JavaWeb连接数据库增删改查（含登录验证、分页）
简单的页面对数据库的增删改查——新手入门推举
一、准备工作
- eclipse(无版本要求)或myeclipse都行，本人用的是eclipse
- Apache Tomcat，我用的是7.0版本
- 数据库 MySQL
- 需要掌握到的知识点：项目的基本框架搭建（经典三层框架）
二、项目的基本框架搭建
三层框架分别为：表现层、业务逻辑层、数据访问层。
- 表现层：包含JSP和Servlet等与web相关的内容，负责与浏览器的响应和请求；
- 业务层：只关心业务逻辑；
- 数据层：封装了对数据库的访问细节，数据操作类；
三层关系：表现层依赖业务层，而业务层依赖数据层
三、实现数据库的连接
需要在MySQL中创建所需数据库，并将表建好。
- 数据库名为test
- 项目信息表名为User，表结构如下，其中id为自增长主键，增量为1。
四、代码实现
1、在Util包下新建一个JDBCUtil 类用来处理对数据进行连接
package Util;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;
public class JDBCUtil {
private static String DBDriver="org.gjt.mm.mysql.Driver";
private static String url="jdbc:mysql://localhost:3306/test?characterEncoding=UTF-8";
private static String user="root";
private static String password="root";
static Connection con=null;
static Statement sta=null;
static PreparedStatement psta=null;
//获得数据库的链接
public static Connection getConnection()
{
try {
Class.forName(DBDriver);
try {
con = DriverManager.getConnection(url, user, password);
return con;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (ClassNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
return null;
}
public static Statement createStatement()
{
try {
sta=getConnection().createStatement();
return sta;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
//创造数据预处理对象
public static PreparedStatement createPreparedStatement(String sql)
{
try {
psta = getConnection().prepareStatement(sql);
return psta;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return psta;
}
//关闭所有打开的资源
public static void closeOperation()
{
if(psta==null)
{
try {
psta.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(sta==null)
{
try {
sta.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(con==null)
{
try {
con.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
2、在Model包下创建User实体类（实体类中的对象对应数据库表中的字段数据）
package Model;
//类的设计
public class User {
private int id;
private String userName;
private String password;
private String Email;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getEmail() {
return Email;
}
public void setEmail(String email) {
Email = email;
}
}
3、在Dao包下创建UserDao实现对数据库的增删改查方法
package Dao;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import Model.User;
import Util.MysqlHelper;
public class UserDao {
public boolean Login(String userName,String password){
String sql="select userName,password from User ";
ResultSet rs=MysqlHelper.executeQuery(sql);
try {
while(rs.next()){ //用户输入的信息和数据库中的信息做比较，判断输入是否正确；
String name = rs.getString("userName");
String pwd = rs.getString("password");
if(name.equals(userName) && pwd.equals(Util.MD5Helper.GetMD5Code(password))){
return true;
}
}
rs.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return false;
}
public void addUser(User u)
{
String sql="insert into User (userName,password,Email) values (?,?,?)";
Util.MysqlHelper.executeUpdate(sql, u.getUserName(),Util.MD5Helper.GetMD5Code(u.getPassword()),u.getEmail());
}
public void deleteUser(int i){
String sql = "delete from user where id=?";
Util.MysqlHelper.executeUpdate(sql,i);
}
public void modifyUser(User u){
String sql = "update User set id=?,userName=?,Email=? where id=? ";
Util.MysqlHelper.executeUpdate(sql,u.getId(),u.getUserName(),u.getEmail(),u.getId());
}
public void deleteUserByUserName(String userName)
{
}
public void updateUser(Object...objects)
{
}
//根据用户名查询到一个User对象，然后返回User对象
public User QueryUserByUserName(String userName)
{
User u=new User();
String sql="select * from User where userName=?";
ResultSet rs=MysqlHelper.executeQuery(sql, userName);
try {
if(rs.next())
{
u.setId(Integer.parseInt(rs.getObject("id").toString()));
u.setUserName(rs.getString("userName"));
u.setEmail(rs.getString("Email"));
}
} catch (NumberFormatException | SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return u;
}
//查询所有用户信息
public List QueryUsers()
{
List list=new ArrayList(); //最终返回整个list集合
String sql="select * from user";
ResultSet rs=MysqlHelper.executeQuery(sql);
try {
while(rs.next())
{
//保存取出来的每一条记录
User u=new User();
u.setId(rs.getInt("id"));
u.setUserName(rs.getString("userName"));
u.setEmail(rs.getString("Email"));
list.add(u);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;
}
}
4、在Util包下创建MysqlHelper接收传递过来的参数
package Util;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class MysqlHelper {
//执行增、删、改 用可变参数，来接收传递过来的参数，参数的个数可以不确定，提高使用率
public static int executeUpdate(String sql,Object...objects)
{
int len=0;
PreparedStatement psta=JDBCUtil.createPreparedStatement(sql);
try {
for (int i = 0; i < objects.length; i++) {
psta.setObject(i+1, objects[i]);
}
len=psta.executeUpdate();
return len;
//逐个对objects数组中的元素来进行设置 ,数组中一个元素对应一个问号
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return len;
}
//执行查询
public static ResultSet executeQuery(String sql,Object...objects)
{
ResultSet rs=null;
PreparedStatement psta=JDBCUtil.createPreparedStatement(sql);
try{
for (int i = 0; i < objects.length; i++) {
psta.setObject(i+1, objects[i]);
}
rs=psta.executeQuery();
return rs;
}catch(SQLException e)
{
e.printStackTrace();
}finally{
//JDBCUtil.closeOperation();
}
return rs;
}
}
5、在BLL包下创建UserBLL传递参数调用增、删、改、查方法
package BLL;
import java.util.List;
import Dao.UserDao;
import Model.User;
public class UserBLL {
public void addUser(User u) {
UserDao userdao = new UserDao();
userdao.addUser(u);
}
public boolean Login(String userName,String password){
return new UserDao().Login(userName,password);
}
public void deleteUser(int i) {
UserDao userdao = new UserDao();
userdao.deleteUser(i);
}
public void modifyUser(User u) {
UserDao userdao = new UserDao();
userdao.modifyUser(u);
}
// 根据用户名查询到一个User对象，然后返回User对象
public User QueryUserByUserName(String userName) {
return new UserDao().QueryUserByUserName(userName);
}
public List QueryUsers() {
return new UserDao().QueryUsers();
}
}
6、在cn.UI包下创建Login用于登录验证
package cn.UI;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import Model.User;
public class Login extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("gbk");
response.setCharacterEncoding("gbk");
String userName=request.getParameter("userName");
String passWord=request.getParameter("passWord");
if(new BLL.UserBLL().Login(userName, passWord)){
response.sendRedirect("show");
}
PrintWriter pw=response.getWriter();
pw.println("账户或密码错误！");
pw.flush();
pw.close();
}
}
7、创建分页查询类
package cn.UI;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import Model.User;
public class ShowData extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
List list=new BLL.UserBLL().QueryUsers();
String pageIndex1=request.getParameter("pageIndex");
if(pageIndex1==null){
pageIndex1="0";
}
int pageIndex=Integer.parseInt(pageIndex1); //拿到传递过来的请求的第几条记录
response.setCharacterEncoding("gbk");
PrintWriter pw=response.getWriter();
StringBuilder sb=new StringBuilder(); //字符串的缓存区
//int pageIndex=0; //这是第几页
int pageSize=3; //就是每一页要显示的数据总记录数
for(int j=0;j"+(j+1)+" ");
}
for(int i=pageIndex*pageSize;i<(pageIndex+1)*pageSize;i++){
User u=(User)list.get(i);
sb.append("");
sb.append("用户编号"+u.getId()+" ");
sb.append(String.format("用户名%s ", u.getUserName()));
sb.append("邮箱"+u.getEmail()+" ");
sb.append("增加 ");
sb.append("删除 ");
sb.append("修改 ");
sb.append("
");
pw.write(sb.toString());
pw.flush();
pw.close();
}
}
8、增加类
package cn.UI;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import Model.User;
public class AddUser extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String userName=request.getParameter("userName");
String passWord=request.getParameter("passWord");
String Email=request.getParameter("Email");
User u=new User();
u.setUserName(userName);
u.setPassword(passWord);
u.setEmail(Email);
new BLL.UserBLL().addUser(u);
response.sendRedirect("show");
}
}
9、删除类
package cn.UI;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class DeleteServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding("gbk");
response.setCharacterEncoding("gbk");
PrintWriter pw=response.getWriter();
new BLL.UserBLL().deleteUser(Integer.parseInt(request.getParameter("id")));
response.sendRedirect("show");
pw.flush();
pw.close();
}
}
10、修改类一，获取当前用户数据值，便于操作者修改
package cn.UI;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import Model.User;
public class ModifyData extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setCharacterEncoding("gbk");
String userName=request.getParameter("userName"); //拿到要查询的id编号的数据
User u=new BLL.UserBLL().QueryUserByUserName(userName);
//展示u的数据，并显示出来
//读模板，然后替换特殊字符部分
BufferedReader br=new BufferedReader(new FileReader("E:\\Eclipse工作空间\\第二部\\ServiceJava\\WebContent\\modifyData.html"));
String s=br.readLine();
String context="";
while(s!=null)
{
context=context+s;
s=br.readLine();//读出所有的文本
}
context=context.replace("@Id", u.getId()+""); //替换字符串
context=context.replace("@userName", u.getUserName()).replace("@Email", u.getEmail());
PrintWriter pw=response.getWriter();
pw.println(context);
pw.flush();
pw.close();
}
}
11、修改类二
package cn.UI;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import Model.User;
public class UpdateData extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
User u=new User();
request.setCharacterEncoding("gbk");
response.setCharacterEncoding("gbk");
int id=Integer.valueOf(request.getParameter("id"));
String userName=request.getParameter("userName");
String Email=request.getParameter("Email");
u.setId(id);
u.setUserName(userName);
u.setEmail(Email);
new BLL.UserBLL().modifyUser(u);
response.sendRedirect("show");
}
}
PS：我这里加了一个MD5，加密了用户密码（可用可不用）
package Util;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class MD5Helper {
private static String bytesToHex(byte[] bytes) {
StringBuffer md5str = new StringBuffer();
//把数组每一字节换成16进制连成md5字符串
int digital;
for (int i = 0; i < bytes.length; i++) {
digital = bytes[i];
if(digital < 0) {
digital += 256;
}
if(digital < 16){
md5str.append("0");
}
md5str.append(Integer.toHexString(digital));
}
return md5str.toString().toLowerCase();
}
public static String GetMD5Code(String strObj) {
String resultString = null;
try {
resultString = new String(strObj);
MessageDigest md = MessageDigest.getInstance("MD5");
// md.digest() 该函数返回值为存放哈希值结果的byte数组
byte b[]=md.digest(strObj.getBytes());
resultString =bytesToHex(b) ;
} catch (NoSuchAlgorithmException ex) {
ex.printStackTrace();
}
return resultString;
}
}
五、Web的配置
ServiceJava
login.html
login.htm
login.jsp
index.html
index.htm
index.jsp
default.html
default.htm
default.jsp
ShowData
cn.UI.ShowData
ShowData
/show
AddUser
cn.UI.AddUser
AddUser
/addUser
Login
cn.UI.Login
Login
/login
DeleteServelet
cn.UI.DeleteServlet
DeleteServelet
/delete1
modifyData
cn.UI.ModifyData
modifyData
/modifyData
UpdateData
cn.UI.UpdateData
UpdateData
/upDate
六、HTML页面代码部分
1、增
Insert title here
2、删
Insert title here
3、改
Insert title here
4、登录
Insert title here
注意：
编码格式需要统一，否则会出现乱码情况，查询修改等功能也可能报错