用Jdbc、Servlet和jsp做一个登录
用Jdbc、Servlet和jsp做一个登录
简单介绍：在mysql里新建一个user表：表结构如下
先新建好各个包：实体模型包（类文件）：po → 数据库访问对象包（接口文件）：dao、 → 业务逻辑包（接口文件）：service、 → 控制层包（servlet文件）：servlet、→ 过滤器（servlet文件）：filter → 前端页面显示层：jsp（jsp建立在WebRoot下面）
以此延伸出来的包有：util包（封装的工具类）、dao.impl包（类文件）、service.impl包（类文件）、test类包（用于测试逻辑业务层的方法）
最好先建立好几个基础包，写入内容后再建立实现类包，不然实现类包会将原来的包覆盖掉。
在实现数据库访问对象之前必须先进行数据库的链接：往WebRoot的Web-INF的lib文件中放入需要用到的jar驱动文件，没有的可以到网上下载；我用的是mysql驱动，
https://jingyan.baidu.com/article/22fe7ced29711e3002617f2c.html
这个路径里有教你如何到mySQL官网里下载驱动的方法，很详细；
如果是用的SqlServer的话，我的另外一篇博文里有sqlserver的下载路径；
为了减少耦合性，数据库采用属性文件的方式来连接数据库,数据库属性文件jdbc.properties
jdbc.properties内容如下：
url中的3306是mysql的端口号，SqlServer的端口号：1433 Oracle的端口号：1521
连接数据库可以看我的另外一篇博文，里面有详细步骤，链接如下：
https://blog.csdn.net/weixin_42271651/article/details/90181918
实际操作步骤简介：
1、在po包中新建实体类User；
2、在dao包中新建数据库访问接口UserDao；
3、在dao.impl包新建UserDaoImpl实现类，实现UserDao接口；
4、在service包中新建业务逻辑接口UserService；
5、在service.impl包中新建UserServiceImpl实现类，实现UserService接口；
6、在servlet包中新建UserServlet；
7、在filter包中新建Fiter过滤器，继承Javax.servlet.Fiter接口；
8、在util包中新建DBUtil工具类；
9、在jsp文件中新建login.jsp的JSP文件
10、在jsp文件中新建main.jsp就JSP文件
文件展示图：
操作步骤详解：
- 在po包中新建实体类User；
package com.xmjlit.po;
public class User {
private Integer id;
private String username;
private String password;
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 getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
- 在dao包中新建数据库访问接口UserDao；
package com.xmjlit.dao;
import java.util.List;
import com.xmjlit.po.User;
public interface UserDao {
public void add(User u);
public void delete(int id);
public void update(User u);
public User selectAll(int id);
public List
}
- 在dao.impl包新建UserDaoImpl实现类，实现UserDao接口；
package com.xmjlit.dao.impl;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.xmjlit.dao.UserDao;
import com.xmjlit.po.User;
import com.xmjlit.util.DBUtil;
public class UserDaoImpl implements UserDao {
private Connection con = null;// 引用的是java.sql类型，不要引错了
private PreparedStatement ps = null;
private ResultSet rs = null;
@Override
public void add(User u) {
String sql = "insert into user(username,password) values(?,?)";// sql语句
con = DBUtil.getConnection();// 调用加载驱动的方法
try {
ps = con.prepareStatement(sql);// 调用Connection中的prepareStatement方法来执行sql语句
ps.setString(1, u.getUsername());
ps.setString(2, u.getPassword());
ps.executeUpdate();
System.out.println(u.getUsername() + "新增成功");
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {// 释放外部资源的代码写在finally块中
DBUtil.close(con, ps, rs);
}
}
@Override
public void delete(int id) {
String sql = "delete from user where id=?";
con = DBUtil.getConnection();
try {
ps = con.prepareStatement(sql);
ps.setInt(1, id);
ps.executeUpdate();
System.out.println("删除成功");
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
DBUtil.close(con, ps, rs);
}
}
@Override
public void update(User u) {
String sql = "update user set username=? where id=? ";
con = DBUtil.getConnection();
try {
ps = con.prepareStatement(sql);
ps.setString(1, u.getUsername());
ps.setInt(2, u.getId());
ps.executeUpdate();
System.out.println("修改成功");
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
DBUtil.close(con, ps, rs);
}
}
@Override
public User selectAll(int id) {
String sql = "select * from user where id=?";
User u = new User();
con = DBUtil.getConnection();
try {
ps = con.prepareStatement(sql);
ps.setInt(1, id);
rs = ps.executeQuery();
while (rs.next()) {
u.setId(rs.getInt("id"));
u.setUsername(rs.getString("username"));
u.setPassword(rs.getString("password"));
}
System.out.println("查询成功" + "id=" + u.getId() + " 用户名："
+ u.getUsername() + " 密码：" + u.getPassword());
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return u;
}
@Override
public List
List
String sql = "select * from user";
con = DBUtil.getConnection();
try {
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
User u = new User();
u.setId(rs.getInt("id"));
u.setUsername(rs.getString("username"));
u.setPassword(rs.getString("password"));
list.add(u);
System.out.println("查询成功" + "id=" + u.getId() + " 用户名："
+ u.getUsername() + " 密码：" + u.getPassword());
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;
}
}
- 在service包中新建业务逻辑接口UserService；
package com.xmjlit.service;
import java.util.List;
import com.xmjlit.po.User;
public interface UserService {
public void add(User u);
public void delete(int id);
public void update(User u);
public User selectAll(int id);
public List
}
5、在service.impl包中新建UserServiceImpl实现类，实现UserService接口；
package com.xmjlit.service.impl;
import java.util.List;
import com.xmjlit.dao.impl.UserDaoImpl;
import com.xmjlit.po.User;
import com.xmjlit.service.UserService;
public class UserServiceImpl implements UserService {
private UserDaoImpl userDao=new UserDaoImpl();
@Override
public void add(User u) {
userDao.add(u);
}
@Override
public void delete(int id) {
userDao.delete(id);
}
@Override
public void update(User u) {
userDao.update(u);
}
@Override
public User selectAll(int id) {
User u=userDao.selectAll(id);
return u;
}
@Override
public List
List
return list;
}
}
6、在servlet包中新建UserServlet；
package com.xmjlit.servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.xmjlit.dao.impl.UserDaoImpl;
import com.xmjlit.po.User;
public class UserServlet extends HttpServlet {
public UserDaoImpl ud = new UserDaoImpl();
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
List
request.setAttribute("users", list);
request.getRequestDispatcher("/jsp/main.jsp")
.forward(request, response);
}
}
7、在filter包中新建Fiter过滤器，继承Javax.servlet.Fiter接口；
package com.xmjlit.filter;
import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class Filter extends HttpServlet implements javax.servlet.Filter {
@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req=(HttpServletRequest) request;
HttpServletResponse resp=(HttpServletResponse) response;
StringBuffer path=req.getRequestURL();//利用StingBuffer来分割字符串
System.out.println(path);
String s=path.substring(path.lastIndexOf("/")+1);
//lastIndexOf()：返回指定字符在此字符串中最后一次出现处的索引。
//substring(start index):从指定位置开始截取字符串,默认到末尾。
System.out.println(s);
if ("/jsp/login.jsp".equals(s)||"/servlet/UserServlet".equals(s)) {
chain.doFilter(req, resp);
}
Object u=req.getSession().getAttribute("username");
System.out.println(u);
if (u==null) {
resp.sendRedirect("/jsp/login.jsp");
return;
}
chain.doFilter(req, resp);
}
@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub
}
}
8、在util包中新建DBUtil工具类；
DBUtil思路备注：加载驱动类、获取数据库连接、获取PreparedStatement、执行query/update 、关闭con/st/rs
package com.xmjlit.util;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
public class DBUtil {
// 为加载驱动准备的四个参数
private static String user = null;
private static String password = null;
private static String url = null;
private static String driver = null;
static {
Properties pro = new Properties();
// 读取文件数据
InputStream in = DBUtil.class.getClassLoader().getResourceAsStream(
"jdbc.properties");
try {
pro.load(in);// 加载流
user = pro.getProperty("user");// 获取流里的数据，引号里的user是jdbc.properties文件中的user
password = pro.getProperty("password");
url = pro.getProperty("url");
driver = pro.getProperty("driver");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static Connection getConnection() {
Connection con = null;
try {
Class.forName(driver);
con = DriverManager.getConnection(url, user, password);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return con;
}
public static void close(Connection con, PreparedStatement ps, ResultSet rs) {// 关闭con// ps // rs
try {
if (con != null) {
con.close();
}
if (ps != null) {
ps.close();
}
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
9、在jsp文件中新建login.jsp的JSP文件
<%@ page language="java" import="java.util.*" pageEncoding="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">
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<c:set value="${pageContext.request.contextPath}" scope="page" var="ctx">c:set>
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'login.jsp' starting pagetitle>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
head>
<body>
<form action="${ctx}/servlet/UserServlet" method="post">
<input style="display: none;" name="type" value="login"> 用户名<input
id="username" name="username" value=""> 密码<input
id="password" name="password" value=""> <input type="submit"
value="登录"><input type="reset" value="取消">
form>
body>
html>
10、在jsp文件中新建main.jsp就JSP文件
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<c:set value="${pageContext.request.contextPath}" scope="page" var="ctx">c:set>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'main.jsp' starting pagetitle>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
head>
<body>
<table width="90%" border="1" cellpadding="0" cellspacing="0">
<tr>
<td width="5%" class="td_title">用户idtd>
<td width="5%" class="td_title">用户名td>
<td width="5%" class="td_title">密码td>
<td width="5%" class="td_title">新增td>
<td width="5%" class="td_title">修改td>
<td width="5%" class="td_title">删除td>
tr>
<c:forEach items="${users}" varStatus="status" var="user">
<tr>
<td width="5%" class="td_title">${status.index+1}td>
<td width="5%" class="td_title">${user.username}td>
<td width="5%" class="td_title">${user.password}td>
<td width="5%" class="td_title"><a
href="${ctx}/servlet/ListServlet?type=addJump">新增a>td>
<td width="5%" class="td_title"><a
href="${ctx}/servlet/ListServlet?type=updateJump&id=${user.id}">修改 a>
td>
<td width="5%" class="td_title"><a
href="${ctx}/servlet/ListServlet?type=delete&id=${user.id}"> 删除 a>td>
tr>
c:forEach>
body>
html>
登录页面效果图展示：
登录成功后效果图：
