<Resource
    name="jdbc/mysql"
    auth="Container"
    type="javax.sql.DataSource"
    maxActive="100"
    maxIdle="30"
    maxWait="10000"
    driverClassName="com.mysql.jdbc.Driver"
    url="jdbc:mysql://服务器地址:端口号/数据库名称"
    username="数据库用户名"
    password="数据库密码"
/>

public class test {

    Connection connection = null;

    public Connection tomcatGetConnection() {
        try {
            Context context = new InitialContext();
            DataSource dataSource = (DataSource) context.lookup("java:comp/env/jdbc/mysql");
            connection = dataSource.getConnection();
        } catch (NamingException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }
}