监听器常见应用

窗口的关闭
public class Test {
    public static void main(String[] args) {
        Frame frame = new Frame("元宵节快乐");//新建一个窗体
        Panel panel = new Panel(null);//面板
        frame.setLayout(null);//设置窗体的布局

        frame.setBounds(300,300,500,500);
        frame.setBackground(new Color(0,0,255)); //设置背景颜色

        panel.setBounds(50,50,300,300);
        panel.setBackground(new Color(0,255,0)); //设置背景颜色

        frame.add(panel);
        frame.setVisible(true);

        //监听事件，监听关闭事件
        frame.addWindowListener(new WindowListener() {
            @Override
            public void windowOpened(WindowEvent e) {
                System.out.println("打开");
            }

            @Override
            public void windowClosing(WindowEvent e) {
                System.out.println("关闭ing");
                System.exit(0);

            }

            @Override
            public void windowClosed(WindowEvent e) {
                System.out.println("关闭");

            }

            @Override
            public void windowIconified(WindowEvent e) {

            }

            @Override
            public void windowDeiconified(WindowEvent e) {

            }

            @Override
            public void windowActivated(WindowEvent e) {
                System.out.println("激活");
            }

            @Override
            public void windowDeactivated(WindowEvent e) {
                System.out.println("未激活");
            }
        });


    }
}


用户登录之后才能进入页面！ 用户注销以后就不能进入主页了！
1、用户登录以后，向Session中放入用户的数据
2、进入主页的时候要判断用户是否已经登录。   要求：在过滤器中实现

    HttpServletRequest request = (HttpServletRequest) req;
    HttpServletResponse response = (HttpServletResponse) resp;

    if (request.getSession().getAttribute(Constant.USER_SESSION)==null){
        response.sendRedirect("/error.jsp");
    }


    filterChain.doFilter(request,response);