一段较为完整的程序

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ page import="java.util.*" %>
    <%@ page import="com.hanqi.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>用户列表   先启动FindUserList</title>
</head>
<body>
<%

Object obj = request.getAttribute("userlist");

if(obj != null)
{
    ArrayList<User> array = (ArrayList<User>)obj;
    
    //遍历
    for(User u : array)
    {
        out.print(u.getUserID() + "	  " + u.getUserName() + "	 " + u.getPassword() + "	 " +u.getUserTime()+
                "	 <a href='DeleteUser?userid="+u.getUserID()+"'>删除</a>"
        +"<form action='EditUser' method='get' >"+
                "<input type='hidden' name='userid' value='"+ u.getUserID() +"' />"
                +" 用户名称:<input type='text' name='username' value='" + u.getUserName() + "' />"
        +"用户密码：<input type='password' name='password' value='"+u.getPassword()+"' />"
        +"<input type='submit' value='提交' /></form>"+
        ""
                        +"<br>");
    }
    //DeleteUser?  ?是要删除的userid
    
    
}
else
{
    out.append("用户列表为空");
}

%>

<br>
<br>
<br>

<a href="zhuce.jsp">注册新用户</a>
</body>
</html>
ShowUserList
package com.hanqi;

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.*;

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

/**
 * Servlet implementation class FindUserList
 */
public class FindUserList extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public FindUserList() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        //
        request.setCharacterEncoding("UTF-8");    
        response.setContentType("text/html;charset=UTF-8");
        response.setCharacterEncoding("UTF-8");    
        
        try 
        {
            //加载数据库驱动，并注册到驱动管理器
            Class.forName("oracle.jdbc.driver.OracleDriver");
            //数据库连接字符串
            String url = "jdbc:oracle:thin:@localhost:1521:orcl";
            //获取connection对象 （个人理解为登陆数据库 并将数据关联）
            Connection conn = DriverManager.getConnection(url,"test","123654789");    //url,名称，密码
            //判断是否有数据
            if(conn != null)
            {
                //操纵数据库
                String sql = "select * from t_user";
                
                //执行sql语句的类
/*                 PreparedStatement pps = conn.prepareStatement(sql);        */
                Statement stm = conn.createStatement();
                //执行查询，返回结果集
                ResultSet rs = stm.executeQuery(sql);
                //数组的方式来进行  装载  和  传输
                ArrayList<User> array = new ArrayList<User>();//将数据装载在数组中放置到其他地方进行输出

                if(rs != null)
                {
                    //遍历结果集
                    while(rs.next())
                    {
                        //实体类装载记录
                        User u  = new User();
                        u.setUserID(rs.getString("USER_ID"));
                        u.setUserName(rs.getString("USER_NAME"));
                        u.setPassword(rs.getString("PASSWORD"));
                        u.setUserTime(rs.getString("USER_TIME"));
                        
                        /*
                        //取值 要按照相应类型来取
                        rs.getString("");        // 按字段名来取
                        rs.getString(0);        // 括号内 columnIndex 是 列的序号 字段序号是从  1  开始算的
                        rs.getDouble(0);        //注意要取值的类型
                        */
                        
                        //将装载的数据传输
                        array.add(u);
                        response.getWriter().append("USER_ID = "+ rs.getString("USER_ID")+";<br>");
                        response.getWriter().append("USER_NAME = "+ rs.getString("USER_NAME")+";<br>");
                        response.getWriter().append("PASSWORD = "+ rs.getString("PASSWORD")+";<br>");
                        response.getWriter().append("USER_TIME = "+ rs.getString("USER_TIME")+";<br>");
                    }
                    request.setAttribute("userlist", array);
                    
                    //释放
                    rs.close();
                }
                else
                {
                    response.getWriter().append("结果集为空");
                }
                //关闭  释放资源
                stm.close();
                
                conn.close();
                
            }
            else
            {
                
            }
            
        }
        catch (ClassNotFoundException e)        //仅捕获一类特定异常 
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
            response.getWriter().append(e.getMessage());
        }
        catch (Exception e)                     //捕获所有异常
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
            response.getWriter().append(e.getMessage());
        }
        //页面跳转
        request.getRequestDispatcher("ShowUserList.jsp").forward(request,response);
        
    }

    private void zhuanma() {
        // TODO Auto-generated method stub
        
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
FindUserList
package com.hanqi.common;

import java.sql.*;

public class DBHelper {

    //获取connection对象   static 静态方法 不需要调用他的实例化
    public static Connection getConnection() throws Exception    //工具类中异常不要用try catch
    {
        
        //加载数据库驱动，并注册到驱动管理器
        Class.forName("oracle.jdbc.driver.OracleDriver");
        //数据库连接字符串
        String url = "jdbc:oracle:thin:@localhost:1521:orcl";
        //获取connection对象 （个人理解为登陆数据库 并将数据关联）
        Connection conn = DriverManager.getConnection(url,"test","123654789");    //url,名称，密码
        
        return conn;
        
    }
    
}
--封装类--
package com.hanqi;

import java.io.IOException;
import java.sql.*;
import java.text.SimpleDateFormat;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.hanqi.*;
import java.util.*;
import java.util.Date;
/**
 * Servlet implementation class SaveUser
 */
public class SaveUser extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public SaveUser() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //转码，固定写法
        request.setCharacterEncoding("UTF-8");    
        response.setContentType("text/html;charset=UTF-8");
        response.setCharacterEncoding("UTF-8");    
        
        //获取当前时间
        Date dt = new Date();
        //格式化时间
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String sj = sdf.format(dt);
        
        
        
        
        //获取内容
        String userID = request.getParameter("userid");
        String userName = request.getParameter("username");
        String pw = request.getParameter("password");
        
        //判断输入的内容
        if(userID == null || userID.trim().length() == 0)
        {
            //输出内容
            response.getWriter().append("用户代码不能为空");
        }
        else if(userName == null || userName.trim().length() == 0)
        {
            response.getWriter().append("用户姓名不能为空");
        }
        else
        {
            try 
            {
                //加载数据库驱动，并注册到驱动管理器
                Class.forName("oracle.jdbc.driver.OracleDriver");
                //数据库连接字符串
                String url = "jdbc:oracle:thin:@localhost:1521:orcl";
                //获取connection对象 （个人理解为登陆数据库 并将数据关联）
                Connection conn = DriverManager.getConnection(url,"test","123654789");    //url,名称，密码
                
                //判断是否有数据
                if(conn != null)
                {
                    //操纵数据库        
                    String sql = "insert into t_user (user_id，user_name,password,user_time) values (?,?,?,?)";
                    
                    //另外一种方法：
                    //String sql = "insert into t_user (user_id,user_name,password) values ('" + userID + "')";
                    
                    //执行sql语句的类
                    PreparedStatement pps = conn.prepareStatement(sql);
                    
                    //转码
                    userName = new String(userName.getBytes("ISO-8859-1"),"UTF-8");      
                    //post 提交方式不用转码  get方式需要转码
                    
                    
                    //将操纵数据库中数据类名编下顺序便于输入
                    pps.setString(1, userID);
                    pps.setString(2, userName);
                    pps.setString(3, pw);
                    pps.setString(4, sj);
                    
                    
                    
                    
                    int row = pps.executeUpdate();     //执行sql语句并返回所影响的行数
                    
                    if(row > 0)
                    {
                        //response.getWriter().append("保存"+ row +"条数据成功");
                        response.sendRedirect("FindUserList");        //直接跳转到用户列表
                    }
                    else
                    {
                        response.getWriter().append("保存数据失败");
                    }
                    //关闭  释放资源
                    pps.close();
                    
                    conn.close();
                    
                }
                else
                {
                    
                }
                
            }
            catch (Exception e)        //仅捕获一类特定异常 
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
                response.getWriter().append(e.getMessage());
            }
            
            
            
        }
    }

    private void zhuanma() {
        // TODO Auto-generated method stub
        
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
SaveUser
package com.hanqi;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.hanqi.common.DBHelper;

import java.sql.*;


/**
 * Servlet implementation class DeleteUser
 */
public class DeleteUser extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DeleteUser() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        //转码
                request.setCharacterEncoding("UTF-8");    
                response.setContentType("text/html;charset=UTF-8");
                response.setCharacterEncoding("UTF-8");    
                
                String userid = request.getParameter("userid");
                if(userid != null && userid.trim().length() > 0)
                {
                    try 
                    {
                        Connection conn = DBHelper.getConnection();        //DBHelper 静态方法 不需要实例化
                        if(conn != null)
                        {
                        //    String sql = "delete from t_user where user_id = '"+userid+"'";    //直接组合  
                            String sql = "delete from t_user where user_id = ?";            //使用占位符
                            
                            PreparedStatement pst = conn.prepareStatement(sql);
                            
                            pst.setString(1, userid);
                            int row = pst.executeUpdate();        //返回数值  数值代表删除的行数
                            response.sendRedirect("FindUserList");
                            pst.close();
                            conn.close();
                        }
                        
                    } 
                    
                    catch (Exception e) 
                    {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                else
                {
                    response.getWriter().append("userid不能为空！");
                }
        
        
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
DeleteUser
package com.hanqi;

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

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

import com.hanqi.common.DBHelper;

/**
 * Servlet implementation class EditUser
 */
public class EditUser extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public EditUser() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        request.setCharacterEncoding("UTF-8");    
        response.setContentType("text/html;charset=UTF-8");
        response.setCharacterEncoding("UTF-8");    
        
        //接受相关参数
        String userID = request.getParameter("userid");
        String userName = request.getParameter("username");
        String pw = request.getParameter("password");
        //判断输入的内容
                if(userID == null || userID.trim().length() == 0)
                {
                    //输出内容
                    response.getWriter().append("用户代码不能为空");
                }
                else if(userName == null || userName.trim().length() == 0)
                {
                    response.getWriter().append("用户姓名不能为空");
                }
                else
                {
                    try 
                    {
                        Connection conn = DBHelper.getConnection();
                        if(conn != null)
                        {
                            //操纵数据库        select sysdate from dual;
                            String sql = "update t_user set user_name = ?, password = ? where user_id = ?";
                            
                            //另外一种方法：
                            //String sql = "insert into t_user (user_id,user_name,password) values ('" + userID + "')";
                            
                            //执行sql语句的类
                            PreparedStatement pps = conn.prepareStatement(sql);
                            
                            //转码
                            userName = new String(userName.getBytes("ISO-8859-1"),"UTF-8");      
                            //post 提交方式不用转码  get方式需要转码
                            
                            
                            //将操纵数据库中数据类名编下顺序便于输入
                            pps.setString(3, userID);
                            pps.setString(1, userName);
                            pps.setString(2, pw);
                            
                            
                            int row = pps.executeUpdate();     //执行sql语句并返回所影响的行数
                            
                            //关闭  释放资源
                            
                            pps.close();
                            
                            conn.close();
                            
                            response.sendRedirect("FindUserList");
                            /*
                            if(row > 0)
                            {
                                response.getWriter().append("保存"+ row +"条数据成功");
                            }
                            else
                            {
                                response.getWriter().append("保存数据失败");
                            }
                            
                            
                            */
                            
                            
                        }
                        else
                        {
                            
                        }
                        
                    }
                    catch (Exception e)        //仅捕获一类特定异常 
                    {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                        response.getWriter().append(e.getMessage());
                    }
                }
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
EditUser
package com.hanqi;

    //关于用户的实体类
public class User 
{
    //用户代码
    private String UserID;
    
    public String getUserID()
    {
        return UserID;
    }
    public void setUserID(String userID)
    {
        this.UserID = userID;
    }
    //用户名称
    private String UserName;

    public String getUserName() {
        return UserName;
    }
    public void setUserName(String userName) {
        UserName = userName;
    }

    //密码
    private String Password;
    
    public String getPassword() {
        return Password;
    }
    public void setPassword(String password) {
        Password = password;
    }
    //时间
    private String UserTime;

    public String getUserTime() {
        return UserTime;
    }
    public void setUserTime(String userTime) {
        UserTime = userTime;
    }
    
    
    
}
User
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>用户注册</title>
<script type="text/javascript">
function yanz()
{
    if  (zhugan.userid.value == "")
        {
            alert("用户代码不能为空！");
            return false;
        }
    if(zhugan.username.value == "")
        {
            alert("用户名称不能为空！");
            return false;
        }
    if(zhugan.password.value == "")
        {
        alert("登陆密码不能为空！");
        return false;
        }
    /*
    if(zhugan.passwore.value == "")
        {
            alert("确认密码不能为空！");
            return false;
            }
    */
    if(zhugan.password.value != zhugan.passwore.value)
    {
        alert("登陆密码与确认密码不相同！");
        return false;
    }
return true;
}
</script>
</head>
<body>
<form id="zhugan" action="SaveUser"  method="get"  onSubmit="return yanz();">      
用户代码：<input id="userid" type="text" name="userid" width=30 />
<br><br>
用户名称：<input id="username" type="text" name="username" width=30 />
<br><br>
登录密码：<input id="password" type="password" name="password" width=30 />
<br><br>
确认密码：<input id="passwore" type="password" name="pueren" width=30 />
<br><br>
<input type="submit" value="提交" />
</form>
</body>
</html>
注册页面
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原文地址：https://www.cnblogs.com/name-hanlin/p/5027591.html