Java Reference
In-Depth Information
A complete lesson on designing Java
EE
applications is well beyond the scope of
this topic, but we'll walk you through some of the variations and exciting new possibil-
ities that come with enterprise
OSG
i.
5.3.1
Use small WABs
Many Java
EE
WAR
s are pretty big beasts. Not only does the
WAR
include its own code
and image resources, it often packages all of its dependencies in the
WEB-INF
/lib
folder. The
WAR
is acting almost like a mini-
EAR
, only with less explicit metadata.
Nobody likes massive
WAR
s, but sometimes keeping all your
JAR
s inside the lib direc-
tory is such an ingrained habit that you do it automatically. Remember—unlike
WAR
s,
WAB
s can be small, compact, and modular—and they're better that way (see figure 5.9).
small.wab
depA.jar
big.war
WEB-INF/
lib/
depA.jar
WEB-INF/
lib/
depB.jar
WEB-INF/
lib/
depC.jar
depB.jar
depC.jar
Figure 5.9
Whereas a WAR often needs to package all its code and dependencies inside the WAR
itself, WABs can be much more modular.
5.3.2
Make a persistence bundle
If your application is using persistence, it's a good idea to use a purpose-built persis-
tence bundle for the persistence.xml and the entity classes. This may be a bit different
from how you structured your persistence code for Java
EE
, but there's a good reason
for grouping everything together (see figure 5.10).
businesslogic.jar
Entity.class
BusinessLogic.class
BusinessLogic.class
persistencelogic.jar
AbstractEntity.class
Entity.class
persistence.xml
AbstractEntity.class
persistence.xml
Poor bundle organization
Good bundle organization
Figure 5.10
In an enterprise OSGi environment, it's important to package persistence
classes in the same bundle in which the persistence units are defined.
