web学习03
获取表单提供的数据
html form表单
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
String name = request.getParameter("username");
String password = request.getParameter("password");
String sex = request.getParameter("sex");
String[] hobbys = request.getParameterValues("hobby");
String city = request.getParameter("city");
System.out.println(name);
System.out.println(password);
System.out.println(sex);
for (String string : hobbys) {
System.out.println(string);
}
System.out.println(city);把请求中的参数放到map中
Map map = request.getParameterMap();
for (String string : map.keySet()) {
System.out.println(string);
for (String string2 :map.get(string)) {
System.out.println(string2);
}
} Enumeration names = request.getParameterNames();
while (names.hasMoreElements()) {
System.out.println(names.nextElement());
} 将表单提交的数据封装到user对象中
String name = request.getParameter("username");
String password = request.getParameter("password");
String sex = request.getParameter("sex");
String[] hobbys = request.getParameterValues("hobby");
String city = request.getParameter("city");
User user=new User(name,password,sex,hobbys,city);请求转发
一次请求 并且响应到网页的是转发后的响应结果
请求重定向
两次请求 超出了request域的作用范围 不能使用request传值
请求包含
几次请求? 一次请求(说明可以用request域传值)
最终响应到网页的内容是什么?
两个servlet的响应结果会一起返回给浏览器
Request域对象
内部维护了一个map集合 添加获取删除值
作用范围:只对一次请求有效
请求转发 通过请求对象获取请求转发器
RequestDispatcher dispatcher = request.getRequestDispatcher("/demo03");
dispatcher.forward(request, response);请求重定向 参数是重定向的地址
response.sendRedirect("/sh-web-03/demo03");请求包含 获取请求转发器
RequestDispatcher dispatcher = request.getRequestDispatcher("/demo03");
dispatcher.include(request, response);会话技术 客户端与服务端之间的交互
什么是会话?相当于打电话
访问网页时只要浏览器不关闭 点击多次连接也叫一次会话
关闭浏览器 结束会话
1.客户端技术 Cookie 保存客户端(浏览器中) 是一个文件
每个站点(网站)可以保存20个cookie
每个浏览器可以保存300个cookie
每个cookie可以保存4kb的数据
cookie默认的存活时间 :一次会话
关闭浏览器 cookie被清除 默认保存在浏览器的内存中
可以设置cookie的存活时间 1年
浏览器会将cookie保存到硬盘中(保存到文件中)
注意:cookie不能保存中文
设置cookie存活时间
setMaxAge(时间 以秒为单位)
正值 值是多少 浏览器保存多少秒
负值 浏览器不会存储cookie到硬盘当中
当浏览器关闭 会话结束 cookie被删除
0时 cookie被删除
2.服务端技术 HttpSession
session保存在服务端
需求: 显示上一次(最后一次)的登录时间
关闭浏览器之后再访问还能显示
1.第一下访问servlet时 将时间保存到cookie中
在响应会浏览器 让浏览器存储起来
下一次访问时通过request请求获取之前保存的cookie
显示之前储存的额时间
public class Demo04 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
Cookie[] cookies = request.getCookies();
if (cookies!=null) {
for (Cookie cookie : cookies) {
if (cookie.getName().equals("lastTime")) {
String value = cookie.getValue();
long time = Long .parseLong(value);
Date date=new Date(time);
SimpleDateFormat dateFormat=
new SimpleDateFormat("yyyy:MM:dd:HH:mm:ss");
String lastTime = dateFormat.format(date);
System.out.println("上次的登录时间"+lastTime);
response.getWriter().write("上次的登录时间"+lastTime);
}
}
}
Cookie cookie=new Cookie("lastTime", System.currentTimeMillis()+"");
cookie.setPath("/");
cookie.setMaxAge(60*5);
response.addCookie(cookie);
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
public class Demo05 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
Cookie[] cookies = request.getCookies();
if (cookies!=null) {
for (Cookie cookie : cookies) {
if (cookie.getName().equals("lastTime")) {
String value = cookie.getValue();
long time = Long .parseLong(value);
Date date=new Date(time);
SimpleDateFormat dateFormat=
new SimpleDateFormat("yyyy:MM:dd:HH:mm:ss");
String lastTime = dateFormat.format(date);
System.out.println("上次的登录时间"+lastTime);
response.getWriter().write("上次的登录时间"+lastTime);
}
}
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
登录后下次打开浏览器 还能记录用户名
public class Demo06 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
String username="";
String remember="";
Cookie[] cookies = request.getCookies();
if (cookies!=null) {
System.out.println("123");
for (Cookie cookie : cookies) {
if (cookie.getName().equals("username")) {
username=cookie.getValue();
remember="checked='checked'";
}
}
}
System.out.println(username);
response.getWriter().write("");
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}public class Demo07 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
String username = request.getParameter("username");
String password = request.getParameter("password");
String remember = request.getParameter("remember");
Cookie cookie=new Cookie("username", username);
cookie.setPath("/sh-web-03/servlet");
if (username.equals("wanglong")&&password.equals("123")) {
if (remember!=null) {
cookie.setMaxAge(Integer.MAX_VALUE);
}else {
cookie.setMaxAge(0);
}
response.getWriter().write("登录成功");
response.addCookie(cookie);
}else {
response.getWriter().write("登录失败");
response.setHeader("refresh", "3;url=/sh-web-03/servlet/demo06");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}