source: nutchez-0.1/tomcat/webapps/docs/printer/jndi-datasource-examples-howto.html @ 253

Last change on this file since 253 was 66, checked in by waue, 15 years ago

NutchEz - an easy way to nutch
File size: 46.9 KB
RevLine 
[66]1<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>Apache Tomcat 6.0 - JNDI Datasource HOW-TO</title><meta value="Les Hughes" name="author"><meta value="leslie.hughes@rubus.com" name="email"><meta value="David Haraburda" name="author"><meta value="david-tomcat@haraburda.com" name="email"><meta value="Glenn Nielsen" name="author"><meta value="" name="email"><meta value="Yoav Shapira" name="author"><meta value="yoavs@apache.org" name="email"></head><body vlink="#525D76" alink="#525D76" link="#525D76" text="#000000" bgcolor="#ffffff"><table cellspacing="0" width="100%" border="0"><!--PAGE HEADER--><tr><td><!--PROJECT LOGO--><a href="http://tomcat.apache.org/"><img border="0" alt="
2      The Apache Tomcat Servlet/JSP Container
3    " align="right" src="./../images/tomcat.gif"></a></td><td><font face="arial,helvetica,sanserif"><h1>Apache Tomcat 6.0</h1></font></td><td><!--APACHE LOGO--><a href="http://www.apache.org/"><img border="0" alt="Apache Logo" align="right" src="./../images/asf-logo.gif"></a></td></tr></table><table cellspacing="4" width="100%" border="0"><!--HEADER SEPARATOR--><tr><td colspan="2"><hr size="1" noshade></td></tr><tr><!--RIGHT SIDE MAIN BODY--><td align="left" valign="top" width="80%"><table cellspacing="4" width="100%" border="0"><tr><td valign="top" align="left"><h1>Apache Tomcat 6.0</h1><h2>JNDI Datasource HOW-TO</h2></td><td nowrap="true" valign="top" align="right"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Table of Contents"><strong>Table of Contents</strong></a></font></td></tr><tr><td><blockquote>
4<p>
5<a href="#Introduction">Introduction</a><br>
6<a href="#Database Connection Pool (DBCP) Configurations">
7Database Connection Pool (DBCP) Configurations</a><br>
8<a href="#Non DBCP Solutions">Non DBCP Solutions</a><br>
9<a href="#Oracle 8i with OCI client">Oracle 8i with OCI client</a><br>
10<a href="#Common Problems">Common Problems</a><br>
11</p>
12</blockquote></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Introduction"><strong>Introduction</strong></a></font></td></tr><tr><td><blockquote>
13
14<p>JNDI Datasource configuration is covered extensively in the
15JNDI-Resources-HOWTO.  However, feedback from <code>tomcat-user</code> has
16shown that specifics for individual configurations can be rather tricky.</p>
17
18<p>Here then are some example configurations that have been posted to
19tomcat-user for popular databases and some general tips for db useage.</p>
20
21<p>You should be aware that since these notes are derived from configuration
22and/or feedback posted to <code>tomcat-user</code> YMMV :-). Please let us
23know if you have any other tested configurations that you feel may be of use
24to the wider audience, or if you feel we can improve this section in anyway.</p>
25
26<p>
27<b>Please note that JNDI resource configuration changed somewhat between
28Tomcat 5.0.x and Tomcat 5.5.x.</b>  You will most likely need to modify older
29JNDI resource configurations to match the syntax in the example below in order
30to make them work in Tomcat 6.x.x.
31</p>
32
33<p>
34Also, please note that JNDI DataSource configuration in general, and this
35tutorial in particular, assumes that you have read and understood the
36<a href="../config/context.html">Context</a> and
37<a href="../config/host.html">Host</a> configuration references, including
38the section about Automatic Application Deployment in the latter reference.
39</p>
40</blockquote></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Database Connection Pool (DBCP) Configurations"><strong>Database Connection Pool (DBCP) Configurations</strong></a></font></td></tr><tr><td><blockquote>
41
42<p>DBCP provides support for JDBC 2.0.  On systems using a 1.4 JVM DBCP
43will support JDBC 3.0. Please let us know if you have used DBCP and its
44JDBC 3.0 features with a 1.4 JVM.
45</p>
46
47<p>See the <a href="http://jakarta.apache.org/commons/dbcp/configuration.html">
48DBCP documentation</a> for a complete list of configuration parameters.
49</p>
50
51<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Installation"><strong>Installation</strong></a></font></td></tr><tr><td><blockquote>
52<p>DBCP uses the Jakarta-Commons Database Connection Pool. It relies on
53number of Jakarta-Commons components:
54<ul>
55<li>Jakarta-Commons DBCP</li>
56<li>Jakarta-Commons Collections</li>
57<li>Jakarta-Commons Pool</li>
58</ul>
59These libraries are located in a single JAR at
60<code>$CATALINA_HOME/lib/tomcat-dbcp.jar</code>. However,
61only the classes needed for connection pooling have been included, and the
62packages have been renamed to avoid interfering with applications.
63</p>
64
65</blockquote></td></tr></table>
66
67<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Preventing dB connection pool leaks"><strong>Preventing dB connection pool leaks</strong></a></font></td></tr><tr><td><blockquote>
68
69<p>
70A database connection pool creates and manages a pool of connections
71to a database. Recycling and reusing already existing connections
72to a dB is more efficient than opening a new connection.
73</p>
74
75<p>
76There is one problem with connection pooling.  A web application has
77to explicetely close ResultSet's, Statement's, and Connection's.
78Failure of a web application to close these resources can result in
79them never being available again for reuse, a db connection pool "leak".
80This can eventually result in your web application db connections failing
81if there are no more available connections.</p>
82
83<p>
84There is a solution to this problem.  The Jakarta-Commons DBCP can be
85configured to track and recover these abandoned dB connections.  Not
86only can it recover them, but also generate a stack trace for the code
87which opened these resources and never closed them.</p>
88
89<p>
90To configure a DBCP DataSource so that abandoned dB connections are
91removed and recycled add the following attribute to the
92<code>Resource</code> configuration for your DBCP DataSource:
93<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
94            removeAbandoned="true"
95</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
96When available db connections run low DBCP will recover and recyle
97any abandoned dB connections it finds. The default is <code>false</code>.
98</p>
99
100<p>
101Use the <code>removeAbandonedTimeout</code> attribute to set the number
102of seconds a dB connection has been idle before it is considered abandoned.
103<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
104            removeAbandonedTimeout="60"
105</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
106The default timeout for removing abandoned connections is 300 seconds.
107</p>
108
109<p>
110The <code>logAbandoned</code> attribute can be set to <code>true</code>
111if you want DBCP to log a stack trace of the code which abandoned the
112dB connection resources.
113<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
114            logAbandoned="true"
115</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
116The default is <code>false</code>.
117</p>
118
119</blockquote></td></tr></table>
120
121<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="MySQL DBCP Example"><strong>MySQL DBCP Example</strong></a></font></td></tr><tr><td><blockquote>
122
123<h3>0. Introduction</h3>
124<p>Versions of <a href="http://www.mysql.com/products/mysql/index.html">MySQL</a> and JDBC drivers that have been reported to work:
125<ul>
126<li>MySQL 3.23.47, MySQL 3.23.47 using InnoDB,, MySQL 3.23.58,  MySQL 4.0.1alpha</li>
127<li><a href="http://www.mysql.com/products/connector-j">Connector/J</a> 3.0.11-stable (the official JDBC Driver)</li>
128<li><a href="http://mmmysql.sourceforge.net">mm.mysql</a> 2.0.14 (an old 3rd party JDBC Driver)</li>
129</ul>
130</p>
131
132<p>Before you proceed, don't forget to copy the JDBC Driver's jar into <code>$CATALINA_HOME/lib</code>.</p>
133
134<h3>1. MySQL configuration</h3>
135<p>
136Ensure that you follow these instructions as variations can cause problems.
137</p>
138
139<p>Create a new test user, a new database and a single test table.
140Your MySQL user <strong>must</strong> have a password assigned. The driver
141will fail if you try to connect with an empty password.
142<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
143mysql&gt; GRANT ALL PRIVILEGES ON *.* TO javauser@localhost
144    -&gt;   IDENTIFIED BY 'javadude' WITH GRANT OPTION;
145mysql&gt; create database javatest;
146mysql&gt; use javatest;
147mysql&gt; create table testdata (
148    -&gt;   id int not null auto_increment primary key,
149    -&gt;   foo varchar(25),
150    -&gt;   bar int);
151</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
152<blockquote>
153<strong>Note:</strong> the above user should be removed once testing is
154complete!
155</blockquote>
156</p>
157
158<p>Next insert some test data into the testdata table.
159<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
160mysql&gt; insert into testdata values(null, 'hello', 12345);
161Query OK, 1 row affected (0.00 sec)
162
163mysql&gt; select * from testdata;
164+----+-------+-------+
165| ID | FOO   | BAR   |
166+----+-------+-------+
167|  1 | hello | 12345 |
168+----+-------+-------+
1691 row in set (0.00 sec)
170
171mysql&gt;
172</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
173</p>
174
175<h3>2. Context configuration</h3>
176<p>Configure the JNDI DataSource in Tomcat by adding a declaration for your
177resource to your <a href="../config/context.html">Context</a>.</p>
178<p>For example:
179
180<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
181&lt;Context path="/DBTest" docBase="DBTest"
182        debug="5" reloadable="true" crossContext="true"&gt;
183
184    &lt;!-- maxActive: Maximum number of dB connections in pool. Make sure you
185         configure your mysqld max_connections large enough to handle
186         all of your db connections. Set to -1 for no limit.
187         --&gt;
188
189    &lt;!-- maxIdle: Maximum number of idle dB connections to retain in pool.
190         Set to -1 for no limit.  See also the DBCP documentation on this
191         and the minEvictableIdleTimeMillis configuration parameter.
192         --&gt;
193
194    &lt;!-- maxWait: Maximum time to wait for a dB connection to become available
195         in ms, in this example 10 seconds. An Exception is thrown if
196         this timeout is exceeded.  Set to -1 to wait indefinitely.
197         --&gt;
198
199    &lt;!-- username and password: MySQL dB username and password for dB connections  --&gt;
200
201    &lt;!-- driverClassName: Class name for the old mm.mysql JDBC driver is
202         org.gjt.mm.mysql.Driver - we recommend using Connector/J though.
203         Class name for the official MySQL Connector/J driver is com.mysql.jdbc.Driver.
204         --&gt;
205   
206    &lt;!-- url: The JDBC connection url for connecting to your MySQL dB.
207         The autoReconnect=true argument to the url makes sure that the
208         mm.mysql JDBC Driver will automatically reconnect if mysqld closed the
209         connection.  mysqld by default closes idle connections after 8 hours.
210         --&gt;
211
212  &lt;Resource name="jdbc/TestDB" auth="Container" type="javax.sql.DataSource"
213               maxActive="100" maxIdle="30" maxWait="10000"
214               username="javauser" password="javadude" driverClassName="com.mysql.jdbc.Driver"
215               url="jdbc:mysql://localhost:3306/javatest?autoReconnect=true"/&gt;
216
217&lt;/Context&gt;
218</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
219</p>
220
221<h3>3. web.xml configuration</h3>
222
223<p>Now create a <code>WEB-INF/web.xml</code> for this test application.
224<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
225&lt;web-app xmlns="http://java.sun.com/xml/ns/j2ee"
226    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
227    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
228http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
229    version="2.4"&gt;
230  &lt;description&gt;MySQL Test App&lt;/description&gt;
231  &lt;resource-ref&gt;
232      &lt;description&gt;DB Connection&lt;/description&gt;
233      &lt;res-ref-name&gt;jdbc/TestDB&lt;/res-ref-name&gt;
234      &lt;res-type&gt;javax.sql.DataSource&lt;/res-type&gt;
235      &lt;res-auth&gt;Container&lt;/res-auth&gt;
236  &lt;/resource-ref&gt;
237&lt;/web-app&gt;
238</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
239</p>
240
241<h3>4. Test code</h3>
242<p>Now create a simple <code>test.jsp</code> page for use later.
243<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
244&lt;%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql" %&gt;
245&lt;%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %&gt;
246
247&lt;sql:query var="rs" dataSource="jdbc/TestDB"&gt;
248select id, foo, bar from testdata
249&lt;/sql:query&gt;
250
251&lt;html&gt;
252  &lt;head&gt;
253    &lt;title&gt;DB Test&lt;/title&gt;
254  &lt;/head&gt;
255  &lt;body&gt;
256
257  &lt;h2&gt;Results&lt;/h2&gt;
258 
259&lt;c:forEach var="row" items="${rs.rows}"&gt;
260    Foo ${row.foo}&lt;br/&gt;
261    Bar ${row.bar}&lt;br/&gt;
262&lt;/c:forEach&gt;
263
264  &lt;/body&gt;
265&lt;/html&gt;
266</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
267</p>
268
269<p>That JSP page makes use of <a href="http://java.sun.com/products/jsp/jstl">JSTL</a>'s SQL and Core taglibs. You can get it from Sun's <a href="http://java.sun.com/webservices/downloads/webservicespack.html">Java Web Services Developer Pack</a> or <a href="http://jakarta.apache.org/taglibs/doc/standard-doc/intro.html">Jakarta Taglib Standard 1.1</a> project - just make sure you get a 1.1.x release. Once you have JSTL, copy <code>jstl.jar</code> and <code>standard.jar</code> to your web app's <code>WEB-INF/lib</code> directory.
270
271</p>
272
273<p>Finally deploy your web app into <code>$CATALINA_BASE/webapps</code> either
274as a warfile called <code>DBTest.war</code> or into a sub-directory called
275<code>DBTest</code></p>
276<p>Once deployed, point a browser at
277<code>http://localhost:8080/DBTest/test.jsp</code> to view the fruits of
278your hard work.</p>
279
280</blockquote></td></tr></table>
281
282<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Oracle 8i, 9i & 10g"><strong>Oracle 8i, 9i &amp; 10g</strong></a></font></td></tr><tr><td><blockquote>
283<h3>0.    Introduction</h3>
284
285<p>Oracle requires minimal changes from the MySQL configuration except for the
286usual gotchas :-)</p>
287<p>Drivers for older Oracle versions may be distributed as *.zip files rather
288than *.jar files. Tomcat will only use <code>*.jar</code> files installed in
289<code>$CATALINA_HOME/lib</code>. Therefore <code>classes111.zip</code>
290or <code>classes12.zip</code> will need to be renamed with a <code>.jar</code>
291extension. Since jarfiles are zipfiles, there is no need to unzip and jar these
292files - a simple rename will suffice.</p>
293
294<p>For Oracle 9i onwards you should use <code>oracle.jdbc.OracleDriver</code>
295rather than <code>oracle.jdbc.driver.OracleDriver</code> as Oracle have stated
296that <code>oracle.jdbc.driver.OracleDriver</code> is deprecated and support
297for this driver class will be discontinued in the next major release.
298</p>
299
300<h3>1. Context configuration</h3>
301<p>In a similar manner to the mysql config above, you will need to define your
302Datasource in your <a href="../config/context.html">Context</a>. Here we define a
303Datasource called myoracle using the thin driver to connect as user scott,
304password tiger to the sid called mysid. (Note: with the thin driver this sid is
305not the same as the tnsname). The schema used will be the default schema for the
306user scott.</p>
307
308<p>Use of the OCI driver should simply involve a changing thin to oci in the URL string.
309<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
310&lt;Resource name="jdbc/myoracle" auth="Container"
311              type="javax.sql.DataSource" driverClassName="oracle.jdbc.OracleDriver"
312              url="jdbc:oracle:thin:@127.0.0.1:1521:mysid"
313              username="scott" password="tiger" maxActive="20" maxIdle="10"
314              maxWait="-1"/&gt; 
315</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
316</p>
317
318<h3>2.    web.xml configuration</h3>
319<p>You should ensure that you respect the element ordering defined by the DTD when you
320create you applications web.xml file.</p>
321<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
322&lt;resource-ref&gt;
323 &lt;description&gt;Oracle Datasource example&lt;/description&gt;
324 &lt;res-ref-name&gt;jdbc/myoracle&lt;/res-ref-name&gt;
325 &lt;res-type&gt;javax.sql.DataSource&lt;/res-type&gt;
326 &lt;res-auth&gt;Container&lt;/res-auth&gt;
327&lt;/resource-ref&gt;
328</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
329<h3>3.   Code example</h3>
330<p>You can use the same example application as above (asuming you create the required DB
331instance, tables etc.) replacing the Datasource code with something like</p>
332<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
333Context initContext = new InitialContext();
334Context envContext  = (Context)initContext.lookup("java:/comp/env");
335DataSource ds = (DataSource)envContext.lookup("jdbc/myoracle");
336Connection conn = ds.getConnection();
337//etc.
338</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
339</blockquote></td></tr></table>
340
341
342<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="PostgreSQL"><strong>PostgreSQL</strong></a></font></td></tr><tr><td><blockquote>
343<h3>0.    Introduction</h3>
344<p>PostgreSQL is configured in a similar manner to Oracle.</p>
345
346<h3>1. Required files </h3>
347<p>
348Copy the Postgres JDBC jar to $CATALINA_HOME/lib. As with Oracle, the
349jars need to be in this directory in order for DBCP's Classloader to find
350them. This has to be done regardless of which configuration step you take next.
351</p>
352
353<h3>2. Resource configuration</h3>
354
355<p>
356You have two choices here: define a datasource that is shared across all Tomcat
357applications, or define a datasource specifically for one application.
358</p>
359
360<h4>2a. Shared resource configuration</h4>
361<p>
362Use this option if you wish to define a datasource that is shared across
363multiple Tomcat applications, or if you just prefer defining your datasource
364in this file.
365</p>
366<p><i>This author has not had success here, although others have reported so.
367Clarification would be appreciated here.</i></p>
368
369<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
370&lt;Resource name="jdbc/postgres" auth="Container"
371          type="javax.sql.DataSource" driverClassName="org.postgresql.Driver"
372          url="jdbc:postgresql://127.0.0.1:5432/mydb"
373          username="myuser" password="mypasswd" maxActive="20" maxIdle="10" maxWait="-1"/&gt;
374</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
375<h4>2b. Application-specific resource configuration</h4>
376
377<p>
378Use this option if you wish to define a datasource specific to your application,
379not visible to other Tomcat applications. This method is less invasive to your
380Tomcat installation.
381</p>
382
383<p>
384Create a resource definition for your <a href="../config/context.html">Context</a>.
385The Context element should look something like the following.
386</p>
387
388<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
389&lt;Context path="/someApp" docBase="someApp"
390   crossContext="true" reloadable="true" debug="1"&gt;
391
392&lt;Resource name="jdbc/postgres" auth="Container"
393          type="javax.sql.DataSource" driverClassName="org.postgresql.Driver"
394          url="jdbc:postgresql://127.0.0.1:5432/mydb"
395          username="myuser" password="mypasswd" maxActive="20" maxIdle="10"
396maxWait="-1"/&gt;
397&lt;/Context&gt;
398</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
399
400<h3>3. web.xml configuration</h3>
401<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
402&lt;resource-ref&gt;
403 &lt;description&gt;postgreSQL Datasource example&lt;/description&gt;
404 &lt;res-ref-name&gt;jdbc/postgres&lt;/res-ref-name&gt;
405 &lt;res-type&gt;javax.sql.DataSource&lt;/res-type&gt;
406 &lt;res-auth&gt;Container&lt;/res-auth&gt;
407&lt;/resource-ref&gt;
408</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
409
410<h4>4. Accessing the datasource</h4>
411<p>
412When accessing the datasource programmatically, remember to prepend
413<code>java:/comp/env</code> to your JNDI lookup, as in the following snippet of
414code. Note also that "jdbc/postgres" can be replaced with any value you prefer, provided
415you change it in the above resource definition file as well.
416</p>
417
418<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
419InitialContext cxt = new InitialContext();
420if ( cxt == null ) {
421   throw new Exception("Uh oh -- no context!");
422}
423
424DataSource ds = (DataSource) cxt.lookup( "java:/comp/env/jdbc/postgres" );
425
426if ( ds == null ) {
427   throw new Exception("Data source not found!");
428}
429</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
430
431</blockquote></td></tr></table>
432</blockquote></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Non-DBCP Solutions"><strong>Non-DBCP Solutions</strong></a></font></td></tr><tr><td><blockquote>
433<p>
434These solutions either utilise a single connection to the database (not recommended for anything other
435than testing!) or some other pooling technology.
436</p>
437</blockquote></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Oracle 8i with OCI client"><strong>Oracle 8i with OCI client</strong></a></font></td></tr><tr><td><blockquote>
438<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Introduction"><strong>Introduction</strong></a></font></td></tr><tr><td><blockquote>
439<p>Whilst not strictly addressing the creation of a JNDI DataSource using the OCI client, these notes can be combined with the
440Oracle and DBCP solution above.</p>
441<p>
442In order to use OCI driver, you should have an Oracle client installed. You should have installed
443Oracle8i(8.1.7) client from cd,  and download the suitable JDBC/OCI
444driver(Oracle8i 8.1.7.1 JDBC/OCI Driver) from <a href="http://otn.oracle.com/">otn.oracle.com</a>.
445</p>
446<p>
447After renaming <code>classes12.zip</code> file to <code>classes12.jar</code>
448for Tomcat, copy it into <code>$CATALINA_HOME/lib</code>.
449You may also have to remove the <code>javax.sql.*</code> classes
450from this file depending upon the version of Tomcat and JDK you are using.
451</p>
452</blockquote></td></tr></table>
453
454<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Putting it all together"><strong>Putting it all together</strong></a></font></td></tr><tr><td><blockquote>
455<p>
456Ensure that you have the <code>ocijdbc8.dll</code> or <code>.so</code> in your <code>$PATH</code> or <code>LD_LIBRARY_PATH</code>
457 (possibly in <code>$ORAHOME\bin</code>) and also confirm that the native library can be loaded by a simple test program
458using <code>System.loadLibrary("ocijdbc8");</code>
459</p>
460<p>
461You should next create a simple test servlet or jsp that has these
462<strong>critical lines</strong>:
463</p>
464<div align="left"><table border="0" cellpadding="0" cellspacing="4"><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#ffffff"><pre>
465DriverManager.registerDriver(new
466oracle.jdbc.driver.OracleDriver());
467conn =
468DriverManager.getConnection("jdbc:oracle:oci8:@database","username","password");
469</pre></td><td width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr><tr><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td><td height="1" width="1" bgcolor="#023264"><img border="0" hspace="0" vspace="0" height="1" width="1" src="./../images/void.gif"></td></tr></table></div>
470<p>
471where database is of the form <code>host:port:SID</code> Now if you try to access the URL of your
472test servlet/jsp and what you get is a
473<code>ServletException</code> with a root cause of <code>java.lang.UnsatisfiedLinkError:get_env_handle</code>.
474</p>
475<p>
476First, the <code>UnsatisfiedLinkError</code> indicates that you have
477<ul>
478<li>a mismatch between your JDBC classes file and
479your Oracle client version. The giveaway here is the message stating that a needed library file cannot be
480found. For example, you may be using a classes12.zip file from Oracle Version 8.1.6 with a Version 8.1.5
481Oracle client. The classeXXXs.zip file and Oracle client software versions must match.
482</li>
483<li>A <code>$PATH</code>, <code>LD_LIBRARY_PATH</code> problem.</li>
484<li>It has been reported that ignoring the driver you have downloded from otn and using
485the classes12.zip file from the directory <code>$ORAHOME\jdbc\lib</code> will also work.
486</li>
487</ul>
488</p>
489<p>
490Next you may experience the error <code>ORA-06401 NETCMN: invalid driver designator</code>
491</p>
492<p>
493The Oracle documentation says : "Cause: The login (connect) string contains an invalid
494driver designator. Action: Correct the string and re-submit."
495
496Change the database connect string (of the form <code>host:port:SID</code>) with this one:
497<code>(description=(address=(host=myhost)(protocol=tcp)(port=1521))(connect_data=(sid=orcl)))</code>
498</p>
499<p>
500<i>Ed. Hmm, I don't think this is really needed if you sort out your TNSNames - but I'm not an Oracle DBA :-)</i>
501</p>
502</blockquote></td></tr></table>
503</blockquote></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Common Problems"><strong>Common Problems</strong></a></font></td></tr><tr><td><blockquote>
504<p>Here are some common problems encountered with a web application which
505uses a database and tips for how to solve them.</p>
506
507<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Intermittent dB Connection Failures"><strong>Intermittent dB Connection Failures</strong></a></font></td></tr><tr><td><blockquote>
508<p>
509Tomcat runs within a JVM.  The JVM periodically performs garbage collection
510(GC) to remove java objects which are no longer being used.  When the JVM
511performs GC execution of code within Tomcat freezes. If the maximum time
512configured for establishment of a dB connection is less than the amount
513of time garbage collection took you can get a db conneciton failure.
514</p>
515
516<p>To collect data on how long garbage collection is taking add the
517<code>-verbose:gc</code> argument to your <code>CATALINA_OPTS</code>
518environment variable when starting Tomcat.  When verbose gc is enabled
519your <code>$CATALINA_BASE/logs/catalina.out</code> log file will include
520data for every garbage collection including how long it took.</p>
521
522<p>When your JVM is tuned correctly 99% of the time a GC will take less
523than one second.  The remainder will only take a few seconds.  Rarely,
524if ever should a GC take more than 10 seconds.</p>
525
526<p>Make sure that the db connection timeout is set to 10-15 seconds.
527For the DBCP you set this using the parameter <code>maxWait</code>.</p>
528
529</blockquote></td></tr></table>
530
531<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Random Connection Closed Exceptions"><strong>Random Connection Closed Exceptions</strong></a></font></td></tr><tr><td><blockquote>
532<p>
533These can occur when one request gets a db connection from the connection
534pool and closes it twice.  When using a connection pool, closing the
535connection just returns it to the pool for reuse by another request,
536it doesn't close the connection.  And Tomcat uses multiple threads to
537handle concurrent requests. Here is an example of the sequence
538of events which could cause this error in Tomcat:
539<pre>
540  Request 1 running in Thread 1 gets a db connection.
541
542  Request 1 closes the db connection.
543
544  The JVM switches the running thread to Thread 2
545
546  Request 2 running in Thread 2 gets a db connection
547  (the same db connection just closed by Request 1).
548
549  The JVM switches the running thread back to Thread 1
550
551  Request 1 closes the db connection a second time in a finally block.
552
553  The JVM switches the running thread back to Thread 2
554
555  Request 2 Thread 2 tries to use the db connection but fails
556  because Request 1 closed it.
557</pre>
558Here is an example of properly written code to use a db connection
559obtained from a connection pool:
560<pre>
561  Connection conn = null;
562  Statement stmt = null;  // Or PreparedStatement if needed
563  ResultSet rs = null;
564  try {
565    conn = ... get connection from connection pool ...
566    stmt = conn.createStatement("select ...");
567    rs = stmt.executeQuery();
568    ... iterate through the result set ...
569    rs.close();
570    rs = null;
571    stmt.close();
572    stmt = null;
573    conn.close(); // Return to connection pool
574    conn = null;  // Make sure we don't close it twice
575  } catch (SQLException e) {
576    ... deal with errors ...
577  } finally {
578    // Always make sure result sets and statements are closed,
579    // and the connection is returned to the pool
580    if (rs != null) {
581      try { rs.close(); } catch (SQLException e) { ; }
582      rs = null;
583    }
584    if (stmt != null) {
585      try { stmt.close(); } catch (SQLException e) { ; }
586      stmt = null;
587    }
588    if (conn != null) {
589      try { conn.close(); } catch (SQLException e) { ; }
590      conn = null;
591    }
592  }
593</pre>
594</p>
595
596</blockquote></td></tr></table>
597
598<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Context versus GlobalNamingResources"><strong>Context versus GlobalNamingResources</strong></a></font></td></tr><tr><td><blockquote>
599<p>
600  Please note that although the above instructions place the JNDI declarations in a Context
601  element, it is possible and sometimes desirable to place these declarations in the
602  <a href="../config/globalresources.html">GlobalNamingResources</a> section of the server
603  configuration file.  A resource placed in the GlobalNamingResources section will be shared
604  among the Contexts of the server.
605</p>
606</blockquote></td></tr></table>
607
608<table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="JNDI Resource Naming and Realm Interaction"><strong>JNDI Resource Naming and Realm Interaction</strong></a></font></td></tr><tr><td><blockquote>
609<p>
610  In order to get Realms to work, the realm must refer to the datasource as
611  defined in the &lt;GlobalNamingResources&gt; or &lt;Context&gt; section, not a datasource as renamed
612  using &lt;ResourceLink&gt;.
613</p>
614</blockquote></td></tr></table> 
615
616</blockquote></td></tr></table></td></tr><!--FOOTER SEPARATOR--><tr><td colspan="2"><hr size="1" noshade></td></tr><!--PAGE FOOTER--><tr><td colspan="2"><div align="center"><font size="-1" color="#525D76"><em>
617        Copyright &copy; 1999-2008, Apache Software Foundation
618        </em></font></div></td></tr></table></body></html>
Note: See TracBrowser for help on using the repository browser.