我的第一个JDBC小项目
2024-05-15 15:41:38
我的第一个JDBC小项目
引言：以下都是个人学习中的一些总结，本人能力有限，其中存在很多错误与不足，还请阅读者斧正。！并非教程！！并非教程！！并非教程！
JDBC是Java DataBase Connectivity的简称，在我理解看来，它就是Java配合DB用来实现客户增删改查的需求的工具。
JDBC的五个步骤：
1.加载JDBC驱动Class.forName(“com.mysql.jdbc.Driver”);
2.与数据库建立连接DriverManager.getConnection(url,uname,pwd);
3.获取操作对象，发送sql语句得到返回结果
4.处理返回结果
5.释放资源.close()
————————————————
版权声明：本文为CSDN博主「CHANGEXCX」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/CHANGEXCX/article/details/80399626
一、项目需求
1.完成数据从前端（页面）成功添加数据到后台数据库中（增）
2.实现数据从前端（页面）成功删除后台数据库中的数据（删）
3.完成数据从前端（页面）成功修改数据并在后台数据库中显示（改）
4.实现从前端（页面）成功查看后台数据库中所有数据（查）
二、构建项目大概框架(MVC)
1.后台数据库(Model)
2.前端JSP块(View)
3.Java代码实现块(Controller)
三、具体实施步骤
1.数据库
1.1建立数据库，创建数据表
2.Java
2.1创建好相应的包与文件夹
2.2编写User包中的User.class
package User;
public class User{private int id;private String uname;private String up;private String sex;public void setId(int id) {this.id= id;}public int getId() {return id;}public void setUname(String uname) {this.uname=uname;}public String getUname() {return uname;}public void setUp(String up) {this.up=up;}public String getUp() {return up;}public void setSex(String sex) {this.sex=sex;}public String getSex() {return sex;}public String toString() {return "User[id="+id+",uname="+uname+",up="+up+",sex="+sex+"]";}
}
2.3架包：mysql-connector-java
没有这个包Java和数据库就不能连接
2.4编写DB包中的有关数据库的一系列操作的DB.class
package DB;
import User.User;
import java.sql.*;
import java.util.ArrayList;
public class DB{private Connection conn = null;//连接对象private PreparedStatement pstmt = null;//执行sql语句对象private ResultSet rs= null;//装载查询结果集//=================数据库连接=======================public Connection getConnection() {Connection con = null;try {Class.forName("com.mysql.jdbc.Driver");//加载驱动con=(Connection)DriverManager.getConnection("jdbc:mysql://localhost:3306/testttt?useUnicode=true&characterEncoding=utf-8&useSSL=false","root","root");//与数据库建立连接DriverManager.getConnection(url,uname,pwd);}catch(Exception e){e.printStackTrace();System.out.println("数据库连接失败");}return con;}//=================关闭=======================public void releaseDB(ResultSet rs,PreparedStatement pstmt,Connection conn) {if(rs!=null) {try {rs.close();}catch(SQLException e) {e.printStackTrace();}}if(pstmt!=null) {try {pstmt.close();}catch(SQLException e) {e.printStackTrace();}}if(conn!=null) {try {conn.close();}catch(SQLException e){e.printStackTrace();}}}//====================添加用户数据===================public boolean add(User user) {conn=getConnection();//连接数据库try {String sql = "insert into test (uname,up,sex) values(?,?,?)";//sql插入语句pstmt=conn.prepareStatement(sql);//创建一个 PreparedStatement 对象来将参数化的 SQL 语句发送到数据库pstmt.setString(1,user.getUname());//将页面端获取到的用户填入的数据覆盖数据库中原始数据(ps:“1”指第一个问号)pstmt.setString(2, user.getUp());pstmt.setString(3,user.getSex());pstmt.executeUpdate();//此方法用于执行sql语句，返回值为受影响的行数（更新计数），int类型pstmt.close();//关闭return true;}catch(SQLException e) {e.printStackTrace();return false;}}//====================根据id删除用户数据===================public boolean delete(int id) {conn = getConnection();try {String sql = "delete from test where id="+id;//sql删除语句pstmt=conn.prepareStatement(sql);pstmt.executeUpdate();pstmt.close();return true;}catch(SQLException e) {e.printStackTrace();return false;}}//====================根据ID修改用户数据===================public boolean update(User user,int id) {conn = getConnection();try {String sql = "update test set uname=?,up=?,sex=? where id=?";//sql修改语句pstmt = conn.prepareStatement(sql);pstmt.setString(1,user.getUname());pstmt.setString(2,user.getUp());pstmt.setString(3,user.getSex());pstmt.setInt(4,id);//此ID是需要修改的用户IDpstmt.executeUpdate();pstmt.close();}catch(SQLException e) {e.printStackTrace();return false;}return true;} //====================查看所有用户的数据===================public ArrayList<User> Query(){conn = getConnection();ArrayList<User> list = new ArrayList<User>();//用于存储**对象**。与数组不同，数组一旦创建，长度固定，但是ArrayList的长度是动态的，不受限制，可以存储任意多的对象try {String sql = "select * from test";//sql查询语句pstmt=conn.prepareStatement(sql);rs=pstmt.executeQuery();//此方法用于下达select指令，以查询数据库，它会把数据库响应的查询结果存放在ResultSet类对象中供我们使用while(rs.next()) {//rs是结果集。查询出的记录是一个列表，初始时指针指向的是第一条记录之前的。每rs.next()一次指针都会向后移动一位，指向下一条记录。User user = new User();user.setId(rs.getInt("id"));user.setUname(rs.getString("uname"));user.setUp(rs.getString("up"));user.setSex(rs.getString("sex"));list.add(user);//将每次查询的user对象放到list中储存}}catch(SQLException e) {e.printStackTrace();System.out.println("查询失败");}return list;}//====================根据id查看其中一个用户的数据===================//原理同上public ArrayList<User> QueryOne(int id){conn=getConnection();ArrayList<User> list =new ArrayList<User>();try {String sql = "select * from test where id="+id;pstmt=conn.prepareStatement(sql);rs=pstmt.executeQuery();while(rs.next()) {User user = new User();user.setId(rs.getInt("id"));user.setUname(rs.getString("uname"));user.setUp(rs.getString("up"));user.setSex(rs.getString("sex"));list.add(user);}}catch(SQLException e) {e.printStackTrace();System.out.println("查询失败");}return list;}//================根据uname，up登陆============================public boolean Login(String uname ,String up){conn=getConnection();boolean flag = false;try{String sql ="select * from test where uname=? and up=?";pstmt=conn.prepareStatement(sql);pstmt.setString(1,uname);pstmt.setString(2,up);rs=pstmt.executeQuery();if(rs.next()){flag = ture;}}catch(SQLException e){e.printStackTrace();}return flag;}//====================测试====================================public static void main(String[] args) {DB db = new DB();User user = new User();user.setUname("a");user.setUp("a");user.setSex("a");db.add(user);System.out.println(db.update(user, 8));;};
}
3.JSP
3.1建立几个必要的JSP前端页面
显示用户信息的主页面：Manage.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8" import = "DB.DB"import = "User.User"import = "java.util.ArrayList"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %><!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>管理用户界面</title>
</head>
<body><table align="center" border="1" width="800" >
<tr>
<td align="center" colspan="8">用户管理界面</td>
</tr>
<tr>
<td>id</td>
<td>用户名</td>
<td>密码</td>
<td>性别</td>
<td>删除</td>
<td>修改</td>
<td>查看</td>
</tr>
<%ArrayList<User> list =(ArrayList<User>)request.getAttribute("list");for(User user:list){ %>
<tr><!--request.getAttribute需要返回对象时要强制转换,foreach遍历 -->
<td><%=user.getId()%></td>
<td><%=user.getUname() %></td>
<td><%=user.getUp() %></td>
<td><%=user.getSex() %></td>
<td><a href="<%=basePath %>/controller?id=<%=user.getId()%>&action=delete">删除</a></td>
<td><a href="<%=basePath %>/controller?id=<%=user.getId()%>&action=update">修改</a></td>
<td><a href="<%=basePath %>/controller?id=<%=user.getId()%>&action=detail">查看</a></td>
<td><a href="<%=basePath %>/register.jsp">添加</a></td></tr>
<%} %></table></body>
</html>
注册(添加信息）页面，register.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>注册</title>
</head>
<body>
<form action="add" method="post">
用户名:<input type="text" name = uname><br>
密码<input type = "password" name = up><br>
<input type="radio" name=sex value="male">男<input type="radio" name= sex value="female">女<br>
<input type ="submit" value = "注册"> <br></form>
</body>
</html>
查看个人信息，index.jsp
(请无视菜鸟的乱码）
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"import ="DB.DB"import ="User.User"import = "java.util.ArrayList"
%><!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>查看个人信息</title>
</head>
<body>
<table align="center" border="1">
<tr>
<td>id</td>
<td>用户名</td>
<td>密码</td>
<td>性别</td>
</tr><%ArrayList<User> list =(ArrayList<User>)request.getAttribute("usermessagall") ;for(User user:list){%>
<tr>
<td><%=user.getId() %></td>
<td><%=user.getUname() %></td>
<td><%=user.getUp() %></td>
<td><%=user.getSex() %></td>
</tr>
<%} %>
</table>
</body>
</html>
修改数据，update.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"import ="java.util.ArrayList"import ="User.User"import ="DB.DB"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>修改信息</title>
</head>
<body>
<form action="update" method="post">
<%int id=Integer.parseInt(request.getParameter("id"));
session.setAttribute("id",id);%>
<%ArrayList<User> list= (ArrayList<User>)request.getAttribute("list");for(User user:list){%><br>
Username:<input type="text" name = "uname" value ="<%=user.getUname()%>" ><br>
Password<input type = "text" name ="up" value="<%=user.getUp()%>"><br>
<%if(user.getSex().equals("male")){ %>
<input type="radio" name="sex" value="male" checked="male">Male
<input type="radio" name= "sex" value="female">Female<br>
<%}else{ %>
<input type="radio" name="sex" value="male" >Male
<input type="radio" name= "sex" value="female" checked="female">Female<br>
<% }}%>
<%-- <%=request.getParameter("id") %>
<%request.getParameter("id");request.setAttribute("id",id) ;%> --%><input type ="submit" value = "Update"> <br></form>
</body>
</html>
登陆,login.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登陆</title>
</head>
<body>
<form action="login" method="post">
用户名:<input type="text" name = uname><br>
密码<input type = "password" name = up><br>
<input type="submit" value="登陆">
</form>
</body>
</html>
4.Servlet**（以下文件均为servlet）
servlet在我的项目中是非常重要的一环，它主要负责处理客户请求与业务处理（中间角色）
创建h.java，作用：把查询结果转发到Manage.jsp
package Servlet;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import DB.DB;
import User.User;
import java.sql.*;
import java.util.ArrayList;/*** Servlet implementation class h*/
public class h extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public h() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse* response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// TODO Auto-generated method stubDB db = new DB();ArrayList<User> list = db.Query();//查询“所有数据”，并把“所有数据”放到list中request.setAttribute("list", list);//servlet传递参数到jsp用setAttribute（）方法request.getRequestDispatcher("/Manage.jsp").forward(request, response);//转发：地址不变，可以用request对象传递参数，“”中带/}/*** @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);}}创建add.java，作用：添加用户
package Servlet;import java.io.PrintWriter;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import DB.DB;
import User.User;/*** Servlet implementation class add*/
public class add extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public add() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 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 stubdoGet(request, response);User user = new User();PrintWriter out = response.getWriter();String uname=request.getParameter("uname");//以form表单和url从jsp传到servlet的参数，可以用getParameter（）方法获取String up = request.getParameter("up");String sex = request.getParameter("sex");user.setUname(uname);user.setUp(up);user.setSex(sex);DB db = new DB();if(db.add(user)) {out.print("<script language=javascript>alert('Add Success');window.location.href='/JspDemo/h';</script>");}else {out.print("<script language=javascript>alert('Add failure');window.location.href='/JspDemo/register.jsp';</script>");}
// out.print(uname);
// out.print(up);
// out.print(sex);}}创建controller.java，作用：对用户发送的请求做出响应
package Servlet;import java.io.PrintWriter;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import DB.DB;
import User.User;
import java.sql.*;
import java.util.ArrayList;/*** Servlet implementation class controller*/
public class controller extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public controller() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse* response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// TODO Auto-generated method stubPrintWriter out = response.getWriter();response.setCharacterEncoding("UTF-8");int id = Integer.parseInt(request.getParameter("id"));//获取id，注意：request.getParameter()所取到的都是默认字符串类型，需要类型转换。String action = request.getParameter("action");DB db = new DB();User user = new User();if (action.equals("detail")) {ArrayList<User> list = db.QueryOne(id);request.setAttribute("usermessagall", list);request.getRequestDispatcher("/index.jsp").forward(request, response);}if (action.equals("delete")) {if (db.delete(id)) {out.println("<script language=javascript>alert('Delete Success');window.location.href='/JspDemo/h';</script>");} else {out.println("<script language=javascript>alert('Delete Failure');window.location.href='/JspDemo/h';</script>");}}if (action.equals("update")) {ArrayList<User> list = db.QueryOne(id);request.setAttribute("list", list);request.getRequestDispatcher("/update.jsp").forward(request, response);}}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse* response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// TODO Auto-generated method stubdoGet(request, response);}}建立update.java，作用用于响应客户端的修改信息请求（本来应该放在controller里，后期再完善，明天考教资没时间了）
package Servlet;
import java.io.PrintWriter;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import DB.DB;
import User.User;/*** Servlet implementation class update*/
public class update extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public update() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 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 stubdoGet(request, response);PrintWriter out = response.getWriter();//在servlet中用session方法只能request.getSession().getAttribute()，此时获得到的是对象，需先转为String型，再转为Int型int id = Integer.parseInt((request.getSession().getAttribute("id").toString()));String uname = request.getParameter("uname");//获取客户端输入的数据String up = request.getParameter("up");String sex = request.getParameter("sex");
// out.print(uname);
// out.print(up);
// out.print(sex);User user = new User();user.setUname(uname);user.setUp(up);user.setSex(sex);
// DB db = new DB();
// out.print(id);if(db.update(user, id)) {out.print("<script language=javascript>alert('Update Success');window.location.href='/JspDemo/h';</script>");}else {out.print("<script language=javascript>alert('Update Failure');window.location.href='/JspDemo/update.jsp';</script>");}}}创建login.java，作用：实现登录功能。
package Servlet;
import java.io.PrintWriter;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;
import DB.DB;
import User.User;
/*** Servlet implementation class login*/
public class login extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public login() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubresponse.getWriter().append("Served at: ").append(request.getContextPath());}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubUser user = new User();PrintWriter out = response.getWriter();String uname = request.getParameter("uname");String up = request.getParameter("up");
// user.setUname(uname);
// user.setUp(up);DB db = new DB();if(db.Login(uname, up)) {out.println("<script language=javascript>alert('Login Success');window.location.href='/JspDemo/loginSuccess.jsp';</script>");}else {out.println("<script language=javascript>alert('Login failure');window.location.href='/JspDemo/login.jsp';</script>");}}}四、功能展示
原始界面：
1.添加
2.删除：
删除id28
3.修改
修改id27
4.查看
查看id27
5.登陆
登陆成功
登陆失败
五、学习笔记
1.业务逻辑
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2.关于JSP与Servlet之间的传参问题
2.1JSP
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