By: Emiley J. in Java Tutorials on 2008-11-24
Tomcat makes it easy to set up a connection pool so that servlets and JSPs can efficiently share database connections. In web sites that have many simultaneous users, a connection pool improves efficiency by sharing existing database connections, rather than creating a new connection and tearing it down every time an application has to use the database.
Another benefit of configuring a connection pool is that you can change the database system that a servlet or JSP is using without touching the Java code, because the database resource is configured outside of the servlet or JSP.
Here are the steps for configuring a DataSource with Tomcat:
Create a Resource
Add a resource-ref
Example below shows the Resource and a ResourceParams elements in server.xml. This example describes a DataSource that connects with an Oracle 8i database.
The resource element in server.xml
<Resource name="jdbc/oracle-8i-athletes" scope= "Shareable" type="javax.sql.DataSource" auth= "Container" description="Home Oracle 8i Personal Edition"/> <ResourceParams name="jdbc/oracle-8i-athletes"> <parameter> <name>driverClassName</name> <value>oracle.jdbc.driver.OracleDriver</value> </parameter> <parameter> <name>url</name> <value>jdbc:oracle:thin:@192.168.0.2:1521:ORCL</value> </parameter> <parameter> <name>username</name> <value>scott</value> </parameter> <parameter> <name>password</name> <value>tiger</value> </parameter> </ResourceParams>
Create a Resource and ResourceParams element for each database that your application uses. Example below shows the resource-ref element associated with the Resource specified by example above.
A resource-ref element specifies a DataSource in web.xml
<!-- top of web.xml file --> <resource-ref> <res-ref-name>jdbc/oracle-8i-athletes</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> <!-- rest of web.xml file -->
The JNDI path to this DataSource, which you use in a JNDI lookup (see the next recipe), is jdbc/oracle-8i-athletes.
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