Bitter JSPs - Bitter Java - page 104

S YMPTOMS , CONSEQUENCES : View redesigns, no matter how small, ripple
into other places of the JSP and into other parts of the system. The code is
very difficult to read.
A LTERNATIVE SOLUTIONS : Many versions of command design patterns
exist, dating back to early Smalltalk programming. These are some popu-
lar alternatives:
The Jakarta Struts framework is similar to this design pattern. The
actions are essentially a command treatment.
Stateless session beans can be used to wrap model logic if the com-
mand needs to be distributed.
Distributed commands have been used successfully since the mid-
1980s within the Smalltalk community, and again in many CORBA
communities.
Compound JSPs
D ESCRIPTION : When a command's execution can lead to one of many
pages being returned to the user, sometimes a programmer will express
this decision logic in a JSP .
M OST FREQUENT SCALE : Application.
R EFACTORED SOLUTION NAME : Push decision-making into controllers.
R EFACTORED SOLUTION TYPE : Software.
R EFACTORED SOLUTION DESCRIPTION : The solution is to split the JSP
along the decision lines and branch to separate JSP s in the interaction
controller.
R OOT CAUSES : Ignorance.
S YMPTOMS , CONSEQUENCES : The primary consequence is poor separa-
tion of concerns. JSP code that is difficult to read because of too much
Java can be a symptom of this problem. More than one HTML body or
head tags can be symptomatic of this problem as well. Tools will not
always view Compound JSP s well.
Coarse or Fine Commands
D ESCRIPTION : Commands can be divided too coarsely or finely for opti-
mal performance, readability, or reuse.
M OST FREQUENT SCALE : Application.
R EFACTORED SOLUTION NAME : Optimal command granularity.