J2SE/J2EE • J2SE – Java 2, Standard Edition • “core” java – the base classes on which everything else is built • Base tools and utilities • J2EE – Java 2, Enterprise Edition • APIs and technologies for delivering multi-tier “enterprise” applications • Web Applications • Web Services
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J2SE/J2EE J2SE – Java 2, Standard Edition “core” java – the base classes on which everything else is built Base tools and utilities J2EE – Java 2, Enterprise.
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J2SE/J2EE• J2SE – Java 2, Standard Edition
• “core” java – the base classes on which everything else is built
• Base tools and utilities• J2EE – Java 2, Enterprise Edition
• APIs and technologies for delivering multi-tier “enterprise” applications
• XML Processing• SQL Processing• Accessing java objects
• Standard way to build your own taglibs
J2EE - EJB• Enterprise Java Beans – EJB
• A “Component Based Architecture”• You can build business objects as components and the EJB
framework gives you:• Built-in transactional support
• Automatic commit/rollback• Security
• Access on a per-method basis• DB Access
• No need to write SQL• Distributed Objects
• Allows you to distribute parts of your application across VMs or different machines
• Distributed transactions all within one unit of work
J2EE - EJB• Probably use EJBs when:
• Business Reasons• Your system is truly transactional
• All changes need to happen or not at all
• High-volume updates• Multi-user access to the same objects
• Multi-user access to the same data rows in a DB
• Technical Reasons• Many many tables that must be updated• You want to provide a transaction as a service
• Available to other applications
J2EE - EJB• Probably don’t use EJBs (may be overkill) when:
• Application is “read-only”• Viewing account info on-line, no updates
• Application is not transactional in nature• Application is “single user”
• User alone has access to his data
J2EE - EJB• 2 Types of EJBs
• Entity Beans• Concrete business objects whose data is transaction
dependent• Used across transactions• Can be shared by multiple users• Rows in a database table• Examples
• Account• Payment• Charge
• Session Beans• Associated with a User Login• Controls a transaction where multiple Entity Beans participate• The main entry point for a business transaction
EJB example (database view) AccountNum Address123 55 Main St.987 33 Grand Ave.
AcctActivitynum type amount123 pur 12.00
PurchaseOrdernum qty item amount123 4 BB 8.00123 1 WI 4.00