java使用Filter实现自动登录的方法

本文实例为大家分享了java实现自动登录的具体代码，供大家参考，具体内容如下

• 当你勾选（记住登录状态），用cookie保存用户名和密码。不勾选，cookie失效。

• 所有的页面都要经过autoLoginFilter.java 的过滤器，在这类中，必须要判断cookies不为null，获得所有的cookie，得到name为user的cookie，进行用户名和密码的验证，如果不为null，则将user存入session。

• 在LoginServlet.java中，获得username和password参数，进行dao验证，如果不为空，放入seesion中，进行页面跳转。

• 创建cookie对象。setpath("/"),表示本应用下的所有路径都能访问此cookie。

• 对于已经正确登录的用户，再次访问其他页面必定会再次经过autoLoginFilter，这时，判断当前session中的user是否为null，不为null，直接通过。

• 对于**login.jsp的有关页面，不需要经过autoLoginFilter。
  

package com.learning.web.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.learning.domain.User;
import com.learning.service.UserService;

@WebServlet("/servlet/loginServlet")
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 String username = request.getParameter("username");
 String password = request.getParameter("password");
 String autologin = request.getParameter("autologin");

UserService userService=new UserService();
 User user = userService.findUser(username, password);
 //user不为null，则登录成功
 if (user!=null) {
 //创建cookie来保存用户信息
 Cookie cookie=new Cookie("user", user.getUsername()+"&"+user.getPassword());
 cookie.setPath("/");
 //autologin不为null，则记住了登录状态
 if (autologin!=null) {
  cookie.setMaxAge(1*60*60*24);//一天的有效时间
 }
 else {
  cookie.setMaxAge(0);
 }
 response.addCookie(cookie);
 request.getSession().setAttribute("user", user);
 request.getRequestDispatcher("/home.jsp").forward(request, response);
 }else {
 response.sendRedirect(request.getContextPath()+"/homeLogin.jsp");
 }

}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}

}

package com.learning.web.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.jstl.core.Config;

import com.learning.domain.User;
import com.learning.service.UserService;

@WebFilter(urlPatterns="/*",initParams={@WebInitParam(name="autologin",value="login"),@WebInitParam(name="",value="")})
public class AutoFilter implements Filter{

private FilterConfig filterConfig;
@Override
public void destroy() {
}

@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
 throws IOException, ServletException {
// 转换对象
HttpServletRequest httpServletRequest = (HttpServletRequest) request;
HttpServletResponse httpServletResponse = (HttpServletResponse) response;
// 获得访问的路径
String uri = httpServletRequest.getRequestURI();
String contextPath = httpServletRequest.getContextPath();
uri = uri.substring(contextPath.length() + 1);
// 获得初始化参数
String login = filterConfig.getInitParameter("autologin");
System.out.println("直接通行的路径："+login);
// 不包含"login"的路径就要进行过滤 （xxxlogin.jsp 不需要自动登录）
if (!uri.contains(login)) {
 HttpSession session = httpServletRequest.getSession();
 User u = (User) session.getAttribute("user");
 if (u != null) {
 System.out.println("session不为null");
 chain.doFilter(request, response);
 } else {

// 处理业务逻辑
 // 1.获得cookie 得到User的信息

String username = "";
 String password = "";
 UserService userService = new UserService();
 Cookie[] cookies = httpServletRequest.getCookies();
 for (int i = 0;cookies!=null&& i < cookies.length; i++) {
  if ("user".equals(cookies[i].getName())) {
  String string = cookies[i].getValue();
  String[] values = string.split("&");
  username = values[0];
  password = values[1];
  User user = userService.findUser(username, password);

// 不为空则放入session
  if (user != null) {
   System.out.println("自动登录了");
   httpServletRequest.getSession().setAttribute("user", user);
  }
  }
 }
 }
}
// 2.放行
chain.doFilter(request, response);
}

@Override
public void init(FilterConfig filterConfig) throws ServletException {

this.filterConfig=filterConfig;

}

}