cookie、session和java过滤器结合实现登陆程序
cookie、session和过滤器通常都是用在web应用中,cookie和session用来保存一定的数据,过滤器Filter则是在浏览器发出请求之后,而后台执行特定的请求之前发生一定的作用。之所以把这三个放一起,是因为有很多时候都会是把他们结合在一起使用,例如有些登陆程序。
cookie是浏览器的机制,session是服务器的机制,但是实际上cookie也是由服务器生成的,之后返回给浏览器的,并不是浏览器本身生成。当浏览器发送某个请求时,如果拥有有效的cookie则会把这个cookie带在一起。
之所有会有cookie的使用,是因为http协议原本是无状态协议,也就是说通过http协议本身,服务器不能判断浏览器是否之前访问过。
Filter和servlet的写法相似,编写相关代码的时候需要实现Filter接口并重写相关的方法,通常更改较多的是doFilter方法。Filter代码写好以后如果需要发生效用,需要像配置servlet一样在web.xml中进行一定的配置。
以下是一个简单的结合cookie、session、Servlet和Filter的登陆示例代码:
定义一个用户实体类,充当数据库数据,这里使用单例模式,保证只存在一个实例对象:
packagemodels; /** *用户信息实体类 * *@authortuzongxun123 * */ publicclassUserModel{ privateStringuserName; privateStringpassword; //单例模式,保证只有一个用户对象实例 publicstaticUserModelgetInstance(){ UserModeluser=newUserModel("zhangsan","123456"); returnuser; } privateUserModel(StringuserName,Stringpasword){ this.userName=userName; this.password=pasword; } publicStringgetUserName(){ returnuserName; } publicStringgetPassword(){ returnpassword; } }
用户登陆输入信息index.jsp界面,在form表单的action中使用jsp的特性获得项目路径:
<%@pagelanguage="java"import="java.util.*"contentType="text/html;charset=utf-8" pageEncoding="utf-8"%> <!DOCTYPEhtmlPUBLIC"-//W3C//DTDHTML4.01Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <metahttp-equiv="Content-Type"content="text/html;charset=utf-8"> <title>cookieAndFilterTest</title> </head> <body> <formaction="<%=request.getContextPath()%>/loginServlet"method="post"> userName:<inputtype="text"name="userName"/></br> password:<inputtype="password"name="password"/></br> <inputtype="submit"value="login"/> </form> </body> </html>
对应的后台servlet:
packageservletTest; importjava.io.IOException; importjavax.servlet.ServletException; importjavax.servlet.http.Cookie; importjavax.servlet.http.HttpServlet; importjavax.servlet.http.HttpServletRequest; importjavax.servlet.http.HttpServletResponse; importjavax.servlet.http.HttpSession; importmodels.UserModel; publicclassLoginServletextendsHttpServlet{ @Override protectedvoiddoGet(HttpServletRequestreq,HttpServletResponseresp) throwsServletException,IOException{ this.doPost(req,resp); } @Override protectedvoiddoPost(HttpServletRequestreq,HttpServletResponseresp) throwsServletException,IOException{ StringuserName=req.getParameter("userName"); Stringpassword=req.getParameter("password"); //模拟数据库数据 UserModeluser=UserModel.getInstance(); StringdbUserName=user.getUserName(); StringdbPassword=user.getPassword(); if(dbUserName.equals(userName)&&dbPassword.equals(password)){ //用户名和密码都匹配,证明登陆成功,设置session和cookie HttpSessionsession=req.getSession(); session.setAttribute("userName",userName); session.setAttribute("password",password); Cookiecookie=newCookie("userName",userName); Cookiecookie2=newCookie("password",password); //设置cookie的存储时长 cookie.setMaxAge(60); cookie2.setMaxAge(60); //把cookie发送给浏览器 resp.addCookie(cookie); resp.addCookie(cookie2); //转发请求到用户列表 req.getRequestDispatcher("/userList").forward(req,resp); }else{ //转发请求到登陆页面 req.getRequestDispatcher("index.jsp").forward(req,resp); } ; } }
上边登陆后跳转的请求:
packageservletTest; importjava.io.IOException; importjavax.servlet.ServletException; importjavax.servlet.http.HttpServlet; importjavax.servlet.http.HttpServletRequest; importjavax.servlet.http.HttpServletResponse; importmodels.UserModel; publicclassUserListServletextendsHttpServlet{ @Override protectedvoiddoGet(HttpServletRequestreq,HttpServletResponseresp) throwsServletException,IOException{ this.doPost(req,resp); } @Override protectedvoiddoPost(HttpServletRequestreq,HttpServletResponseresp) throwsServletException,IOException{ UserModeluser=UserModel.getInstance(); //在浏览器中打印出用户列表书数据 resp.getWriter().write( "userName:"+user.getUserName()+","+"password:" +user.getPassword()); } }
项目web.xml配置:
<?xmlversion="1.0"encoding="UTF-8"?> <web-appxmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee"xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaeehttp://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID"version="2.5"> <!--访问时的项目名称--> <display-name>cookieAndFilterTest</display-name> <!--servlet配置--> <servlet> <servlet-name>login</servlet-name> <servlet-class>servletTest.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>login</servlet-name> <url-pattern>/loginServlet</url-pattern> </servlet-mapping> <servlet> <servlet-name>userList</servlet-name> <servlet-class>servletTest.UserListServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>userList</servlet-name> <url-pattern>/userList</url-pattern> </servlet-mapping> <!--过滤器设置,浏览其发送请求后首先会走这里--> <filter> <filter-name>loginFilter</filter-name> <filter-class>filterTest.FilterTest</filter-class> </filter> <filter-mapping> <filter-name>loginFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!--输入项目名访问的默认页面--> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
java过滤器代码:
packagefilterTest; importjava.io.IOException; importjavax.servlet.Filter; importjavax.servlet.FilterChain; importjavax.servlet.FilterConfig; importjavax.servlet.ServletException; importjavax.servlet.ServletRequest; importjavax.servlet.ServletResponse; importjavax.servlet.http.Cookie; importjavax.servlet.http.HttpServletRequest; importjavax.servlet.http.HttpServletResponse; importmodels.UserModel; publicclassFilterTestimplementsFilter{ @Override publicvoiddestroy(){ } @Override publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse, FilterChainchain)throwsIOException,ServletException{ //登陆请求、初始请求直接放行 HttpServletRequestreq=(HttpServletRequest)request; HttpServletResponseresp=(HttpServletResponse)response; Stringuri=req.getRequestURI(); if("/cookieAndFilterTest/loginServlet".equals(uri) ||"/cookieAndFilterTest/".equals(uri)){ //放行 chain.doFilter(request,response); return; } //不是登陆请求的话,判断是否有cookie Cookie[]cookies=req.getCookies(); if(cookies!=null&&cookies.length>0){ StringuserName=null; Stringpassword=null; //判断cookie中的用户名和密码是否和数据库中的一致,如果一致则放行,否则转发请求到登陆页面 for(Cookiecookie:cookies){ if("userName".equals(cookie.getName())){ userName=cookie.getValue(); } if("password".equals(cookie.getName())){ password=cookie.getValue(); } } UserModeluser=UserModel.getInstance(); if(user.getUserName().equals(userName) &&user.getPassword().equals(password)){ chain.doFilter(request,response); return; }else{ //重定向到登陆界面 req.getRequestDispatcher("/index.jsp").forward(req,resp); return; } }else{ req.getRequestDispatcher("/index.jsp").forward(req,resp); return; } } @Override publicvoidinit(FilterConfigarg0)throwsServletException{ } }
以上就是本文的全部内容,希望对大家学习java程序设计有所帮助。