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Java Servlet & JSP Cookbook by Bruce W. Perry

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21.2. Configuring a DataSource in Tomcat

Problem

You want to configure a javax.sql.DataSource for use in a servlet with the Tomcat web container.

Solution

Create a resource element in Tomcat's server.xml file and an associated resource-ref element in the web.xml deployment descriptor.

Discussion

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:

  1. Create a Resource and a ResourceParams element in server.xml , or in the XML file that you have placed in Tomcat's webapps directory. These elements describe the JNDI object you are creating in order to provide your servlets or JSPs with a DataSource.

  2. Add a resource-ref element to web.xml, which allows the components in the associated web application to access the configured DataSource.

Example 21-2 shows the Resource and a ResourceParams elements in server.xml. This example describes a DataSource that connects with an Oracle 8i database.

Example 21-2. The ...

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