Overview of Enterprise JavaBeans (EJB)


  Enterprise JavaBeans.ppt (Size: 186.5 KB / Downloads: 0)

Applications to Date

Web Applications (Servlets/JSPs)
Provided user interface
access to database
simple business logic
no transactions except at the database level; no distributed transactions across business logic
Distributed Applications (RMI)
Distributed access to business logic
access to, but no direct support for database
limited transactions
We have to write a lot of ‘plumbing’ code

What didn’t we address ?

Could someone else deploy your application?
Component reusability
Security
Threading
Resource Management
Load-Balancing
Fault Tolerance (a little with activation)

Component Transaction Monitors (CTMs)

Sophisticated distributed object Application Servers
usually made up of web servers, ORBs, Messaging, Databases, Naming, etc.
Hybrid of TP Monitors (e.g., CICS and Tuxedo)and ORBs (e.g., CORBA and RMI)
Provide infrastructure for managing transactions, object distribution, concurrency, security, persistence, and resource management
the developer isn’t left “rolling their own”
the developer complies with the model and basically implements a lot of callback event and declarative programming
Analogy: CD-player = CTM, CD = Server-side Component

Enterprise JavaBeans (EJBs)

Standard server-side component model for Java Enterprise Applications
security
resource pooling
persistence
concurrency
transactional integrity
Has nothing to do with “JavaBeans”
JavaBeans designed for intra-process purposes
GUIs
non-visual widgets
Enterprise Java Beans (EJB) designed for inter-process purposes