To answer your question, in general, its a very bad idea to
synchronize action methods as that will bring your webapp to a
screeching halt because Struts only creates a single instance of a
given action class. What you will be doing is essentially handling a
single request at a time, very bad.
Now, the reason why you want to synchronize access is based on a bad
design idea. You DO NOT want to have an instance to a database
connection shared between different requests because of the
concurrency issues you refer to. You don't even want to share a
connection within a session for a couple of reasons: you don't want a
connection open across different requests, and even if holding
connections open for a long time isn't bad enough, you can have
multiple client web pages that are part of the same session hitting
the same connection at the same time, which will certainly break
something, and probaly not until your web app is in production :-)
You need to do some research on how to use a connection pool, and then
have your DAOs either get a connection from the connection pool or
take a connection as an argument which will be supplied by the action.
I prefer the latter, that way you can chain operations on the database
in an action without the overhead of each dao call getting and then
freeing a connection from the pool. Also, transactions across DAOs are
much easier with the latter solutions too.
I don't have any links handy, but there's probably at least a
half-dozen pages about this on the Struts wiki that you can find at
http://struts.apache.org/
HTH,
-ed
On 3/21/06, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
Is it a good idea to synchronize DispathAction to make sure all requests
to DB and results which come back don't overstep each other ?
Pls help.
Following is some detail of what am I doing in my application.
I have few operation I want to synchronize.
In my app following steps I am taking
1. calling dispatch Action getInstrumentsFromQ as under, Should
this be synchronized ?
public ActionForward getInstrumentsFromQ(ActionMapping
mapping, ActionForm form, HttpServletRequest request, HttpServletResponse
response) throws Exception {
..
..
}
2. In Dao service I have couple of lists which are stored as Class
variable, where I store one I received from DB.
public class InstrumentDiceQdao extends BaseDao implements
InstrumentDao{
private List instruments =(List )
Collections.synchronizedList(new ArrayList());
private List instrumentDbItems = (List)
Collections.synchronizedList(new ArrayList());
public synchronized List
getAllInstrumentsFromQ(Long sectorId) throws DiceWebException {
...
...
}
}
3. I am putting service object which has results of all DB query
in Session, so I can access from various places in web.
InstrumentService instService = new
InstrumentDaoService(ds) ;
try {
synchronized(instService)
{
List instruments =
instService.getAllinstrumentsFromQ(sectorId);
session.setAttribute(InstrumentService,instService);
}
}
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