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; }}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。