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<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">  <head>    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />    <meta http-equiv="Content-Style-Type" content="text/css" />    <title>DataSource Objects and Connection Pools</title>    <link rel="StyleSheet" href="document.css" type="text/css" media="all" />    <link rel="StyleSheet" href="catalog.css" type="text/css" media="all" />    <link rel="Table of Contents" href="J2EETutorialTOC.html" />    <link rel="Previous" href="Resources2.html" />    <link rel="Next" href="Resources4.html" />    <link rel="Index" href="J2EETutorialIX.html" />  </head>  <body>    <table width="550" summary="layout" id="SummaryNotReq1">      <tr>	<td align="left" valign="center">	<font size="-1">	<a href="http://java.sun.com/j2ee/1.4/download.html#tutorial" target="_blank">Download</a>	<br>	<a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/faq.html" target="_blank">FAQ</a>	<br>	<a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/history.html" target="_blank">History</a>	</td>        <td align="center" valign="center"><a accesskey="p" href="Resources2.html"><img id="LongDescNotReq1" src="images/PrevArrow.gif" width="26" height="26" border="0" alt="Prev" /></a><a accesskey="c" href="J2EETutorialFront.html"><img id="LongDescNotReq1" src="images/UpArrow.gif" width="26" height="26" border="0" alt="Home" /></a><a accesskey="n" href="Resources4.html"><img id="LongDescNotReq3" src="images/NextArrow.gif" width="26" height="26" border="0" alt="Next" /></a><a accesskey="i" href="J2EETutorialIX.html"></a>        </td>	<td align="right" valign="center">	<font size="-1">	<a href="http://java.sun.com/j2ee/1.4/docs/api/index.html" target="_blank">API</a>	<br>	<a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/search.html" target="_blank">Search</a>	<br>	<a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/sendusmail.html" target="_blank">Feedback</a></font>	</font>	</td>      </tr>    </table>    <img src="images/blueline.gif" width="550" height="8" ALIGN="BOTTOM" NATURALSIZEFLAG="3" ALT="Divider">    <blockquote><a name="wp80235"> </a><h2 class="pHeading1">DataSource Objects and Connection Pools</h2><a name="wp80259"> </a><p class="pBody">To store, organize, and retrieve data, most applications use a relational database. J2EE components access relational databases through the JDBC 2.0 API. For information on this API, see the JDBC Tutorial:</p><div class="pPreformattedRelative"><pre class="pPreformattedRelative"><a  href="http://java.sun.com/docs/books/tutorial/jdbc" target="_blank">http://java.sun.com/docs/books/tutorial/jdbc</a><a name="wp80241"> </a></pre></div><a name="wp80242"> </a><p class="pBody">In the JDBC API, databases are accessed via <code class="cCode">DataSource</code> objects. A <code class="cCode">DataSource</code> has a set of properties that identify and describe the real world data source that it represents. These properties include information like the location of the database server, the name of the database, the network protocol to use to communicate with the server, and so on. A data source is sometimes referred to as a JDBC resource.</p><a name="wp80243"> </a><p class="pBody">Applications access a data source using a connection, and a <code class="cCode">DataSource</code> object can be thought of as a factory for connections to the particular data source that the <code class="cCode">DataSource</code> instance represents. In a basic <code class="cCode">DataSource</code> implementation, a call to the method <code class="cCode">DataSource.getConnection</code> returns a connection object that is a physical connection to the data source. </p><a name="wp80244"> </a><p class="pBody">If a <code class="cCode">DataSource</code> object is registered with a JNDI naming service, an application can use the JNDI API to access that <code class="cCode">DataSource</code> object, which can then be used to connect to the data source it represents. </p><a name="wp80253"> </a><p class="pBody"><code class="cCode">DataSource</code> objects that implement connection pooling also produce a connection to the particular data source that the <code class="cCode">DataSource</code> class represents. The connection object that the method <code class="cCode">DataSource.getConnection</code> returns is a handle to a <code class="cCode">PooledConnection</code> object rather than being a physical connection. An application uses the connection object like any other 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 <code class="cCode">DataSource.getConnection</code> 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, it can help applications run significantly faster.</p><a name="wp81465"> </a><p class="pBody">The installation process of the J2EE Application Server automatically creates a connection pool named <code class="cCode">PointBasePool</code>. In this book, all of the code examples that access a database use <code class="cCode">DataSource</code> objects that are mapped to <code class="cCode">PointBasePool</code>.</p>    </blockquote>   <img src="images/blueline.gif" width="550" height="8" ALIGN="BOTTOM" NATURALSIZEFLAG="3" ALT="Divider">    <table width="550" summary="layout" id="SummaryNotReq1">      <tr>	<td align="left" valign="center">	<font size="-1">	<a href="http://java.sun.com/j2ee/1.4/download.html#tutorial" target="_blank">Download</a>	<br>	<a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/faq.html" target="_blank">FAQ</a>	<br>	<a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/history.html" target="_blank">History</a>	</td>        <td align="center" valign="center"><a accesskey="p" href="Resources2.html"><img id="LongDescNotReq1" src="images/PrevArrow.gif" width="26" height="26" border="0" alt="Prev" /></a><a accesskey="c" href="J2EETutorialFront.html"><img id="LongDescNotReq1" src="images/UpArrow.gif" width="26" height="26" border="0" alt="Home" /></a><a accesskey="n" href="Resources4.html"><img id="LongDescNotReq3" src="images/NextArrow.gif" width="26" height="26" border="0" alt="Next" /></a><a accesskey="i" href="J2EETutorialIX.html"></a>        </td>	<td align="right" valign="center">	<font size="-1">	<a href="http://java.sun.com/j2ee/1.4/docs/api/index.html" target="_blank">API</a>	<br>	<a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/search.html" target="_blank">Search</a>	<br>	<a href="http://java.sun.com/j2ee/1.4/docs/tutorial/information/sendusmail.html" target="_blank">Feedback</a></font>	</font>	</td>      </tr>    </table>    <img src="images/blueline.gif" width="550" height="8" ALIGN="BOTTOM" NATURALSIZEFLAG="3" ALT="Divider"><p><font size="-1">All of the material in <em>The J2EE(TM) 1.4 Tutorial</em> is <a href="J2EETutorialFront2.html">copyright</a>-protected and may not be published in other workswithout express written permission from Sun Microsystems.</font>  </body></html>
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