Filter: 过滤器、装饰者设计模式解决乱码、自动登录

一。Filter: 过滤器：

步骤: 1.自定义类, 实现Filter接口 2.重点实现doFilter方法 3.注册Filter @WebFilter web.xml-配置] 4.doFilter中, 直接响应, 要么放行 chain.doFilter 5.测试: 发送的是Servlet请求

多个过滤器顺序: web.xml文件中的标签顺序

FilterChain: 过滤器链, 由filter-mapping将过滤器连接串起来的 doFilter() -> 执行下一个过滤器, 递归

Filter生命周期: 服务器启动创建 服务器关闭销毁

FilterConfig 《init-param》 《param-name》driver《/param-name》 《param-value》com.mysql.cj.jdbc.Driver《/param-value》 《/init-param》 config.getInitParameter(“driver”); ServletConfig

public class FilterC implements Filter { public void destroy() { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException { System.out.println("MyfilterC"); chain.doFilter(request, response); } public void init(FilterConfig config) throws ServletException { String qqai = config.getInitParameter("qqai");//获得xml文件中init-param的初始化参数 System.out.println(qqai); } } @WebServlet("/requstServlet") public class requstServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("servelet进入"); } ------------------------------------------------------ <filter> <filter-name>FilterC</filter-name> <filter-class> filter.FilterC</filter-class> <!-- init-param :可被FilterConfig获得的的初始化参数--> <init-param> <param-name>qqai</param-name> <param-value>com.qqai</param-value> </init-param> </filter> <!--过滤器运行的先后顺序，谁的filter-mapping写在前面谁先--> <filter-mapping> <filter-name>FilterC</filter-name> <url-pattern>/requstServlet</url-pattern> </filter-mapping>

二。装饰者设计模式解决乱码

Get请求默认字符集: tomcat字符集一致 - utf-8 设置Tomcat字符集为 ISO8859-1 tomcat/conf/server.xml URIEncoding=“ISO8859-1” Post请求默认字符集: ISO8859-1 request.setCharacterEncoding(“UTF-8”);修改tomcat默认字符编码：找到tomcat下的conf/server.xml文件 改为《Connector port=“8080” protocol=“HTTP/1.1” connectionTimeout=“20000” redirectPort=“8443” URIEncoding=“UTF-8” /》 package luanma; import javax.servlet.*; import javax.servlet.annotation.WebFilter; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletRequestWrapper; import java.io.IOException; import java.io.UnsupportedEncodingException; @WebFilter("/*") public class BmFilter implements Filter { public void destroy() { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException { HttpServletRequest request1= (HttpServletRequest) request; MyRequest myRequest=new MyRequest(request1); chain.doFilter(myRequest, response); } public void init(FilterConfig config) throws ServletException { } } //装饰者设计模式 /* 1.装饰者和被装饰者拥有相同的父接口 2.使用被装饰者 来 构建装饰者对象 3.重写需要增强的方法, 方法内部会使用到被装饰者原来的方法 4.将 被装饰者 包装成 装饰者对象 再去使用 */ class MyRequest extends HttpServletRequestWrapper { private HttpServletRequest request; public MyRequest(HttpServletRequest request) { super(request); this.request = request; } @Override public String getParameter(String name) { //先调用原来是乱码的参数值 String parameter = request.getParameter(name); //解决乱码 try { parameter=new String(parameter.getBytes("ISO-8859-1"),"UTF-8"); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } return parameter; } }

三。Listener: 监听器

四。自动登录

第一次登陆时将账号密码cooki发送。然后下回每次访问页面都被filter拦截的时候取出cooki，若符合就自动登陆 @WebServlet("/LoginServlet") public class LoginServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String username = request.getParameter("username"); String password = request.getParameter("password"); if(username.equals("lucy") && password.equals("1234f")){ if("checked".equals(request.getParameter("loginself"))){ Cookie cookie=new Cookie("username",username); Cookie cookie1=new Cookie("password",password); cookie.setMaxAge(Integer.MAX_VALUE); cookie1.setMaxAge(Integer.MAX_VALUE); cookie.setPath(request.getContextPath()); cookie1.setPath(request.getContextPath()); response.addCookie(cookie); response.addCookie(cookie1); } request.getSession().setAttribute("username",username); request.getSession().setAttribute("password",password); response.sendRedirect(request.getContextPath()+"/index.jsp"); } else { request.getRequestDispatcher("/login.jsp").forward(request,response); } } ------------------------------------------------------------------------ public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException { HttpServletRequest _request=(HttpServletRequest)request; Cookie[] cookies = _request.getCookies(); String username=null; String password=null; if(cookies!=null){ for(Cookie c:cookies){ if(c.getName().equals("username")){ username=c.getValue(); } if(c.getName().equals("password")){ password=c.getValue(); } } } if(username!=null&&password!=null){ if(username.equals("lucy")&&password.equals("1234f")){ _request.getSession().setAttribute("username",username); } } chain.doFilter(request, response); }