This figure shows the logical architecture of Oracle Application Server J2EE components. It identifies the various layers in the container: JMX, Web Services, EJB container, Servlet container, JCA container, TopLink Persistence layer, and other J2EE services. The OC4J instances run in the JDK 1.4.2 or 1.5 environment. In addition to the OC4J container, an OC4J instance also contains a JMS router, Application Server Control component, Rules engine component, and the default J2EE application.