1. 自定义实现Filter接口实现类

1.1 在doFilter里实现自身需求的请求与响应拦截

package com.test.filter;

import javax.servlet.*;
import java.io.IOException;

public class TestFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        /*
        * 登录用户验证
        * */
        if (servletRequest.getParameter("name").equals("sunlight")) {
            filterChain.doFilter(servletRequest, servletResponse);
        } else {
            servletResponse.setCharacterEncoding("UTF-8");
            servletResponse.setContentType("text/html;UTF-8");
            servletResponse.getWriter().write("用户名称输入不正确");
        }
        System.out.println("过滤器拦截");
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void destroy() {

    }
}

2. 在webapp/WEB-INF/web.xml配置filter

<filter>
    <filter-name>testFilterConfig</filter-name>
    <filter-class>com.test.filter.TestFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>testFilterConfig</filter-name>
    <url-pattern>/testForm</url-pattern>
  </filter-mapping>

filter-name 过滤名称设置，自定义即可
filter-class 生效的过滤器类
url-pattern 过滤器匹配规则
注 filter-mapping 里的filter-name需与filter里的filter-name保持一致

3.实现效果