Demystify datasources

Question

Hi, I'm working with adf/bc, 10.1.3.4. After pouring over hundreds of threads in the forum, I'm still a little confused about configuring datasources for an adf application. Some threads seem to even contradict one another, leaving me more confused. So, I've compiled a short list of questions regarding this issue, in hopes I can get some definitive answers:
Initially, we set up our application (modules) to use datasources. For the app module's JDBCDataSource property, we used jdbc/MyAppDS. Then, we created this datasource (globally) on our app server's data-sources.xml. We used the same value (jdbc/MyAppDS) for the jndi-name value of the datasource. This worked just fine.
Recently, however, I was looking at how SRDemo was set up and noticed that it's app module's JDBCDataSource property value (java:comp/env/jdbc/SRDemoDS) was different from that value used for the jndi-name value of the datasource defined in it's data-sources.xml (jdbc/SRDemoDS).
It seems that to use this approach, you need to add the following to web.xml:
<resource-ref>
<res-ref-name>jdbc/SRDemoDS</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
In the guide, [http://download.oracle.com/docs/html/B25947_01/bcservices002.htm#sthref630], it also shows an entry into an application specific orion-web.xml file:
<orion-web-app ... >
<resource-ref-mapping location="jdbc/SRDemoDS" name="jdbc/SRDemoDS"/>
</orion-web-app>
Mine worked without having this orion-web.xml. Also, for the SRDemo application, I commented out all the contents of its orion-web.xml, and it worked as well.
So.... my questions for now are:
1) why wouldn't/shouldn't we use the same value (jdbc/MyAppDS) for both the app module JDBCDataSource property and the jndi-name within data-sources.xml? It seems that this approach works, and we don't need the <resource-ref> entry in the web.xml. I'm sure these things are important, but I'm not seeing the connection here??
2) is there something special about prefixing my app module's JDBCDataSource property with java:comp/env/? Things worked fine when it was just jdbc/MyAppDS??
3) what's the point of having an application specific orion-web.xml with <resource-ref-mapping> if it seems that that app runs the same without it? What role is it playing?
Edited by: kcjim on Feb 4, 2009 2:09 PM

Answer 1

Hi,
i am not an expert either but try as good as I can
+1) why wouldn't/shouldn't we use the same value (jdbc/MyAppDS) for both the app module JDBCDataSource property and the jndi-name within data-sources.xml? It seems that this approach works, and we don't need the <resource-ref> entry in the web.xml. I'm sure these things are important, but I'm not seeing the connection here??+
See: http://java.sun.com/j2ee/1.4/docs/tutorial/doc/Resources2.html
Using "java:comp/env" is the Java EE recommended way
Also this thread is interesting to read: http://forums.java.net/jive/thread.jspa?threadID=14497
+2) is there something special about prefixing my app module's JDBCDataSource property with java:comp/env/? Things worked fine when it was just jdbc/MyAppDS??+
See above.
+3) what's the point of having an application specific orion-web.xml with <resource-ref-mapping> if it seems that that app runs the same without it? What role is it playing?+
The orion-web.xm supercedes web.xml and is not needed for this configuration. However, unlike web.xml, it can be edited from the administration console in OC4J and thus is attractivee to administrators
Frank