Error in connecting to the mySQL database in TOMCAT using more than one PC (database connection pooling)

how do i implement connection pooling with tomcat5.5?

i have updated context.xml

<Context path="/HTHL" docBase="webapps/HTHL"  
          debug="5" reloadable="true" crossContext="true" >
    <!-- Default set of monitored resources -->
    <WatchedResource>WEB-INF/web.xml</WatchedResource> <Resource name="jdbc/HTHLogDB" auth="Container" type="javax.sql.DataSource" 
    maxActive="10" maxIdle="15" maxWait="10000"  
    removeAbandoned="true" removeAbandonedTimeout="60" logAbandoned="true"       
    username="msos" password="passw0rd" driverClassName="com.mysql.jdbc.Driver"

    url="jdbc:mysql://10.9.58.8:3306/alcs_htht"/> </Context>

and web.xml

<web-app>
      <description>HTHLogweb</description>
      <resource-ref>
            <description>HTHLog DB Connection</description>
            <res-ref-name>jdbc/HTHLogDB</res-ref-name>
            <res-type>javax.sql.DataSource</res-type>
            <res-auth>Container</res-auth>
       </resource-ref>
      <session-config>
        <session-timeout>35</session-timeout>
      </session-config>
      <mime-mapping>
        <extension>html</extension>
        <mime-type>text/html</mime-type>
      </mime-mapping>
      <mime-mapping>
        <extension>txt</extension>
        <mime-type>text/plain</mime-type>
      </mime-mapping>
        <welcome-file-list>
        <welcome-file>/login.jsp</welcome-file>
      </welcome-file-list>
    </web-app>

and connected with the following code

public static final String strDataSource = "java:comp/env/jdbc/HTHLogDB"; 
ic = new InitialContext();
ds = (DataSource)ic.lookup(strDataSource);
con = ds.getConnection();

I was able to successfully connect using one PC. But when I use another PC to access the same application/database, I get a java.lang.NullPointer Exception.

Can you help me?

I tried using DriverManager.getConnection, and I can work with two or more PCs, however this will not be efficient, as it will create one-to-one connection. (16PCs - 16 connection) Need your help badly. Thanks!