package k.filter;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class StartSystemListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        //1.将项目上下文路径(request.getContextPath())放置到application域中.
        ServletContext application = sce.getServletContext();
        application.setAttribute("APP_PATH", application.getContextPath());
        System.err.println("=============Servlet容器创建成功 APP_PATH 被放到ServletContext作用域============= " + application.getContextPath());
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {

    }
}

    <listener>
        <display-name>StartSystemListener</display-name>
        <listener-class>k.filter.StartSystemListener</listener-class>
    </listener>

<h1>登录页面</h1>
<form action="${APP_PATH}/login.do" method="post">
    账号：<input type="text" name="userName" value="11哈哈"> <br>
    密码： <input type="password" name="password" value="1"> <br>
    <input type="submit" value="submit"> <br>
</form>