练习一：session 实现登录注销
package com.dzq.session.logout;
import java.util.*;
public class UserDao {
/**
* 存储用户信息，代替数据库
*/
private UserDao(){
}
private static Map<String, String> map=new HashMap<String, String>();
static{
map.put("张三丰", "111");
map.put("Adele", "111");
map.put("小杜", "111");
}
public static boolean valiNP(String username,String password){
return map.containsKey(username)&&map.get(username).equals(password);
}
}
我。。。。。。。。。。。。。。。。。。是。。。。。。。。。。。。分。。。。。。。。。。割。。。。。。。。。。线。。。。。。。。。。。。。。
package com.dzq.session.logout;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
/**
* 实现登录的servlet，登陆后重定向到主页index。jsp
*/
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
String username=request.getParameter("username");
String password=request.getParameter("password");
if(UserDao.valiNP(username, password)){
request.getSession().setAttribute("user", username);
response.sendRedirect(request.getContextPath()+"/logout/index.jsp");
}else{
response.getWriter().write("用户名或者密码错误");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
我。。。。。。。。。。。。。。。。是。。。。。。。。。。。。分。。。。。。。。。。割。。。。。。。。。。线。。。。。。。。。。。。
package com.dzq.session.logout;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/LogoutServlet")
public class LogoutServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* 注销登录的servlet ，销毁session ，重定向到index。jsp
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
if(request.getSession(false)!=null&&request.getSession().getAttribute("user")!=null){
request.getSession().invalidate();
}
response.sendRedirect(request.getContextPath()+"/logout/index.jsp");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
我。。。。。。。。。。。。。。是。。。。。。。。。。。。分。。。。。。。。。。割。。。。。。。。。。线。。。。。。。。。。。
我 的 下 面 是 jsp 页 面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- 主页index.jsp -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>我的网站</h1><hr>
<%
String user=(String)session.getAttribute("user");
%>
<%
if(user==null||"".equals(user)){
%>
欢迎光临，游客....
<a href="login.jsp">登录</a>
<a href="#">注册</a>
<%
}else{
%>
欢迎回来，<%=user %>
<a href="${pageContext.request.contextPath }/LogoutServlet">注销</a>
<%
}
%>
</body>
</html>
我。。。。。。。。。。。。。。是。。。。。。。。。。。。分。。。。。。。。。。割。。。。。。。。。。线。。。。。。。。。。。。
我 的 下 面 还 是 jsp 页 面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- 登录页面 -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>我的网站</h1><hr>
<form action="${pageContext.request.contextPath }/LoginServlet" method="post">
用户名：<input type="text" name="username" />
密码：<input type="password" name="password"/>
<input type="submit" value="登录"/>
</form>
</body>
</html>
练习二：session 实现防止表单重复提交:
package com.dzq.session.resubmit;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/ResubServlet")
public class ResubServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* 获取session 防止重复提交
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
try {
Thread.sleep(4*1000);
} catch (Exception e) {
e.printStackTrace();
}
String username=request.getParameter("username");
String valinum=request.getParameter("valinum");
String valinum2=(String) request.getSession().getAttribute("valinum");
if(valinum2!=null&& !"".equals(valinum2)&&valinum.equals(valinum2)){
request.getSession().removeAttribute("valinum");
System.out.println("向数据库中注册一次"+username);
}else{
response.getWriter().write("web不要重复提交");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
我。。。。。。。。。。。。。。是。。。。。。。。分。。。。。。。。割。。。。。。。。。。线。。。。。。。。。。。。
我 的 下 面 是 jsp 页 面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<!-- <script type="text/javascript">
var isNotSub=true;
function canSub() {
if(isNotSub){
isNotSub=false;
return true;
}else{
alert("请不要重复提交");
return false;
}
}
</script> -->
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
Random r=new Random();
int valinum=r.nextInt();
session.setAttribute("valinum", valinum+"");
%>
<form action="${pageContext.request.contextPath }/ResubServlet" method="post" onsubmit="return canSub()">
<input type="text" name="username"/>
<input type="hidden" name="valinum" value="<%=valinum%>"/>
<input type="submit" value="提交"/>
</form>
</body>
</html>