网站页脚,凯里网站建设哪家专业,房产网站设计方案,微网站域名【有道云笔记】二十 4.8 过滤器Filter https://note.youdao.com/s/dSofip3f 一、为什么要使用过滤器 项目开发中#xff0c;经常会用到重复代码的实现。 1、请求每个servlet都要设置编码 2、判断用户是否登录#xff0c;只有登录了才有操作权限。 二、过滤器相关Api int…【有道云笔记】二十 4.8 过滤器Filter https://note.youdao.com/s/dSofip3f 一、为什么要使用过滤器 项目开发中经常会用到重复代码的实现。 1、请求每个servlet都要设置编码 2、判断用户是否登录只有登录了才有操作权限。 二、过滤器相关Api interface Filter 过滤器核心接口 1、init(FilterConfig filterConfig) 初始化方法在服务器启动的时候就执行 2、doFilter(ServletRequest request, ServletResponse response, FilterChain chain) 过滤器拦截的业务逻辑处理 3、destroy() 销毁过滤器实例的时候调用 interface FilterChain 过滤链 doFilter(ServletRequest request, ServletResponse response) 执行下一个过滤器或放行访问servlet 三、案例一用过滤器处理POST请求编码问题 WebFilter(filterName encoding, urlPatterns /*) public class EncodingFilter implements Filter { Override public void init(FilterConfig filterConfig) throws ServletException { } Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println(EncodingFilter.doFilter); HttpServletRequest request (HttpServletRequest) servletRequest; // 这个method是get还是post String method request.getMethod(); // 解决post请求乱码问题 if (post.equalsIgnoreCase(method)) { request.setCharacterEncoding(UTF-8); } filterChain.doFilter(servletRequest, servletResponse); } Override public void destroy() { } } 四、案例二、用过滤器完成登录 // /* 拦截所有的请求 WebFilter(filterName login, urlPatterns /*) public class LoginFilter implements Filter { Override public void init(FilterConfig filterConfig) throws ServletException { Filter.super.init(filterConfig); System.out.println(LoginFilter.init); } // ServletRequest servletRequest new HttpServletRequest() Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println(LoginFilter.doFilter); HttpServletRequest request (HttpServletRequest) servletRequest; HttpServletResponse response (HttpServletResponse) servletResponse; String servletPath request.getServletPath(); System.out.println(servletPath: servletPath); String method request.getParameter(method); //这是请求是要去完成登录的不需要执行后面验证是否登录的流程 if (servletPath.endsWith(.jpg) || servletPath.endsWith(.png) || servletPath.endsWith(.js) || servletPath.endsWith(.css) || servletPath.equals(/login.jsp) || servletPath.equals(/user) login.equals(method)) { filterChain.doFilter(servletRequest, servletResponse); return; } HttpSession session request.getSession(); User user (User) session.getAttribute(user); if (user null) { response.sendRedirect(/login.jsp); return; } //加了这句话代表方行继续往后执行 //如果还有filter就访问后面filter没有filter就可以访问后台资源 filterChain.doFilter(servletRequest, servletResponse); } Override public void destroy() { Filter.super.destroy(); System.out.println(LoginFilter.destroy); } } 五、web.xml配置servlet和过滤器 servlet和filter除了用注解方式配置还可以使用xml的方式配置 WEB-INF/web.xml是Web项目的核心配置文件 ?xml version1.0 encodingUTF-8? web-app xmlnshttp://xmlns.jcp.org/xml/ns/javaee xmlns:xsihttp://www.w3.org/2001/XMLSchema-instance xsi:schemaLocationhttp://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd version4.0 !-- WebServlet(/student) public class StudentServlet extends HttpServlet { } -- servlet servlet-namestudentServlet/servlet-name servlet-classcom.situ.web.controller.StudentServlet/servlet-class /servlet servlet-mapping servlet-namestudentServlet/servlet-name url-pattern/student/url-pattern /servlet-mapping filter filter-nameencoding/filter-name filter-classcom.situ.web.filter.EncodingFilter/filter-class /filter filter-mapping filter-nameencoding/filter-name url-pattern/*/url-pattern /filter-mapping filter filter-namelogin/filter-name filter-classcom.situ.web.filter.LoginFilter/filter-class /filter filter-mapping filter-namelogin/filter-name url-pattern/*/url-pattern /filter-mapping /web-app