The J2EE components, such as EJBs, servlets, and JSPs, included in the J2EE applications on the J2EE server, can connect to the resources, such as databases and OpenTP1. The resource adapter is used to connect to the resources, such as databases and OpenTP1. With Application Server, you can use the resource adapters conforming to the Connector 1.0 specifications or Connector 1.5 specifications. Application Server also provides the functionality for connecting to the resources, such as the SMTP server and JavaBeans resources, without using a resource adapter.
Application Server also provides the connection pooling and transaction management functionality to access the resources with highly efficient and reliable methods. If you use connection pooling, the connections are pooled for resources, and the connections can be used efficiently. Also, the connections with errors are removed from the connection pool appropriately. If you use the transaction management functionality, the transaction manager can properly control the resource access transactions based on the instructions from the transaction attributes and the JTA interface (UserTransaction) specified for each EJB method. A global transaction is used to manage the transactions for multiple resources. If you use a global transaction, you ensure the consistency of updates between resources because the transactions are managed using the two-phase commit protocol.
The following figure shows an example of connecting to the resources using the connection pooling and transaction management functionality.
Figure 3-1 Example of connecting to resources using the connection pooling and transaction management functionality