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Re: mapping data

>> If memory serves, one of the architects of JBoss said that the big 
>> bottleneck in a J2EE application is the time spent marshalling and 
>> unmarshalling data that's going to and from a relational database. To 
>> avoid this problem, JBoss caches as much information as it can in Java 
>> objects, and minimizes the number of reads and writes to the database.
Dan Sugalski wrote:
> I do hope it's only caching metadata... I really worry when libraries 
> implement caching in multiuser, potentially distributed database systems.

I think it's caching the data as well.  They've reorganized their Web 
site since I read that white paper (apparently adding a whole bunch of 
broken links, to serve me better), so I can't go back and confirm that.

Note that in J2EE, it's considered chic (if not always practical) to 
never actually write a line of SQL.  You're supposed to use the EJB 
Query Language (which looks remarkably like SQL, except for a few subtle 
differences, such as the absence of a native type for dates) to define 
all the relationships between your entity beans and let the J2EE 
application server take responsibility for setting up your database 
schema and handling all the low-level mapping between the RDBMS and Java