会话技术Session

1.Session的概念

Session是依赖于Cookie的，
每次请求时，会将特殊标识带到服务器端，根据这个标识来找到对应的内存空间，从而实现数据共享!是Servlet规范中四大域对象之一的会话域对象。
作用:是Servlet规范中四大域对象之一的会话域对象。可以实现数据共享

2.Session设置共享数据

//Session的基本使用
@WebServlet("/ServletDemo1")
public class ServletDemo1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//设置请求字符编码,防止乱码req.setCharacterEncoding("utf-8");//设置浏览器响应编码[html类型的文本,字符集为utf-8]resp.setContentType("text/html;charset=utf-8");//1.获取请求的用户名String username = req.getParameter("username");//2.获取HttpSession的对象HttpSession session = req.getSession(true);//默认为true,表示没有session则自动创建//[验证是否为同一Session]System.out.println(session);System.out.println(session.getId());//3.将用户名信息添加到共享数据中session.setAttribute("username",username);//2.解决Cookie禁用方法2：重写url"<a href='"+resp.encodeURL("http://localhost:8080/Session/ServletDemo3")+"'>go servletDemo1</a>"// resp.getWriter().write("<a href='"+resp.encodeURL("http://localhost:8080/Session/ServletDemo3")+"'>go servletDemoO</a>");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

3.Session获取共享数据

//Session获取共享数据[同一个session]
@WebServlet("/ServletDemo2")
public class ServletDemo2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//设置浏览器响应编码[html类型的文本,字符集为utf-8]resp.setContentType("text/html;charset=utf-8");//1.获取HttpSession对象HttpSession session = req.getSession();//[验证是否为同一Session]System.out.println(session);System.out.println(session.getId());//2.获取共享数据String username = (String) session.getAttribute("username");//3.将响应数据给浏览器resp.getWriter().write(username);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

4.Cookie的禁用解决方法

//Cookie的禁用
@WebServlet("/ServletDemo3")
public class ServletDemo3 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//1.解决方法1：提示HttpSession session = req.getSession(false);System.out.println(session);if (session==null){resp.setContentType("text/html;charset=utf-8");resp.getWriter().write("为了不影响使用，请不要禁用浏览器的Cookie");}//2.解决方法2：重写url"<a 【需到第一个界面重写】href='"+resp.encodeURL("http://localhost:8080/Session/ServletDemo3")+"'>go servletDemo1</a>"// resp.getWriter().write("<a href='"+resp.encodeURL("http://localhost:8080/Session/ServletDemo3")+"'>go servletDemoO</a>");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}