Search your topic in Java2share
Home > FAQs
eXTReMe Tracker


Design Patterns FAQs


Untitled Document

Q29. How is JDO different from VO ?

JDO is a persistence technology that competes against entity beans in enterprise application development. It allows you to create POJOs (plain old java objects) and persist them to the database - letting JDO take care of the storage. Value objects, on the other hand, represent an abstract design pattern used in conjuction
with entity beans, jdbc, and possibly even JDO to overcome commonly found isolation and transactional problems in enterprise apps. Value objects alone do not allow you to persist objects - they are simple data holders used to transfer data from the database to the client and back to the database. Side note: I know that many books out there still refer to these data holders as value objects but the correct term is DTO: data transfer objects. Value objects refer to objects that hold a value. A good example of this java.lang.Integer object which holds an int.

Q30. How can I implement the MVC design pattern using JSP?

The MVC (Model View Controller) design pattern is a pattern/architecture that can be used by GUI's. It seperates the application's data, user interface and control logic into three separate entities. This ensures the system will be more maintainable in the future as changes to one component will not have an affect on the others.
The MVC pattern also conforms with the JSP Model 2 architecture.
The MVC pattern can be easily implemented in web applications using JSTL core, JSP,

Servlets and JavaBeans. JSTL makes it easy for HTML designers to use dynamic data in their pages without having to learn in depth java. The tags are in a recognizable HTML like format meaning a smaller learning curve than taking on the JSP specification after taking on the Java specification. JSTL also makes it easy for web developers who are developing all aspects of the application in helping you keep the content separate from the display by keeping your JSP clean from any Java code.