Servlet简单实现前端和后端的增删改查功能的实现
简单的sevlet项目来实现增删改查操作
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本文主要是一些简单的学习心得：
1.首先创建本地的Mysql数据库
2.然后要了解到MVC模式，然后在idea中创建动态的java-web模块，并分在不同的文件夹里实现不同的操作
3.在webapp下创建static文件夹，导入js文件
4.然后再WEB-INF文件夹导入相应的jar包
4.在webapp文件下创建前端的页面user.jsp
<%--
Created by IntelliJ IDEA.
User: DELL
Date: 2022/8/8
Time: 10:08
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>用户列表</title>
<link rel="stylesheet" href="static/css/bootstrap.min.css">
<script src="static/js/jquery-1.11.3.min.js"></script>
<script src="static/js/bootstrap.min.js"></script>
<script src="static/js/jqPaginator.js"></script>
</head>
<body>
<-- 搜索框 -->
<div class="container-fluid">
<div class="row">
<div class="col-md-4">
<form class="form-inline">
<div class="form-group">
<label class="sr-only" for="user_name">用户名</label>
<input type="text" class="form-control" id="user_name" placeholder="用户名">
</div>
<div class="form-group">
<label class="sr-only" for="user_tel">电话</label>
<input type="tel" class="form-control" id="user_tel" placeholder="电话">
</div>
<button type="button" class="btn btn-primary" onclick="queryUser()">搜索</button>
</form>
</div>
<div class="col-md-2">
<button type="button" class="btn btn-primary" data-toggle='modal' data-target='#myModal1'>添加用户</button>
</div>
</div>
</div>
<!-- Table-->
<table class="table table-hover">
<thead>
<tr>
<th>用户名</th>
<th>年龄</th>
<th>性别</th>
<th>电话</th>
<th>操作</th>
</tr>
</thead>
<tbody id="tab">
</tbody>
<tfoot>
<tr>
<td colspan="8" style="">
<ul class="pagination" id="pagination1"></ul>
</td>
</tr>
</tfoot>
</table>
<!-- Modal修改 -->
<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
<div class="modal-dialog" role="document">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">×</span></button>
<h4 class="modal-title" id="myModalLabel">用户修改</h4>
</div>
<div class="modal-body">
<form class="form-horizontal">
<%--隐藏域(存放id值)--%>
<input type="hidden" id="userId">
<div class="form-group">
<label for="username" class="col-sm-2 control-label">用户名</label>
<div class="col-sm-10">
<input type="text" class="form-control" id="username" placeholder="用户名">
</div>
</div>
<div class="form-group">
<label for="userage" class="col-sm-2 control-label">年龄</label>
<div class="col-sm-10">
<input type="number" class="form-control" id="userage" placeholder="年龄">
</div>
</div>
<div class="form-group">
<label class="col-sm-2 control-label">性别</label>
<div class="col-sm-10">
<div class="radio-inline">
<input type="radio" name="sex" id="sex1" value="男">男
</div>
<div class="radio-inline">
<input type="radio" name="sex" id="sex2" value="女">女
</div>
</div>
</div>
<div class="form-group">
<label for="usertel" class="col-sm-2 control-label">电话</label>
<div class="col-sm-10">
<input type="tel" class="form-control" id="usertel" placeholder="电话">
</div>
</div>
</form>
</div>
<div class="modal-footer">
<button type="button" class="btn btn-default" data-dismiss="modal">关闭</button>
<button type="button" class="btn btn-primary" onclick="updateUser()">保存</button>
</div>
</div>
</div>
</div>
<!-- Modal(添加) -->
<div class="modal fade" id="myModal1" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
<div class="modal-dialog" role="document">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">×</span></button>
<h4 class="modal-title">用户添加</h4>
</div>
<div class="modal-body">
<form class="form-horizontal">
<div class="form-group">
<label for="username" class="col-sm-2 control-label">用户名</label>
<div class="col-sm-10">
<input type="text" class="form-control" id="username1" placeholder="用户名">
</div>
</div>
<div class="form-group">
<label for="userage" class="col-sm-2 control-label">年龄</label>
<div class="col-sm-10">
<input type="number" class="form-control" id="userage1" placeholder="年龄">
</div>
</div>
<div class="form-group">
<label class="col-sm-2 control-label">性别</label>
<div class="col-sm-10">
<div class="radio-inline">
<input type="radio" name="gender" id="gender1" value="男">男
</div>
<div class="radio-inline">
<input type="radio" name="gender" id="gender2" value="女">女
</div>
</div>
</div>
<div class="form-group">
<label for="usertel" class="col-sm-2 control-label">电话</label>
<div class="col-sm-10">
<input type="tel" class="form-control" id="usertel1" placeholder="电话">
</div>
</div>
</form>
</div>
<div class="modal-footer">
<button type="button" class="btn btn-default" data-dismiss="modal">关闭</button>
<button type="button" class="btn btn-primary" onclick="addUser()">提交</button>
</div>
</div>
</div>
</div>
</body>
</html>
样式设置如下图所示
5.在后端的entity文件夹放的是实体类User
package com.xhu.fy.entity;
public class User {
private Integer id;
private String userName;
private String userAge;
private String userSex;
private String userTel;
private String userPwd;
public User(Integer id, String userName, String userAge, String userSex, String userTel, String userPwd) {
this.id = id;
this.userName = userName;
this.userAge = userAge;
this.userSex = userSex;
this.userTel = userTel;
this.userPwd = userPwd;
}
public User() {
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserAge() {
return userAge;
}
public void setUserAge(String userAge) {
this.userAge = userAge;
}
public String getUserSex() {
return userSex;
}
public void setUserSex(String userSex) {
this.userSex = userSex;
}
public String getUserTel() {
return userTel;
}
public void setUserTel(String userTel) {
this.userTel = userTel;
}
public String getUserPwd() {
return userPwd;
}
public void setUserPwd(String userPwd) {
this.userPwd = userPwd;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", userName='" + userName + '\'' +
", userAge='" + userAge + '\'' +
", userSex='" + userSex + '\'' +
", userTel='" + userTel + '\'' +
", userPwd='" + userPwd + '\'' +
'}';
}
}
6.再Utils写连接数据库的工具类
package com.xhu.fy.utils;
import java.sql.*;
public class DBUtil {
static {
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
public static Connection getCon(){
try {
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=UTF-8", "root", "123456");
return con;
} catch (SQLException throwables) {
throwables.printStackTrace();
return null;
}
}
public static void closeAll(ResultSet rs, PreparedStatement ps,Connection con){
if (rs!=null){
try {
rs.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
if (ps!=null){
try {
ps.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
if (con!=null){
try {
con.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
}
}
注意：此方法是用的Class.forName的方法
在getCon方法里加上?useUnicode=true&characterEncoding=UTF-8防止前端进行修改后出现“？
编写分页的工具类PageUtil
package com.xhu.fy.utils;
import java.util.List;
public class PageUtil<T> {
//总页数
private int totalPages;
//每页展示条数
private int pageSize;
//当前页码
private int currentPage;
//总条数
private int totalCounts;
//存放查询出的数据
private List<T> pageInfo;
public int getTotalPages() {
return totalPages;
}
public void setTotalPages(int totalPages) {
this.totalPages = totalPages;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
public int getTotalCounts() {
return totalCounts;
}
public void setTotalCounts(int totalCounts) {
this.totalCounts = totalCounts;
}
public List<T> getPageInfo() {
return pageInfo;
}
public void setPageInfo(List<T> pageInfo) {
this.pageInfo = pageInfo;
}
}
7.在前端页面使用Ajax方法实现局部刷新的功能，查询数据库中所有的数据并实现分页功能
var total = 0;//总条数
var visiblePages = 5;//显示的分页按钮数
var current_Page = 0;//当前页码
var pageSize = 5;//每页展示的条数
/*
页面加载完毕就执行
*/
$(function () {
showUser(-1);
pageInit();
});分页插件的初始化
/**
* 分页插件初始化
* 注意：要么设置totalPages，要么设置totalCounts + pageSize，否则报错；设置了totalCounts和pageSize后，会自动计算出totalPages。
*/
function pageInit() {
$('#pagination1').jqPaginator({
pageSize:pageSize,
visiblePages:visiblePages,
currentPage:current_Page,
totalCounts:total,
first: '<li class="first"><a href="javascript:void(0);">第一页</a></li>',
prev: '<li class="prev"><a href="javascript:void(0);">前一页</a></li>',
next: '<li class="next"><a href="javascript:void(0);">下一页</a></li>',
last: '<li class="last"><a href="javascript:void(0);">最后一页</a></li>',
page: '<li class="page"><a href="javascript:void(0);">{{page}}</a></li>',
onPageChange: function (num) {
/* num代表改变过后的页码 */
showUser(num);
}
});
}/*
查询全部信息
*/
function showUser(pageNum) {
$.ajax({
url:"user",
type:"POST",
async:false,//同步请求
dataType:"json",
data:{"_method":"queryUser","pageNum":pageNum,"pageSize":pageSize},
success:function (data) {
if (pageNum==-1){//如果pageNum==-1，代表第一次访问
total=data.totalCounts;
current_Page=data.pageNum;
}
var str = "";
for(var i=0;i<data.pageInfo.length;i++){
str+="<tr><td>"+data.pageInfo[i].userName+"</td><td>"+data.pageInfo[i].userAge+"</td><td>"+data.pageInfo[i].userSex+"</td><td>"+
+data.pageInfo[i].userTel+"</td>"+
"<td><button type='button' class='btn btn-danger' onclick='deleteUser("+data.pageInfo[i].id+")'>删除</button>"+
"<button type='button' class='btn btn-primary' data-toggle='modal' data-target='#myModal' onclick='findUserById("+data.pageInfo[i].id+")'>修改</button></td></tr>";
}
$("#tab").html(str);
}
});
}向后端传递一个查询方法queryUser
在控制层controller里创建一个实现请求转发的servlet，重写方法doGET和doPost
String method = req.getParameter("_method");
if (method.equals("queryUser")){
queryUser(req,resp);
}//获取方法名，并实现该方法 public void queryUser(HttpServletRequest req, HttpServletResponse resp) throws IOException {
String pageNum = req.getParameter("pageNum");
String pageSize = req.getParameter("pageSize");
resp.setContentType("text/html;charset=utf-8");
PageUtil<User> pageUtil = userService.queryUserPage(pageNum,pageSize);
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(pageUtil);
resp.getWriter().write(json);
}调用service层内封装的dao层的方法queryUserPage
编写service的接口
PageUtil<User> queryUserPage(String pageNum,String pageSize);在serviceImpl实现类实现该方法
private UserDao userDao=new UserDaoImpl();
@Override
public PageUtil<User> queryUserPage(String pageNum,String pageSize) {
int pageNum1 = Integer.parseInt(pageNum);
if (pageNum1==-1){
pageNum1=1;
}
PageUtil<User> userPageUtil = new PageUtil<>();
int totalCounts = userDao.selectCountAll();
userPageUtil.setTotalCounts(totalCounts);
userPageUtil.setPageSize(Integer.parseInt(pageSize));
userPageUtil.setCurrentPage(pageNum1);
List<User> users = userDao.selectUser(pageNum1, Integer.parseInt(pageSize));
userPageUtil.setPageInfo(users);
return userPageUtil;
}调用dao层的方法来访问数据库中的数据
编写dao层的接口
List<User> selectUser(int pageNum,int pageSize);在dao层实现类daoImpl实现该方法
private Connection con = null;
private PreparedStatement ps = null;
private ResultSet rs = null;
@Override
public List<User> selectUser(int pageNum,int pageSize) {
con = DBUtil.getCon();
String sql="select * from user limit ?,?";
try {
ps = con.prepareStatement(sql);
ps.setInt(1,(pageNum-1)*pageSize);
ps.setInt(2,pageSize);
rs = ps.executeQuery();
List<User> users=new ArrayList<>();
while (rs.next()){
User user = new User();
user.setId(rs.getInt("id"));
user.setUserName(rs.getString("userName"));
user.setUserAge(rs.getString("userAge"));
user.setUserSex(rs.getString("userSex"));
user.setUserTel(rs.getString("userTel"));
user.setUserPwd(rs.getString("userPwd"));
users.add(user);
}
return users;
} catch (SQLException throwables) {
throwables.printStackTrace();
}finally {
DBUtil.closeAll(rs,ps,con);
}
return null;
}8.实现删除数据的功能
在前端删除按钮定义一个点击方法，使用ajax局部刷新
/*
删除
*/
function deleteUser(id){
var isDelete=confirm("确认是否删除?");
if (isDelete){
$.ajax({
url: "user",
type: "get",
data: {"id":id,"_method":"deleteUser"},
dataType: "text",
success:function (data){
if (data="success"){
showUser();
}
}
});
}
}注意：为了防止用户不小心数据，所以改在删除增加一个提示框
定义的方法名为deleteUser
后端controller层来接受
else if (method.equals("deleteUser")){
deleteUser(req,resp);
}public void deleteUser(HttpServletRequest req, HttpServletResponse resp) throws IOException {
String id = req.getParameter("id");
int id1 = Integer.parseInt(id);
String mess = userService.deleteUserById(id1);
resp.setContentType("text/html;charset=utf-8");
resp.getWriter().write(mess);
}通过主键id来进行删除
同理调用的service层封装的方法
String deleteUserById(int id); @Override
public String deleteUserById(int id) {
int num = userDao.deleteUserById(id);
if(num>0){
return "success";
}else {
return "fail";
}
}dao层的方法
int deleteUserById(int id);@Override
public int deleteUserById(int id) {
con = DBUtil.getCon();
String sql = "delete from user where id = ?";
try {
ps = con.prepareStatement(sql);
ps.setInt(1,id);
int num = ps.executeUpdate();
return num;
} catch (SQLException throwables) {
throwables.printStackTrace();
}finally {
DBUtil.closeAll(rs,ps,con);
}
return 0;
}9.实现修改数据的功能
在点击修改功能后，应该弹出一个新的模态框，内容为该数据的内容，可在上面进行修改和保存
首先要查询该指定用户的信息放在模态框上显示
/*
根据id查询用户
*/
function findUserById(id){
$.ajax({
url:"user",
type:"get",
data:{"_method":"queryUserById","id":id},
dataType:"json",
success:function (data){
$("#userId").val(data.id);
$("#username").val(data.userName);
$("#userage").val(data.userAge);
if (data.userSex=="男"){
$("#sex1").prop("checked",true);
}else if(data.userSex=="女"){
$("#sex2").prop("checked",true);
}
$("#usertel").val(data.userTel);
}
});
}并进入到controller层
else if (method.equals("queryUserById")){
queryUserById(req, resp);
}public void queryUserById(HttpServletRequest req, HttpServletResponse resp) throws IOException {
String id = req.getParameter("id");
int id1 = Integer.parseInt(id);
resp.setContentType("text/html;charset=utf-8");
User user = userService.queryUserById(id1);
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(user);
resp.getWriter().write(json);
}根据id值来查询当前的用户信息
service层的方法实现
User queryUserById(int id); @Override
public User queryUserById(int id) {
return userDao.selectUserById(id);
}dao层方法实现
User selectUserById(int id);@Override
public User selectUserById(int id) {
con = DBUtil.getCon();
String sql="select * from user where id=?";
try {
ps = con.prepareStatement(sql);
ps.setInt(1,id);
rs = ps.executeQuery();
if (rs.next()){
User user = new User();
user.setId(rs.getInt("id"));
user.setUserName(rs.getString("userName"));
user.setUserAge(rs.getString("userAge"));
user.setUserSex(rs.getString("userSex"));
user.setUserTel(rs.getString("userTel"));
user.setUserPwd(rs.getString("userPwd"));
return user;
}
} catch (SQLException throwables) {
throwables.printStackTrace();
}finally {
DBUtil.closeAll(rs,ps,con);
}
return null;
}查询到数据后显示在模态框内，如图所示
修改用户的值
/*
修改用户信息
*/
function updateUser(){
//获取修改完后得表单值
var userId = $("#userId").val()
var userName = $("#username").val();
var userSex = $("input[name='sex']:checked").val();
var userAge = $("#userage").val();
var userTel = $("#usertel").val();
$.ajax({
url:"user",
type:"POST",
data:{
"userId":userId,
"userName":userName,
"userSex":userSex,
"userAge":userAge,
"userTel":userTel,
"_method":"updateUserById"
},
dataType:"text",
success:function (data){
if (data=="success"){
$('#myModal').modal('hide');
showUser();
}
}
});
}controller层
else if (method.equals("updateUserById")){
updateUserById(req,resp);
}public void updateUserById(HttpServletRequest req, HttpServletResponse resp) throws IOException {
req.setCharacterEncoding("utf-8");
String id = req.getParameter("userId");
String userName = req.getParameter("userName");
String userSex = req.getParameter("userSex");
String userAge = req.getParameter("userAge");
String userTel = req.getParameter("userTel");
User user = new User();
user.setId(Integer.parseInt(id));
user.setUserName(userName);
user.setUserSex(userSex);
user.setUserAge(userAge);
user.setUserTel(userTel);
String mess = userService.updateUserById(user);
resp.setContentType("text/html;charset=utf-8");
resp.getWriter().write(mess);
}service层
String updateUserById(User user); @Override
public String updateUserById(User user) {
int num = userDao.updateUserById(user);
if(num>0){
return "success";
}else {
return "fail";
}
}dao层
int updateUserById(User user);@Override
public int updateUserById(User user) {
con=DBUtil.getCon();
String sql="update user set userName=?,userAge=?,userSex=?,userTel=? where id=?";
try {
ps=con.prepareStatement(sql);
ps.setString(1,user.getUserName());
ps.setString(2,user.getUserAge());
ps.setString(3,user.getUserSex());
ps.setString(4,user.getUserTel());
ps.setInt(5,user.getId());
int num=ps.executeUpdate();
return num;
} catch (SQLException e) {
e.printStackTrace();
}finally {
DBUtil.closeAll(rs,ps,con);
}
return 0;
}10.添加新的用户
点击按钮时弹出一个模态框来输入用户信息
/*
添加用户信息
*/
function addUser() {
//获取修改完后得表单重点得值
var userName=$("#username1").val();
var userSex=$("input[name='gender']:checked").val();
var userAge=$("#userage1").val();
var userTel=$("#usertel1").val();
$.ajax({
url:"user",
type:"POST",
data:{
"userName":userName,
"userSex":userSex,
"userAge":userAge,
"userTel":userTel,
"_method":"addUser"
},
dataType:"text",
success:function (data){
if (data=="success"){
$('#myModal1').modal('hide');
showUser();
}
}
});
}controller层
else if (method.equals("addUser")){
addUser(req,resp);
}public void addUser(HttpServletRequest req, HttpServletResponse resp) throws IOException {
req.setCharacterEncoding("utf-8");
String userName = req.getParameter("userName");
String userSex = req.getParameter("userSex");
String userAge = req.getParameter("userAge");
String userTel = req.getParameter("userTel");
User u = new User();
u.setUserSex(userSex);
u.setUserName(userName);
u.setUserAge(userAge);
u.setUserTel(userTel);
String mess = userService.addUser(u);
resp.setContentType("text/html;charset=utf-8");
resp.getWriter().write(mess);
}service层
String addUser(User user);@Override
public String addUser(User user) {
int num = userDao.insertUser(user);
if(num>0){
return "success";
}else {
return "fail";
}
}dao层
int insertUser(User user); @Override
public int insertUser(User user) {
con=DBUtil.getCon();
String sql="insert into user (userName,userSex,userAge,userTel) value (?,?,?,?)";
try {
ps=con.prepareStatement(sql);
ps.setString(1, user.getUserName());
ps.setString(2, user.getUserSex());
ps.setString(3, user.getUserAge());
ps.setString(4, user.getUserTel());
int num=ps.executeUpdate();
return num;
} catch (SQLException e) {
e.printStackTrace();
}finally {
DBUtil.closeAll(rs,ps,con);
}
return 0;
}11.搜索有条件的用户
/*
按照范围查找
*/
function queryUser() {
var username=$("#user_name").val();
var usertel=$("#user_tel").val();
$.ajax({
url:"user",
type:"POST",
data:{
"userName":username,
"userTel":usertel,
"_method":"queryUserByUserNameAndTel"
},
dataType:"json",
success:function (data){
//在显示数据前，先清空表格
$("#tab").html("");
var str = "";
for(var i=0;i<data.length;i++){
str+="<tr><td>"+data[i].userName+"</td><td>"+data[i].userAge+"</td><td>"+data[i].userSex+"</td><td>"+
+data[i].userTel+"</td>"+
"<td><button type='button' class='btn btn-danger' onclick='deleteUser("+data[i].id+")'>删除</button>"+
"<button type='button' class='btn btn-primary' data-toggle='modal' data-target='#myModal' onclick='findUserById("+data[i].id+")'>修改</button></td></tr>";
}
$("#tab").html(str);
}
});
}注意的时在查找前要显示所以的用户信息，点击查找后，页面显示的为查找过后的页面，两个都为空时，查找的是全部数据
controller层
else if (method.equals("queryUserByUserNameAndTel")){
queryUserByUserNameAndTel(req,resp);
}public void queryUserByUserNameAndTel(HttpServletRequest req, HttpServletResponse resp) throws IOException {
String userName = req.getParameter("userName");
String userTel = req.getParameter("userTel");
resp.setContentType("text/html;charset=utf-8");
List<User> users = userService.queryUser(userName,userTel);
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(users);
resp.getWriter().write(json);
}service层
List<User> queryUser(String userName,String userTel); @Override
public List<User> queryUser(String userName, String userTel) {
return Optional.ofNullable(userDao.selectUser(userName,userTel)).orElse(Collections.emptyList());
}dao层
List<User> selectUser(String userName,String userTel);
int selectCountAll(); @Override
public List<User> selectUser(String userName, String userTel) {
con=DBUtil.getCon();
String sql="select * from user where 1=1 ";
List<Object> params = new ArrayList<>();
if (!userName.equals("")){
sql+="and userName=? ";
params.add(userName);
}
if (!userTel.equals("")){
sql+="and userTel=? ";
params.add(userTel);
}
try {
ps=con.prepareStatement(sql);
for (int i = 0; i <params.size(); i++) {
ps.setObject(i+1,params.get(i));
}
rs=ps.executeQuery();
List<User> users = new ArrayList<>();
while (rs.next()){
User user = new User();
user.setId(rs.getInt("id"));
user.setUserName(rs.getString("userName"));
user.setUserAge(rs.getString("userAge"));
user.setUserSex(rs.getString("userSex"));
user.setUserTel(rs.getString("userTel"));
user.setUserPwd(rs.getString("userPwd"));
users.add(user);
}
return users;
} catch (SQLException e) {
e.printStackTrace();
}finally {
DBUtil.closeAll(rs,ps,con);
}
return null;
}
@Override
public int selectCountAll() {
con=DBUtil.getCon();
String sql="select count(*) num from user";
try {
ps=con.prepareStatement(sql);
rs=ps.executeQuery();
if (rs.next()){
int totalCounts = rs.getInt("num");
return totalCounts;
}
} catch (SQLException e) {
e.printStackTrace();
}finally {
DBUtil.closeAll(rs,ps,con);
}
return 0;
}
注意，在查询时sql语句的拼接要用空格符号分割开来
12.总结
经过这次一个简单的sevlet项目来实现增删改查操作，由以下问题需要注意：
1.如何获取前端页面传进来的值
2.下一步实现登录页面的时候，如何与数据库中值进行比较，并实现页面的转发，登录页面如何防止sql注入等问题
3.在用户界面用模板实现界面的美化，和具体功能的实现
4.登陆界面实现动态验证码
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