Environment tags configure class-loaders, logging, authentication and resources like databases, JMS queues, EJB servers, and web service clients. Many of the resources are stored in JNDI or in EL variables for later assembly.

Any environment resource can appear in any of Resin environments: <resin>, <cluster>, <host> and <web-app>. Resources configured at parent levels are shared among all children, so a database can share connection pools for all web-apps or an authenticator can provide single-signon.