accessing DataSource, webapp design question
This is more of a design question. I am using Struts and Tomcat, and have set up a JNDI ref-resource to acquire a DataSource for my database, which works fine. All of my value objects use the same database. The question is how to give each value object access to this DataSource. One option would be to lookup the JNDI contexts once, at application init, and store the DataSource as an application scope attribute. Then whenever a value object needs to do database work, they access this DataSource and do a getConnection() / conn.close(). Another option would be to have each value object do the JNDI lookups (say, in their constructors) and store the DataSource reference in a private field --- then anytime they need to do database work, they use the private field DataSource and do a getConnection() / conn.close() Is there any difference/advantage/disadvantage in having all value objects using the same DataSource reference, stored at application scope, vs. all value objects having their own reference to the DataSource ? Or another approach which is superior to these options ? Thanks, Charlie -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED]
Re: accessing DataSource, webapp design question
The value objects shouldn't know about the ServletContext so you'll need to use JNDI. JNDI doesn't tie your objects to any particular environment. My value objects don't know about the database at all. Each VO has a Mapper (or DAO) associated with it. I configure my mappers with the DataSource so they can persist the objects. This removes all persistence code from the VOs and allows pluggable persistence layers. I'm using JDBC now but could move to EJB, OJB, JDO, etc very easily. David From: Charlie Toohey [EMAIL PROTECTED] Reply-To: Struts Users Mailing List [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: accessing DataSource, webapp design question Date: Wed, 22 Jan 2003 10:31:23 -0800 This is more of a design question. I am using Struts and Tomcat, and have set up a JNDI ref-resource to acquire a DataSource for my database, which works fine. All of my value objects use the same database. The question is how to give each value object access to this DataSource. One option would be to lookup the JNDI contexts once, at application init, and store the DataSource as an application scope attribute. Then whenever a value object needs to do database work, they access this DataSource and do a getConnection() / conn.close(). Another option would be to have each value object do the JNDI lookups (say, in their constructors) and store the DataSource reference in a private field --- then anytime they need to do database work, they use the private field DataSource and do a getConnection() / conn.close() Is there any difference/advantage/disadvantage in having all value objects using the same DataSource reference, stored at application scope, vs. all value objects having their own reference to the DataSource ? Or another approach which is superior to these options ? Thanks, Charlie -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED] _ The new MSN 8: advanced junk mail protection and 2 months FREE* http://join.msn.com/?page=features/junkmail -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED]
Re: accessing DataSource, webapp design question
On Wed, 22 Jan 2003, Charlie Toohey wrote: Date: Wed, 22 Jan 2003 10:31:23 -0800 From: Charlie Toohey [EMAIL PROTECTED] Reply-To: Struts Users Mailing List [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: accessing DataSource, webapp design question This is more of a design question. I am using Struts and Tomcat, and have set up a JNDI ref-resource to acquire a DataSource for my database, which works fine. All of my value objects use the same database. The question is how to give each value object access to this DataSource. One option would be to lookup the JNDI contexts once, at application init, and store the DataSource as an application scope attribute. Then whenever a value object needs to do database work, they access this DataSource and do a getConnection() / conn.close(). Another option would be to have each value object do the JNDI lookups (say, in their constructors) and store the DataSource reference in a private field --- then anytime they need to do database work, they use the private field DataSource and do a getConnection() / conn.close() Is there any difference/advantage/disadvantage in having all value objects using the same DataSource reference, stored at application scope, vs. all value objects having their own reference to the DataSource ? Or another approach which is superior to these options ? A third pattern is actually the recommended one -- do the lookup in your value object every time. It won't matter on Tomcat (which doesn't support these features), but it allows high-availabity servers to support transparent reconfiguration of existing connection pools, or even switching to a backup database, without making you shut down your application. Saving a reference to the connection pool you were given earlier makes all of that kind of support difficult to impossible. Thanks, Charlie Craig -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED]
