javaweb中servlet实现删除，删除数据库中的信息爆红

SQL语句不对,可以改为delete from t_user where id=?

这跟上个问题一样，你这是用类名调用的update，这个方法是非静态的，你需要用实例对象才行
另外update是更新吧，你是删除语句，删除语句 where后面缺少条件字段

直接类名.方法名，那你这个方法需要是static修饰的静态方法，sql语句也不对 delete from t_user where id=?

这不是跟上个问题一样吗
调用非静态的update方法

import org.apache.commons.dbutils.QueryRunner;

public class YourServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 创建QueryRunner实例
        QueryRunner queryRunner = new QueryRunner();

        // 调用非静态的update方法
        try {
            int result = queryRunner.update("DELETE FROM your_table WHERE id = ?", yourId);
            // 处理结果
        } catch (SQLException e) {
            e.printStackTrace();
            // 处理异常
        }
    }
}

这有个类似的问题, 你可以参考下: https://ask.csdn.net/questions/809269
我还给你找了一篇非常好的博客，你可以看看是否有帮助，链接：javaweb中servlet请求的转发
除此之外, 这篇博客: javaWeb之servlet获取表单数据中的 javaWeb之servlet获取表单数据 部分也许能够解决你的问题, 你可以仔细阅读以下内容或跳转源博客中阅读:

代码：
reg.jsp:

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'reg.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
    <style type="text/css">
     .label{
          width: 20%    
     }
     .controler{
          width: 80%    
     }
   </style>  
   <script type="text/javascript" src="js/Calendar3.js"></script>
  </head>

  <body>
    <h1>用户注册</h1>
    <hr>
    <form name="regForm" action="servlet/RegServlet" method="post" >
              <table border="0" width="800" cellspacing="0" cellpadding="0">
                <tr>
                    <td class="lalel">用户名：</td>
                    <td class="controler"><input type="text" name="username" /></td>
                </tr>
                <tr>
                    <td class="label">密码：</td>
                    <td class="controler"><input type="password" name="mypassword" ></td>

                </tr>
                <tr>
                    <td class="label">确认密码：</td>
                    <td class="controler"><input type="password" name="confirmpass" ></td>

                </tr>
                <tr>
                    <td class="label">电子邮箱：</td>
                    <td class="controler"><input type="text" name="email" ></td>

                </tr>
                <tr>
                    <td class="label">性别：</td>
                    <td class="controler"><input type="radio" name="gendar" checked="checked" value="Male">男<input type="radio" name="gendar" value="Female">女</td>

                </tr>

                <tr>
                    <td class="label">出生日期：</td>
                    <td class="controler">
                      <input name="birthday" type="text" id="control_date" size="10"
                      maxlength="10" onclick="new Calendar().show(this);" readonly="readonly" />
                    </td>
                </tr>
                <tr>
                    <td class="label">爱好：</td>
                    <td class="controler">
                    <input type="checkbox" name="favorite" value="nba"> NBA &nbsp;
                      <input type="checkbox" name="favorite" value="music"> 音乐 &nbsp;
                      <input type="checkbox" name="favorite" value="movie"> 电影 &nbsp;
                      <input type="checkbox" name="favorite" value="internet"> 上网 &nbsp;
                    </td>
                </tr>
                <tr>
                    <td class="label">自我介绍：</td>
                    <td class="controler">
                        <textarea name="introduce" rows="10" cols="40"></textarea>
                    </td>
                </tr>
                <tr>
                    <td class="label">接受协议：</td>
                    <td class="controler">
                        <input type="checkbox" name="isAccept" value="true">是否接受霸王条款
                    </td>
                </tr>
                <tr>
                    <td colspan="2" align="center">
                        <input type="submit" value="注册"/>&nbsp;&nbsp;
                        <input type="reset" value="取消"/>&nbsp;&nbsp;
                    </td>
                </tr>
              </table>
            </form>
  </body>
</html>

userinfo.jsp:

<%@ page language="java" import="java.util.*,java.text.*" contentType="text/html; charset=utf-8"%>

<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'userinfo.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
    <style type="text/css">
     .title{
         width: 30%;    
         background-color: #CCC;
         font-weight: bold;
     }
     .content{
         width:70%;
         background-color: #CBCFE5;
     }

   </style>  
  </head>

  <body>
    <h1>用户信息</h1>
    <hr>
    <center> 
     <jsp:useBean id="regUser" class="entity.Users" scope="session" />
     <table width="600" cellpadding="0" cellspacing="0" border="1">
        <tr>
          <td class="title">用户名：</td>
          <td class="content">&nbsp;<jsp:getProperty name="regUser" property="username"/></td>
        </tr>
        <tr>
          <td class="title">密码：</td>
          <td class="content">&nbsp;<jsp:getProperty name="regUser" property="mypassword"/></td>
        </tr>
        <tr>
          <td class="title">性别：</td>
          <td class="content">&nbsp;<jsp:getProperty name="regUser" property="gendar"/></td>
        </tr>
        <tr>
          <td class="title">E-mail：</td>
          <td class="content">&nbsp;<jsp:getProperty name="regUser" property="email"/></td>
        </tr>
        <tr>
          <td class="title">出生日期：</td>
          <td class="content">&nbsp;
              <% 
                  SimpleDateFormat sdf=new SimpleDateFormat("yyyy年MM月dd日");
                  String date=sdf.format(regUser.getBirthday());
              %>
              <%=date %>
          </td>
        </tr>
        <tr>
          <td class="title">爱好：</td>
          <td class="content">&nbsp;
            <% 
                String[] favorites=regUser.getFavorites();
                for(String f:favorites){


            %>
                <%=f %> &nbsp;&nbsp;
            <%
                }
            %>
          </td>
        </tr>
        <tr>
          <td class="title">自我介绍：</td>
          <td class="content">&nbsp;<jsp:getProperty name="regUser" property="introduce"/></td>
        </tr>
        <tr>
          <td class="title">是否介绍协议：</td>
          <td class="content">&nbsp;<jsp:getProperty name="regUser" property="flag"/></td>
        </tr>
     </table>
    </center>
  </body>
</html>

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <display-name></display-name>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>RegServlet</servlet-name>
    <servlet-class>servlet.RegServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>RegServlet</servlet-name>
    <url-pattern>/servlet/RegServlet</url-pattern>
  </servlet-mapping>    
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

Users.java:

package entity;

import java.util.Date;

//用户实体类
public class Users {

    private String username;
    private String mypassword;
    private String email;
    private String gendar;//性别
    private Date birthday;
    private String[] favorites;//爱好
    private String introduce;//自我介绍
    private boolean flag;//是否接受协议
    public Users() {
        super();
    }
    public Users(String username, String mypassword, String email,
            String gendar, Date birthday, String[] favorites, String introduce,
            boolean flag) {
        super();
        this.username = username;
        this.mypassword = mypassword;
        this.email = email;
        this.gendar = gendar;
        this.birthday = birthday;
        this.favorites = favorites;
        this.introduce = introduce;
        this.flag = flag;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getMypassword() {
        return mypassword;
    }
    public void setMypassword(String mypassword) {
        this.mypassword = mypassword;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    public String getGendar() {
        return gendar;
    }
    public void setGendar(String gendar) {
        this.gendar = gendar;
    }
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
    public String[] getFavorites() {
        return favorites;
    }
    public void setFavorites(String[] favorites) {
        this.favorites = favorites;
    }
    public String getIntroduce() {
        return introduce;
    }
    public void setIntroduce(String introduce) {
        this.introduce = introduce;
    }
    public boolean isFlag() {
        return flag;
    }
    public void setFlag(boolean flag) {
        this.flag = flag;
    }




}

regServlet.java:

package servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import entity.Users;

public class RegServlet extends HttpServlet {

    /**
     * Constructor of the object.
     */
    public RegServlet() {
        super();
    }

    /**
     * Destruction of the servlet. <br>
     */
    public void destroy() {
        super.destroy(); // Just puts "destroy" string in log
        // Put your code here
    }

    /**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        doPost(request,response);
    }

    /**
     * The doPost method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to post.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        request.setCharacterEncoding("utf-8");

        Users u = new Users();
        String username,mypassword,gendar,email,introduce,isAccept;
        Date birthday;
        String[] favorites;


        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        try
        {
            username = request.getParameter("username");
            mypassword = request.getParameter("mypassword");
            gendar = request.getParameter("gendar");
            email = request.getParameter("email");
            introduce = request.getParameter("introduce");
            birthday = sdf.parse(request.getParameter("birthday"));
            if(request.getParameterValues("isAccpet")!=null)
            {
              isAccept = request.getParameter("isAccept");
            }
            else
            {
              isAccept = "false";
            }
            //用来获取多个复选按钮的值
            favorites = request.getParameterValues("favorite");
            u.setUsername(username);
            u.setMypassword(mypassword);
            u.setGendar(gendar);
            u.setEmail(email);
            u.setFavorites(favorites);
            u.setIntroduce(introduce);
            if(isAccept.equals("true"))
            {
                u.setFlag(true);
            }
            else
            {
                u.setFlag(false);
            }
            u.setBirthday(birthday);

            //把注册成功的用户对象保存在session中
            //regUser和userinfo.jsp中的jsp:useBean的id进行对应
            request.getSession().setAttribute("regUser", u);
            //跳转到注册成功页面
            request.getRequestDispatcher("../userinfo.jsp").forward(request,response);
        }
        catch(Exception ex)
        {
            ex.printStackTrace();
        }


    }

    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException if an error occurs
     */
    public void init() throws ServletException {
        // Put your code here
    }

}

结果：
用户信息

用户名： 123
密码： 123
性别： Male
E-mail： 123
出生日期： 2016年10月02日
爱好： music movie internet
自我介绍： 123
是否介绍协议： false

小结：
1、我们自己编写的Servlet继承了HttpServlet类,一般只需覆盖doPost或者doGet方法,不必覆盖service( )方法,因为一个sevrvice( )方法是空的。
2、HttpServlet类扩展了GenericServlet类,实现了GenericServlet类的抽象方法sevrvice( )
3、HttpServlet类有两个sevrvice( )方法

您还可以看一下胡必腾老师的Java互联网开发筑基课课程中的 2.4.04 JavaWeb WEB开发第一个Servlet小节, 巩固相关知识点