This figure shows the J2EE container architecture in Oracle9iAS. This diagram shows the three tiers: 1) client tier, which has a Web browser loaded on a workstation; 2) the application server on the middle tier, which shows Oracle HTTP Server with its mod_oc4j plug-in that dispatches client requests for J2EE applications that execute in Oracle9iAS Containers for J2EE (OC4J) to the containers. The middle tier also shows the architecture for OC4J, dividing it into the Web container, where JavaServer pages and servlets execute; the enterprise JavaBean (EJB) container, where EJBs execute; the Java APIs, which include: Java Messaging Service (JMS), Java Authentication and Authorization Service (JAAS), Java Transaction API (JTA), JavaMail, JavaBeans Activation Framework (JAF), Java API for XML (JAXP), Java Database Connectivity (JDBC), and the J2EE Connector API; and the Java2 Standard Edition (J2SE) virtual machine; and the back-end, or enterprise data tier, which contains a database.