Tomcat connection pools and Hibernate

Overview

Tomcat accomplishes connections pooling by defining a resource for a given context. Then that resource is referenced within a web application's web.xml which will cause the Tomcat Resource Factory to create the requested resource and it will be accessible to that web application.

Defining Resources

Resources can be defined in either of the following locations:

Global Context

tomcat/conf/context.xml
All resources defined here can be referenced in any web application.

Context Specific

tomcat/conf/[enginename]/[hostname]/[appcontext].xml
[enginename] This will be Catalina
[hostname] This will usually be localhost
[appcontext] This will be the directory name the application is deployed to under the tomcat/webapp directory.

Following the above directory structure and naming convention allows you define a context and resource that can only be accessed by a specific application. An example would be of this would be tomcat/Catalina/localhost/MyExampleApp.xml

Below is an example of context.xml with a resource defined within. You can also take this example and remove WatchedResource element and use it for a context specific resource.

Web Application Setup

To allow access to the resource you must make a reference to it in your applications web.xml

Hibernate Setup

To configure hibernate to use the resource you reference it using its full JNDI name in the <property name="hibernate.connection.datasource"> tag

Sources:

http://wiki.apache.org/tomcat/TomcatHibernate
http://tomcat.apache.org/tomcat-7.0-doc/jndi-resources-howto.html
http://tomcat.apache.org/tomcat-7.0-doc/jndi-datasource-examples-howto.html