W R I T E   A N D   D E P L O Y   J 2 E E   A P P L I C A T I O N S  

Chapter  

6 

6. Write and Deploy J2EE Applications 

How to write and deploy EJB and Web applications 

This chapter gives you an introduction on how to write J2EE applications for JBoss but does 

not discuss how to write EJBs, Servlets or JSPs etc. in general. There are some good books 

available explaining how to write EJBs and Web applications. Because the Template project 

from chapter 3 is used here the code snippets are mostly from XDoclet generated files and 

you will find these files in the  build  directory of the Template project. 

EJBs and Web components like Servlets, JSPs etc. are the heart of the server side J2EE 

application. They have all in common to reside in their container that is part of the J2EE 

application server. For convenience sake they can be deployed as Java archives with 

different extensions. These achieves contain a vendor neutral deployment descriptor (or DD 

for short), 0 to n vendor specific DDs, other archives if available, compiled Java classes, 

JSPs, HTML Pages and other resource files. In JBoss they can be hot deployed with a drop 

in the deployment archive and replaces any existing applications with the same name. 

Entity Beans 

Entity Beans represent unit of data that is in a relational database a record. It encapsulates 

the database specifics as well as the integration into transactions and the timing when the 

data is synchronized with the persistence store. 

As a rule of thumb Entity Beans should not contain any business logic but only data 

integrity and persistence logic. 

Bean Managed Persistence (BMP) 

Bean Managed Persistence means that the Bean Developer coded the logic how the data is 

made persistent on the target persistence store like a RDBMS. This also means that most 

likely the EJB is specific for a certain persistence store even thought the application is 

written vendor neutral. 

The code how to store or retrieve data from the persistence store are added to the ejbStore() 

and ejbLoad() methods. It is the client's responsibility to retrieve the correct resource 

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