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J2EE Design Patterns —
Business Tier
Pattern Samples
These business tier patterns tackle problems occuring in
an application resulting from the presentation tier accessesing distributed
business services, network performances degradation due to multiple
calls between client and server, memory impact due to retrieval
of a large list of data, and so on. The patterns demonstrated here focus on
and solve design problems occuring in the middle tier of a J2EE
application.
Session Facade Design Pattern [14-Dec-2004]
In a J2EE application clients need access to
business objects represented by EJBs to fulfill their responsibilities
and to meet user requirements. If EJB clients access entity beans
directly over the network, they must make numerous remote calls leading
to increased network traffic and reduced performance . A session facade
solves such problems by presenting client objects with a unified interface
to the underlying EJBs. Client objects interact only with the facade
( a Stateless Session Bean), which resides on the server and invokes
the appropriate EJB methods.
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Now (ZIP, 88KB)
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Service Locator Design Pattern [05-Nov-2004]
J2EE uses the JNDI tree to lookup, access and
invoke business services on passing a unique registered JNDI name.
If the service is used by various clients, then the code for looking
up the object gets duplicated in various forms which makes it difficult
to maintain the application. This pattern is used to address this
issue by storing the lookup values for all services in a single place
and provide it on request.
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Now (ZIP, 197KB)
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Value List Handler Pattern [12-Aug-2004]
The Value List Handler pattern provides an
efficient way to retrieve large amounts of data from data
sources. Typically, when an application retrieves a large list
of data, transmitting the whole list to a client results in poor
performance due to latency of response and need for a large memory
footprint. Using the scenario of Order Entry, this sample application
demonstrates the effective use of the value list handler pattern.
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Now (ZIP, 124KB)
Readme
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