Intro to Web Services Dr. John P. Abraham UTPA

What are Web Services? Applications execute across multiple computers on a network.  The machine on which web service resides is the REMOTE MACHINE.  When clients uses a web service the class and compile DLL are stored on the Remote Machine.  Remote machines superior computing power can be utilized as well.

Web services promotes software re-usability promotes collaboration Web service is a class  Whose methods can be called by methods running on other machines (see Simple Object Access Protocol in later slides).  Requests and responses are transmitted via SOAP

Web services The basic Web services platform is XML + HTTP Web services platform elements  SOAP (Simple Object Access Protocol)  UDDI (Universal Description, Discovery and Integration)  WSDL (Web Services Description Language)

SOAP Simple Object Access Protocol. SOAP is a communication protocol SOAP is for communication between applications SOAP is a format for sending messages SOAP is designed to communicate via Internet SOAP is platform and language independent (SOAP messages are written in XML) SOAP allows you to get around firewalls  Most firewalls do not restrict XML & HTTP traffic.

SOAP Interaction When a program invokes a method, the request and all relevant information (parameters) are packaged in a SOAP message and sent to the Remote machine. The Remote machine (server) parses the SOAP message for Method and parameters. Response is sent as a SOAP message.

UDDI Like the yellow pages of Web services Universal Description, Discovery and Integration UDDI is a directory for storing information about web services UDDI is a directory of web service interfaces described by WSDL UDDI communicates via SOAP UDDI is built into the Microsoft.NET platform

WSDL Web Services Description Language WSDL is written in XML WSDL is an XML document WSDL is used to describe Web services WSDL is also used to locate Web services

Creating Web Services Visual web developer and the.NET framework used to develop web services. Creating a web service is known as Publishing. Using a web service is known as Consuming. The Web service has two parts: A proxy class representing the web service and a client application that access the web service via an instance of the proxy class.

Creating a Web service Visual Basic 2005 and Visual Web developer can create the proxy classes for you. Several JAVA APIs facilitate web services.  Netbeans allows a programmer to publish and/or consume web services.  Requests and responses are created with JAX- WS, which are transmitted via SOAP