Hi Edla,
I'm hesitant in posting codes I developed for my company, but I'm more than
willing to discuss my general strategies. Our EJB architecture and designs
runs contrary to most others you will find; our entity beans are BMP and
fine-grained, mapping one-to-one with each of our SQL tables (as a matter
of fact, I wrote a custom EJBMaker that takes a sql ddl and creates all the
necessary EJBHome, EJBObject and Bean classese as well as the xml dd's, but
that's another story! ;-))
What our architecture does emphasize that's consistent with many others is
the session-bean facade pattern; any bean client of ours hit only session
beans, which in turn hit entity. This enlargens the transaction scope,
allowing the bean container more "space" in doing optimization tricks like
caching, etc...
Because our entity beans are fine-grained, and are all wrapped by session
beans, the task of writing these session beans simply to call all the
accessor method of each entity EJBObject and all finder methods of each
entity EJBHome can get tedious. So this is where reflection comes in: by
having our session beans delegate to reflection-based entity proxies, we
save a lot of time in physically coding these facades.
But in order to count on reflection to do your dirty work, you need to
adhere to strict nomenclature. For example, all our sql tables are named
after a business object (e.g. member, node, permission), and my EJBMaker
creates entity beans based on these names (Member, MemberKey, getMemberName,
etc...) In our case we also use a lot of link tables (member_node,
member_permission, etc..), which just contain 2 columns of two foreign keys;
these tables are mapped to corresponding entity beans MemberNode and
MemberPermission. Instead of physically coding a session bean that deals
with each link entity bean separately, I used reflection with a method like:
void createLink(String functionName, long assigmentID, long targetID);
where the functionName can be "Member2Node", "Node2Permission", etc... The
function delegates to a reflection based proxy that parses the function
name, retrieves the corresponding EJBHomes, dynamically constructs the
primary key instances, and invokes the correct EJBHome.create() method.
This same technique is used for removing a link and finding a link.
So as you can see, reflection, if used wisely, can save you a lot of work.
But don't overuse it unless you know what you're doing, for it is very
difficult to debug, and even more difficult for your fellow coworkers to
read!
Gene
-----Original Message-----
From: A mailing list for Enterprise JavaBeans development
To: [EMAIL PROTECTED]
Sent: 1/9/01 8:12 PM
Subject: Re: Please comment: Using java.lang.reflect to simplify database
access
Hi Chuang,
Can u explain me how to use Reflection classess in the session bean to
reduce the code redundancy, and if possible could u send me the code of
session bean where u used this and in what other context we can use
this?
Thanks
Edla B. Reddy
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