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. Web Services Advantages (cont’d) 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. A Standardized Protocol which everybody understands Web services use standardized industry protocol for the communication. Web Services Advantages (cont’d) Reduction in cost of communication Web services use SOAP over HTTP protocol, so the use of existing low-cost internet for implementing web services. End of Presentation