<?xml version="1.0" encoding="UTF-8"?>

<Resources name="jdbc/murach" auth="Containter"
    driverClassName="com.mysql.jdbc.Driver"
    url="jdbc:mysql://localhost:3306/murach"
    username="root" password="root"
    maxActive="100" maxIdle="30" maxWait="10000"
    logAbandoned="true" removeAbandoned="true"
    removeAbandonedTimeout="60" type="javax.sql.DataSource" />

 <ResourceLink name="jdbc/murach"
         global="jdbc/mydb"
          type="javax.sql.DataSource" />

package lars.data;

import java.sql.Connection;
import java.sql.SQLException;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;


public class ConnectionPool {
    private static ConnectionPool pool = null;
    private static DataSource dataSource = null;

    private ConnectionPool() {
        try {
            InitialContext ic = new InitialContext();
            dataSource = (DataSource) ic.lookup("java:/comp/env/jdbc/murach");
            System.out.print(dataSource);
        } catch (NamingException e) {
            System.out.println(e);
        }
    }

    public static synchronized ConnectionPool getInstance() {
        if (pool == null) {
            pool = new ConnectionPool();
        }
        return pool;
    }

    public Connection getConnection() {
        try {
            return dataSource.getConnection();
        } catch (SQLException e) {
            System.out.println(e);
            return null;
        }
    }

    public void freeConnection(Connection c) {
        try {
            c.close();
        } catch (SQLException e) {
            System.out.println(e);
        }
    }
}

<ResourceLink name="jdbc/murach"
         global="jdbc/murach"
          type="javax.sql.DataSource" />

<Resource name="jdbc/murach" ... />