<!-- inside server.xml -->
<Context path="/myApp">
        <Resource name="jdbc/testdb" auth="Container"
                type="javax.sql.DataSource" driverClassName="org.postgresql.Driver"
                url="jdbc:postgresql://localhost:5432/testdb"
                username="postgres" password="" maxActive="20" maxIdle="10" maxWait="-1"
        />
</Context>


<!-- inside web.xml -->
<resource-ref>
 <description>postgreSQL Datasource example</description>
 <res-ref-name>jdbc/testdb</res-ref-name>
 <res-type>javax.sql.DataSource</res-type>
 <res-auth>Container</res-auth>
</resource-ref>



/* The JSP code */
<%@ page import="java.sql.*, javax.sql.*, javax.naming.*"%>
<%
InitialContext cxt = new InitialContext();
if ( cxt == null ) {
   throw new Exception("Uh oh -- no context!");
}

DataSource ds = (DataSource) cxt.lookup( "java:/comp/env/jdbc/testdb" );
if ( ds == null ) {
   throw new Exception("Data source not found!");
}
try {
    Connection con = ds.getConnection();
} catch (Exception e) {
    out.println(e.getMessage());
}
%>