Filter实现自动登录

比眉伴天荒 2022-04-04 05:20 283阅读 0赞

filter的简介

filter是对客户端访问资源的过滤，符合条件放行，不符合条件不放行，并且可以对目 标资源访问前后进行逻辑处理

步骤：

思路： 前台有一个 <input type="checkbox" name="autoLogin" value="autoLogin"> 自动登录，当判断选中的时候，把username和password存到cookie中，当你关闭浏览器，再次打开的时候，先经过filter，判断cookie中是否有username和password，如果有，取出来，从数据库中查到user，存到session中，chain.doFilter(request, response);放行，就达到自动登陆的目的。

1.  编写一个过滤器的类实现Filter接口
2.  实现接口中尚未实现的方法(着重实现doFilter方法)
3.  在web.xml中进行配置(主要是配置要对哪些资源进行过滤)

前台是一个form表单login.jsp

success.jsp  成功就可以取出session中的user

<c:if test="${empty user }">
    				<li><a href="login.jsp">登录</a></li>
    				<li><a href="register.jsp">注册</a></li>
    			</c:if>
    			<c:if test="${!empty user }">
    				<li>欢迎您,${user.username }</li>
    				<li><a href="#">退出</a></li>
    			</c:if>

1. 编写servlet

request.setCharacterEncoding("UTF-8");
    		String username = request.getParameter("username");
    		String password = request.getParameter("password");
    		HttpSession session = request.getSession();
    		
    		loginService loginService = new loginService();
    		User user = null;
    		try {
                    //从数据库中根据username和password查询user
    			user = loginService.findUser(username,password);
    		} catch (SQLException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		if(user!=null) {
    			String autoLogin = request.getParameter("autoLogin");
    			if(autoLogin!=null) {
                        //对username进行编码（如果是中文）
    				String username_code = URLEncoder.encode(username, "UTF-8");
                        //username和password  cookie
    				Cookie cookie_username = new Cookie("username1",username_code);
    				Cookie cookie_password = new Cookie("password1",user.getPassword());
                        //设置存活时间
    				cookie_username.setMaxAge(60*60);
    				cookie_password.setMaxAge(60*60);
                        //设置访问路径
    				cookie_username.setPath(request.getContextPath());
    				cookie_password.setPath(request.getContextPath());
    				response.addCookie(cookie_username);
    				response.addCookie(cookie_password);
    			}
                    //存在session中
    			session.setAttribute("user", user);
    			response.sendRedirect(request.getContextPath());
    		}else {
    			System.out.println(username);
    			request.setAttribute("loginInfo", "用户名或密码错误");
    			request.getRequestDispatcher("/login.jsp").forward(request, response);
    		}

2.过滤器的类实现Filter接口

package web.filter;
    
    import java.io.IOException;
    import java.sql.SQLException;
    
    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.http.Cookie;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    
    import com.ithiema.domain.User;
    import com.ithiema.service.loginService;
    
    public class AutoLogin implements Filter{
    
    	@Override
    	public void destroy() {
    		// TODO Auto-generated method stub
    		
    	}
    
    	@Override
    	public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
    			throws IOException, ServletException {
    		
    		String cookie_username = null;
    		String cookie_password = null;
    		
    		HttpServletRequest request = (HttpServletRequest) req;
    		HttpServletResponse response = (HttpServletResponse) res;
    		HttpSession session = request.getSession();
    		Cookie[] cookies = request.getCookies();
    		if(cookies!=null) {
    			for(Cookie cookie:cookies) {
    				if("username1".equals(cookie.getName())) {
    					cookie_username = cookie.getValue();
    				}
    				if("password1".equals(cookie.getName())) {
    					cookie_password = cookie.getValue();
    				}
    			}
    		}
    		if(cookie_username!=null&&cookie_password!=null) {
    			loginService loginService = new loginService();
    			User user = null;
    			try {
                                //取出username和password  从数据库中查user
    				user = loginService.findUser(cookie_username, cookie_password);
    			} catch (SQLException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    			session.setAttribute("user", user);
    		}
                    //放行
    		chain.doFilter(request, response);
    	}
    
    	@Override
    	public void init(FilterConfig arg0) throws ServletException {
    		// TODO Auto-generated method stub
    		
    	}
    
    }

3.web.xml中添加这个

<filter>
        <filter-name>AutoLoginFilter</filter-name>
        <filter-class>web.filter.AutoLogin</filter-class>
      </filter>
      <filter-mapping>
        <filter-name>AutoLoginFilter</filter-name>
        <url-pattern>/*</url-pattern>
      </filter-mapping>