JavaWeb学习笔记20/10/27Filter

Filter

过滤器，用来过滤网站的数据

• 处理中文乱码
• 登录验证
  

Filter开发步骤：

1. 导包(导javax.servlet的包，不要导错了)

2. 编写过滤器,实现Filter接口，重写对应的方法即可

   public class CharacterEncodingFilter implements Filter {
         
         
   
       //初始化
       public void init(FilterConfig filterConfig) throws ServletException {
         
         
           System.out.println("CharacterEncodingFilter初始化");
       }
   
       public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
         
         
           //Chain：链
           /*
           1.过滤中的所有代码,在过滤特定请求的时候都会执行
           2.必须要让过滤器然续同行
               filterChain.doFilter(servletRequest,servletResponse);
           */
           servletRequest.setCharacterEncoding("utf-8");
           servletResponse.setCharacterEncoding("utf-8");
           servletResponse.setContentType("text/html;charset=UTF-8");
   
           System.out.println("CharacterEncodingFilter执行前...");
           filterChain.doFilter(servletRequest,servletResponse);//让我们的请求继续走，如果不写，程序到这里就被拦截停止
           System.out.println("CharacterEncodingFilter执行后...");
       }
       //销毁
       public void destroy() {
         
         
           System.out.println("CharacterEncodingFilter销毁");
       }
   }
   

3. 在Web.xml中配置Filter

   <filter>
       <filter-name>CharacterEncodingFilter</filter-name>
       <filter-class>com.weng.filter.CharacterEncodingFilter</filter-class>
   </filter>
   <filter-mapping>
       <filter-name>CharacterEncodingFilter</filter-name>
       <!--只要是Servlet下的任何请求，都会经过这个过滤器-->
       <url-pattern>/Servlet/*</url-pattern>
   </filter-mapping>