package cn.itcast.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 cn.itcast.domain.User;
import cn.itcast.service.UserService;

//完成自动登录
public class AutoLoginFilter implements Filter {

	public void destroy() {

	}

	public void doFilter(ServletRequest req, ServletResponse resp,
			FilterChain chain) throws IOException, ServletException {

		// 1.将请求与响应对象强制转换成http协议下的
		HttpServletRequest request = (HttpServletRequest) req;
		HttpServletResponse response = (HttpServletResponse) resp;

		// 2.完成操作--自动登录

		// 判断当前请求路径是否需要进行自动登录.
		String uri = request.getRequestURI();
		String contextPath = request.getContextPath();
		String path = uri.substring(contextPath.length()); // 获取访问的资源路径

		if (path.equals("/demo1/login.jsp") || path.equals("/login")) {
			// 不需要进行自动登录
			chain.doFilter(request, response);
			return;
		} else {
			// 判断用户没有登录
			User u = (User) request.getSession().getAttribute("user");
			if (u == null) {
				// 2.1.从http请求获取cookie
				Cookie[] cs = request.getCookies();
				Cookie cookie = findCookieByName("username", cs);

				if (cookie != null) {
					// 可以进行自动登录
					// 2.2得到cookie中username,password
					String username = cookie.getValue().split(":")[0];
					String password = cookie.getValue().split(":")[1];

					// 2.3.调用service进行登录操作
					UserService service = new UserService();
					try {
						User user = service.login(username, password);

						if (user != null) {
							// 2.4进行登录操作
							request.getSession().setAttribute("user", user);
							chain.doFilter(request, response);
							return;
						} else {
							chain.doFilter(request, response);
							return;
						}

					} catch (SQLException e) {
						e.printStackTrace();
						chain.doFilter(request, response);
						return;
					}

				} else {
					// 没cookie，放行
					chain.doFilter(request, response);
					return;
				}
			} else {
				chain.doFilter(request, response);
				return;
			}

		}
		// 3.放行
		// chain.doFilter(request, response);
	}

	public void init(FilterConfig arg0) throws ServletException {

	}

	public Cookie findCookieByName(String name, Cookie[] cs) {
		if (cs == null || cs.length == 0) {
			return null;
		}

		for (Cookie c : cs) {
			if (name.equals(c.getName())) {
				return c;
			}
		}
		return null;
	}

}

web.xml配置

<!-- 自动登录 -->
	<filter>
		<filter-name>autologin</filter-name>
		<filter-class>cn.itcast.web.filter.AutoLoginFilter</filter-class>
	</filter>
        <filter-mapping>
		<filter-name>autologin</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>