第一个filter
package com.filter;import java.io.UnsupportedEncodingException;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.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class CommentFilter implements Filter{ private FilterConfig config;//定义属性，保存容器传过来的参数 /** * 容器启动之后会立即创建过滤器实例(通过调用构造器) * 注；只会创建一个实列 */ public CommentFilter() { System.err.println("CommentFilter构造器被调用"); } /** * 容器在创建爱你好过滤器之后，会立即调用该实列的init方法（初始化方法） * 注； * 该方法只会执行一次 * 容器会将FilterConfig对象作为参数传进来，可以利用该对象读取参数初始化参数 */ public void init(FilterConfig filterConfig) throws ServletException { config = filterConfig; System.err.println("容器的init方法被调用了"); } /** * 容器绶带请求之后，会调用doFilter方法处理请求 * 容器会将请求对象和响应对象作为参数传进来 * 注 * ServletRequest是httpServletRequest的父接口 * ServletResponse是httpServletResponse的父接口 * 这儿没有用字接口，是过渡设计的产物 * FilterChain chain---过滤器链，如果调用了FilterChain chain对象的doFilter方法，表示向后调用， * 负责，中断请求，返回处理结果 * * * */ public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain chain) { System.err.println("CommentFilter的doFilter开始执行"); HttpServletRequest request = (HttpServletRequest)arg0; HttpServletResponse response = (HttpServletResponse)arg1; try { request.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=utf-8"); String content = request.getParameter("content"); //调用FilterConfig对象的方法来读取初始化参数 String illegal = config.getInitParameter("illegal");//玫感字 System.out.println(illegal); if(content.indexOf(illegal) != -1) { //包含美感字，不再向后调用 response.getWriter().print("评论的内容包含了美感字"); }else { //没有包含美感字，则继续向后调用，Filter链doFilter的方法 chain.doFilter(request, response); } } catch (Exception e) { e.printStackTrace(); } System.err.println("CommentFilter的doFilter执行完毕"); } //当容器删除过滤器实列之前，会先调用该实列的destroy方法，该方法只执行一次 public void destroy() { System.err.println("容器被销毁了destroy"); }
}
第二个filter
package com.filter;import java.io.IOException;import java.io.PrintWriter;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.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class CountFilter implements Filter{ private FilterConfig config; public void init(FilterConfig filterConfig) throws ServletException { config = filterConfig; } public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain chain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest)arg0; HttpServletResponse response = (HttpServletResponse)arg1; PrintWriter out = response.getWriter(); request.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=utf-8"); String lengthsize = config.getInitParameter("length");//字数 String content = request.getParameter("content");//获取评论的内容 if(content.length() >Integer.parseInt(lengthsize)) {//评论的字数如果大于10 response.getWriter().print("您输入的字数过长"); }else { //没有包含美感字，则继续向后调用，Filter链doFilter的方法 chain.doFilter(request, response); } } public void destroy() { }
}
web.xml配置文件
需要配置过滤器和初始化参数，
