enum

Once upon a time Very Clever Hare met Hedgehog Inside-Out. Hedgehog was thin, had dark circles under his eyes, and it was apparent that these needles made his life miserable. Very Clever Hare looked at the hedgehog sympathetically and decided he wanted to help him somehow.
“You know, I can’t listen to loud music loudly. I can only do that with quiet music.” said Very Clever Hare. He was trying to build a psychological bridge through a common non-trivial talk subject.
Hedgehog pulled tiny, almost invisible headphone’s earplugs out of his ears and said thoughtfully:
“Pardon me?”
“There are only two adequate finite dimensional algebras over the real numbers field. I can’t believe there are only two!” - hare suddenly changed the subject to the one that he was really interested in. As with any very clever hare, he was really busy with his own problems and had only a very short attention span to someone else’s troubles.
Hedgehog looked at the hare as people would look at a strange kettle. On one side, their belief that the future is bright makes them wait for the kettle to boil while, on the other side, their intuition tells them that enjoying a fresh cup of a tea is a very distant possibility.
“Maybe there are just two. But something will still be wrong with them. Even if they are adequate” replied Hedgehog Inside-Out.
Hare sat on his rudimentary tail and returned the look. Hedgehog slowly pulled a pack of cigarettes from his pocket, gave one to hare, they lit them and were sitting quietly for the next five minutes…

(translated from my original Russian version and available at Exceeder's LJ)

Recent JDJ's article starts with:
"Is middleware becoming commoditized, as Sun's Jonathan Schwartz contends? Or is it a continuing growth area, as "professional open source" advocate Marc Fleury, CEO of JBoss Inc., maintains?"

I totally agree with Marc. I believe, middleware just went to be good enough to make sense in variety of applications. But it is far, in fact very far, from being good, let alone to be at the full potenital. Architects and developers just start to realize how to organize middleware so it becomes a stable interconnected solution provider instead of disconnected islands of data encapsulation. I expect some revolutionizing concepts coming from this area in the near future - the way window systems revolutionized UI, I believe we are staying in front of the new way of organizing servers.

The following pattern proves to be useful, if you want to expose your application tier to some scripting language. It will gain you a lot, if you deal with table-like structures and would like to unify the interface (lists of users, records, documents etc. where number of columns and details are varying).

RowSet interface was introduced in JDK 1.4 in javax.sql as a Bean-like access to JDBC resources. It somewhat resembles DataSet from the win32 world. This is a stripped-down version of any RowSet, that demonstrates its basic behaviour:

1 interface SimpleRowSet 
2 { 
3     void execute(String command); 
4     boolean next(); 
5     String[] columns(); 
6     String getString(int column); 
7 }

Once your application have implemented this interface, you can use it from within your JSP as a session bean.

Following JSP code demonstrates an implementation (for simplicity of understanding, I have used custom tag library):
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The question is really not so simple. Many things have proven to be myths:
- EJBs are inherently slow. Slow means nothing in programmer's world and given a server cluster with a high load of users I want to see your JDBC code performing this well
- EJBs are buggy. Not anymore - the technology has matured.
- EJBs are difficult to debug - not really. But not as simple as plain Java standalone code.
- there is not enough functionality in EJBs that I need from my persistence layer. This is true. If you are absolutely sure there is not enough, you might be right.

Because ( Read more...Collapse )