Web Based Services, Lecture Notes - Computer Science - 13, Study notes of Computers and Information technologies

Download Web Based Services, Lecture Notes - Computer Science - 13 and more Study notes Computers and Information technologies in PDF only on Docsity!

Web Based Commerce 514H

Dr Kingsley Sage Room 2R308, Chichester II khs20@sussex.ac.uk © University of Sussex 2009

Lecture 9

 Revision  What have we learned?

Layered systems

 Complex enterprise information systems are built in layers:

• So that we can manage their development
• With different people working in their specialisms with the right tools
• So that we can understand and isolate the interactions between the different layers

A layered information system

 These layers may sometimes exist only as design abstractions

• may be tangled implementations  In many cases these layers are clearly identifiable and may be isolated sub-systems operating on disparate platforms

MVC-

 JSP Model 2 (or MVC-2) is Sun’s attempt to wrap their Java Server Pages (JSP) within the MVC paradigm  A set of guidelines that go along with Sun’s packaging of Java under J2EE  JSP is responsible for generating the view  Also specifies the Java Standard Tag Library (JSTL)

Apache Struts - overview

 Apache Struts is a free, open-source framework for creating Java web applications and was developed by the Apache Software Foundation  Struts is highly configurable and has a large and growing feature list including:

• Controller
• Action classes and mappings
• Utility classes for XML (useful with web services)
• Web forms with validation  Also includes custom tag libraries for things like:
• Accessing server side state
• Creating HTML, performing presentation logic

Back End Systems

MySQL (or another RDBMS) Persistence Layer Connection Management Connector/J Resource management layer

JDBC

 Java Data Base Connector (JDBC) is a call-level Application Programming Interface that allows Java to communicate with SQL databases  You also need the Connector/J driver  JDBC allows Java to execute commands and queries directly  Can write web applications that use JDBC directly (like you did in the lab session)  Or you can use EJBs and Persistence 1.0 layer to manage persistence, in which case use of JDBC is transparent

J2EE

J2EE (2)

 The J2EE embodies technologies to support multi-tier enterprise applications. These fall into 3 categories:

• component :
• service :
• communication :  run time support of a system level entity called a container:
• web container: such as embedded Apache Tomcat – used to provide servlet functions and to execute web clients such as those that call EJBs
• Enterprise Java Beans container: provides the infrastructure for all the EJB bean types

J2EE component types and their

containers

Enterprise Java Beans components

 A server side technology for developing and deploying components containing the business logic of an enterprise application  EJB components are:

• scalable
• transactional
• multi-user secure  Three types of bean:
• Entity beans
• Session beans
• Message driven beans

Web services

 Although web services means lots of things to different communities, J2EE takes a fairly narrow view  A web service is a remote application described using the Web Service Description Language (WSDL) and accessed using the Simple Object Application Protocol (SOAP) according to the rules defined by the WS-I Basic Profile 1.

Web services (2)

 Simple Object Application Protocol (SOAP)  Web Services Description Language (WSDL)  Universal Description, Discovery and Integration (UDDI) is a specification that describes a standard for publishing and discovering web services on the Internet

And finally …

 Assignment 2 due week 2 in Summer Term  Anirban and Kingsley available to answer questions for assignment 2 by e-mail over the Easter break  Group progress meeting in week 9 (all group members expected to attend)