J2EE 1 Agenda Application servers What is J2EE 1 2 3 4 Main component types Application Scenarios J2EE APIs and Services EJB a closer look Examples 2 1 Application Servers In the beginning there was darkness and cold Then mainframe terminals terminals Centralized non distributed 3 Application Servers In the 90 s systems should be clientserver 4 Application Servers Today enterprise applications use the multi tier model 5 Application Servers Multi tier applications have several independent components An application server provides the infrastructure and services to run such applications 6 Application Servers Application server products can be separated into 3 categories J2EE based solutions Non J2EE solutions PHP ColdFusion Perl etc And the Microsoft solution ASP COM and now NET with ASP NET VB NET C etc 7 J2EE Application Servers Major J2EE products BEA WebLogic IBM WebSphere Sun iPlanet Application Server Oracle 9iAS HP Bluestone Total e Server Borland AppServer Jboss free open source 8 Web Server and Application Server App Server 1 Internet Browser Web Server HTTP Server HTTP S App Server 2 9 2 What is J2EE It is a public specification that embodies several technologies Current version is 1 6 J2EE defines a model for developing multi tier web based enterprise applications with distributed components 10 J2EE Benefits High availability Scalability Integration with existing systems Freedom to choose vendors of application servers tools components Multi platform 11 J2EE Benefits Flexibility of scenarios and support to several types of clients Programming productivity Services allow developer to focus on business Component development facilitates maintenance and reuse Enables deploy time behaviors Supports division of labor 12 Main technologies JavaServer Pages JSP Servlet Enterprise JavaBeans EJB JSPs servlets and EJBs are application components 13 JSP Used for web pages with dynamic content Processes HTTP requests non blocking call and return Accepts HTML tags special JSP tags and scriptlets of Java code Separates static content from presentation logic Can be created by web designer using HTML tools 14 Servlet Used for web pages with dynamic content Processes HTTP requests non blocking calland return Written in Java uses print statements to render HTML Loaded into memory once and then called many times Provides APIs for session management 15 EJB EJBs are distributed components used to implement business logic no UI Developer concentrates on business logic Availability scalability security interoperability and integrability handled by the J2EE server Client of EJBs can be JSPs servlets other EJBs and external aplications Clients see interfaces 16 J2EE Multi tier Model 17 J2EE Application Scenarios Multi tier typical application 18 J2EE Application Scenarios Stand alone client 19 J2EE Application Scenarios Web centric application 20 J2EE Application Scenarios Business to business 21 J2EE Services and APIs Java Message Service JMS Implicit invocation Communication is loosely coupled reliable and asynchronous Supports 2 models point to point publish subscribe 22 JMS Point to point Destination is queue 23 JMS Publish subscribe Destination is topic 24 J2EE Services and APIs JNDI Naming and directory services Applications use JNDI to locate objects such as environment entries EJBs datasources message queues JNDI is implementation independent Underlying implementation varies LDAP DNS DBMS etc 25 J2EE Services and APIs Transaction service Controls transactions automatically You can demarcate transactions explicitly Or you can specify relationships between methods that make up a single transaction 26 J2EE Services and APIs Security Java Authentication and Authorization Service JAAS is the standard for J2EE security Authentication via userid password or digital certificates Role based authorization limits access of users to resources URLs EJB methods Embedded security realm 27 J2EE Services and APIs J2EE Connector Architecture Integration to non J2EE systems such as mainframes and ERPs Standard API to access different EIS Vendors implement EIS specific resource adapters Support to Corba clients 28 J2EE Services and APIs JDBC JavaMail Java API for XML Parsing JAXP Web services APIs 29 3 EJB a closer look 30 Home Interface Methods to create remove or locate EJB objects The home interface implementation is the home object generated The home object is a factory 31 Remote Interface Business methods available to clients The remote interface implementation is the EJB object generated The EJB object acts as a proxy to the EJB instance 32 EJB The Big Picture 33 EJB at runtime Client can be local or remote 34 EJB at runtime 35 Types of EJB EJB Taxonom y E n te rp rise B e a n Se ssio n B e a n E n tity B e a n Sta te fu l BM P Sta te le ss CMP M e ssa g e D riv e n B e a n New 36 Session Bean Stateful session bean Retains conversational state data on behalf of an individual client If state changed during this invocation the same state will be available upon the following invocation Example shopping cart 37 Session Bean Stateless session bean Contains no user specific data Business process that provides a generic service Container can pool stateless beans Example shopping catalog 38 Entity Bean Represents business data stored in a database persistent object Underlying data is normally one row of a table A primary key uniquely identifies each bean instance Allows shared access from multiple clients Can live past the duration of client s session Example shopping order 39 Entity Bean Bean managed persistence BMP bean developer writes JDBC code to access the database allows better control for the developer Container managed persistence CMP container generates all JDBC code to access the database developer has less code to write but also less control 40 Message Driven Bean Message consumer for a JMS queue or topic Benefits from EJB container services that are not available to standard JMS consumers Has no home or remote interface Example order processing stock info 41 4 Examples JSP example Servlet example EJB example 42 JSP example 43 JSP example page import hello Greeting jsp useBean id mybean scope page class hello Greeting jsp setProperty name mybean property html head title Hello User title head body bgcolor ffffff background background gif include file dukebanner html table border 0 width 700 tr td width 150 nbsp td td width 550 h1 My name is Duke What s yours h1 td tr 44 JSP example tr td width 150