您需要实现ServletContextListner接口，并在其中启动要在tomcat启动时执行的代码。

这是有关它的简短描述。

ServletContextListner在javax.servlet包中。

这是有关如何执行的简短代码。

public class MyServletContextListener implements ServletContextListener {

  @Override
  public void contextDestroyed(ServletContextEvent arg0) {
    //Notification that the servlet context is about to be shut down.   
  }

  @Override
  public void contextInitialized(ServletContextEvent arg0) {
    // do all the tasks that you need to perform just after the server starts

    //Notification that the web application initialization process is starting
  }

}

并且您需要在部署描述符web.xml中对其进行配置

<listener>
    <listener-class>
        mypackage.MyServletContextListener
    </listener-class>
</listener>