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regarding connection pool

Rajeev Ravindran
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Joined: Aug 27, 2002
Posts: 455
hi,
im using TOmcat 4.0 with MS-Access as backend..
i tried a conenction pool class found on www.javaexchange.com? ..
it is a servlet which makes the pools,so i invokes this servlet on "<load-on-startup/>" and it works fine...but i have a situation, can i call this servlet instace from a bean..i mean , im using beans for database manipulation and so needs the Connection in the bean..i think one method is to pass the Connection object which i get in the servelt to the constuctor of the bean..is it a good approach ??? does any1 have any other suggestions ???
thnaks,
raj


SCJP, SCWCD, SCBCD, Oracle Certified Professional (SQL n PL/SQL)
Peter den Haan
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Joined: Apr 20, 2000
Posts: 3252
I must say that, based on the materials on the site, I am not impressed by DBConnectionBroker. Today's JDBC API has a standard way of acquiring connections which can be pooled or even part of a distributed transaction: the DataSource. It is standardised, making your application much more portable, and also easier to use: you give a connection back to the pool simply by close()ing it like you do with a normal connection.
So does this answer your question? It does, actually, because your question now becomes: where do I get my DataSource from? There are a number of alternatives.
  • The J2EE way is to ask your application server to set up a DataSource for you. Every app server should be able to do this. This has two advantages: (a) it's the least amount of work and (b) assigning a database to the application becomes a deployment task. You can use JNDI to look up this DataSource anywhere in your application.
  • You can use a connection pool that exposes a DataSource interface, such as Apache Jakarta DBCP. This gives you complete control over how you instantiate it, where you bind it, and so forth.
  • Some JDBC drivers come with a connection pool implementation. Of course this makes you driver-dependent, but often that's OK.
  • Finally, you may sometimes still find that you need a Connection or DataSource in a layer of your application that doesn't have easy access to it. You can pass a Connection as a simple method argumentAlternatively, if you need to make a number of method calls as part of a transaction and want to avoid the Connection cluttering up all your methods, you can use an instance variableAn instance of this FooBarDAO would typically be created as part of an ongoing transaction, and forgotten about once the transaction is complete.
    You would treat a DataSource a bit differently. A DataSource is just a factory for Connection objects and your code needs just a single DataSource that it uses whenever it needs to access the database. You'd use a DataSource if you want the work to be done in an independent transaction (please note that this is not true at all in a managed environment such as an EJB container). You could conceivably use a static variable somewhere to store the DataSource used by your application, but I must admit I don't really like that much; just look the thing up in JNDI at initialisation time if you can.
    Does that help?
    - Peter
    Rajeev Ravindran
    Ranch Hand

    Joined: Aug 27, 2002
    Posts: 455
    hi peter,
    thanks for ur expert advice..i truly appretiate ur instant response..
    peter, does any latest version of Tomcat server has default Connection pool facility ?? as far as i know, Tomcat 4.0, doesnt support Connection pool facility.. if the server handles the connection pool as in Weblogic , its the better option right ??? here my company is sticking on Tomcat, so i shld find an better alternative using Tomcat itself..once again thanks for reply...
    Thanks,
    raj.
    Peter den Haan
    author
    Ranch Hand

    Joined: Apr 20, 2000
    Posts: 3252
    Originally posted by r rajeev:
    peter, does any latest version of Tomcat server has default Connection pool facility ?? as far as i know, Tomcat 4.0, doesnt support Connection pool facility..
    Raj, did you follow the links in my reply above? The second one outlines step by step how to set up a DataSource in Tomcat 4 and bind it in JNDI...
    - Peter
    Rajeev Ravindran
    Ranch Hand

    Joined: Aug 27, 2002
    Posts: 455
    hi peter,
    sorry, my mistake..i checked the 1st and 3rd url, but missed the 2nd one..yep, the 2nd url is the one i was looking for... THANKS
    raj..
    Rajeev Ravindran
    Ranch Hand

    Joined: Aug 27, 2002
    Posts: 455
    hi peter,
    i need ur help again..okey, im working on the connection pool tutorial provided by jakarte..your 2nd url..
    Tomcat DBCP
    now my prob is my DBTest.java is not getting comliled, its throwing 3 errors.
    i wll copy the o/p of my compiler

    i have kept all the jar files in proper place..cld u tell me the name of the jar files which have the DataSouce class and javax.sql.* package ?? from where can i download it ?? i extracted all the jar files in my system to check if the DataSouce class exists in any of them, i found one DataSouce class in activation.jar, but i think that is not the exact jar file which i shld use here coz
    getConnection();
    method is not there in that Class and it throws another error..
    hope my prob is clear for u. plz help..
    thanks,
    raj
    Rajeev Ravindran
    Ranch Hand

    Joined: Aug 27, 2002
    Posts: 455
    sorry sorry, i got the file from somewhere and copiled the file....huh i dont have patience...i wll get back to u if i find any more problems..
    raj
    Peter den Haan
    author
    Ranch Hand

    Joined: Apr 20, 2000
    Posts: 3252
    Originally posted by r rajeev:
    now my prob is my DBTest.java is not getting comliled, its throwing 3 errors.
    If you're still using JDK 1.3, then you need the JDBC Optional Package (as you found out already). JDK 1.4 and above include this as part of the core platform.
    - Peter
    Rajeev Ravindran
    Ranch Hand

    Joined: Aug 27, 2002
    Posts: 455
    hi peter,
    im still facing problems..this time is with configuring server.xml ..its throwing errors
    i have posted my query in Tomcat forum , plz look at it
    Configuring DBCP ??

    Thanks for ur replies,
    raj
     
    Consider Paul's rocket mass heater.
     
    subject: regarding connection pool