Document Information


Part I Introduction

1.  Overview

2.  Using the Tutorial Examples

Part II The Web Tier

3.  Getting Started with Web Applications

4.  Java Servlet Technology

5.  JavaServer Pages Technology

6.  JavaServer Pages Documents

7.  JavaServer Pages Standard Tag Library

8.  Custom Tags in JSP Pages

9.  Scripting in JSP Pages

10.  JavaServer Faces Technology

11.  Using JavaServer Faces Technology in JSP Pages

12.  Developing with JavaServer Faces Technology

13.  Creating Custom UI Components

14.  Configuring JavaServer Faces Applications

15.  Internationalizing and Localizing Web Applications

Part III Web Services

16.  Building Web Services with JAX-WS

17.  Binding between XML Schema and Java Classes

18.  Streaming API for XML

19.  SOAP with Attachments API for Java

Part IV Enterprise Beans

20.  Enterprise Beans

21.  Getting Started with Enterprise Beans

22.  Session Bean Examples

23.  A Message-Driven Bean Example

Part V Persistence

24.  Introduction to the Java Persistence API

25.  Persistence in the Web Tier

26.  Persistence in the EJB Tier

27.  The Java Persistence Query Language

Part VI Services

28.  Introduction to Security in the Java EE Platform

29.  Securing Java EE Applications

30.  Securing Web Applications

31.  The Java Message Service API

32.  Java EE Examples Using the JMS API

33.  Transactions

34.  Resource Connections

Resources and JNDI Naming

Resource Injection

Field-Based Injection

Method-Based Injection

Class-Based Injection

Declaring Multiple Resources

The confirmer Example Application

Running the confirmer Example Application

Creating a Mail Session

Building, Packaging, and Deploying confirmer in NetBeans IDE

Building, Packaging, and Deploying confirmer Using Ant

Running the confirmer Client in NetBeans IDE

Running the confirmer Client Using Ant

Further Information about Resources

35.  Connector Architecture

Part VII Case Studies

36.  The Coffee Break Application

37.  The Duke's Bank Application

Part VIII Appendixes

A.  Java Encoding Schemes

B.  About the Authors



DataSource Objects and Connection Pools

To store, organize, and retrieve data, most applications use a relational database. Java EE 5 components may access relational databases through the JDBC API. For information on this API, see

In the JDBC API, databases are accessed by using DataSource objects. A DataSource has a set of properties that identify and describe the real world data source that it represents. These properties include information such as the location of the database server, the name of the database, the network protocol to use to communicate with the server, and so on. In the Application Server, a data source is called a JDBC resource.

Applications access a data source using a connection, and a DataSource object can be thought of as a factory for connections to the particular data source that the DataSource instance represents. In a basic DataSource implementation, a call to the getConnection method returns a connection object that is a physical connection to the data source.

If a DataSource object is registered with a JNDI naming service, an application can use the JNDI API to access that DataSource object, which can then be used to connect to the data source it represents.

DataSource objects that implement connection pooling also produce a connection to the particular data source that the DataSource class represents. The connection object that the getConnection method returns is a handle to a PooledConnection object rather than being a physical connection. An application uses the connection object in the same way that it uses a connection. Connection pooling has no effect on application code except that a pooled connection, like all connections, should always be explicitly closed. When an application closes a connection that is pooled, the connection is returned to a pool of reusable connections. The next time getConnection is called, a handle to one of these pooled connections will be returned if one is available. Because connection pooling avoids creating a new physical connection every time one is requested, applications can run significantly faster.

A JDBC connection pool is a group of reusable connections for a particular database. Because creating each new physical connection is time consuming, the server maintains a pool of available connections to increase performance. When an application requests a connection, it obtains one from the pool. When an application closes a connection, the connection is returned to the pool.

Applications that use the Persistence API specify the DataSource object they are using in the jta-data-source element of the persistence.xml file.


This is typically the only reference to a JDBC object for a persistence unit. The application code does not refer to any JDBC objects. For more details, see Persistence Units.