需求：
登录功能
登录页面输入用户名和密码， 到数据库进行验证 ，如果成功跳转到success.html页面，失败跳转到error.html页面
数据库 mysql，数据表 t_user表【表中的字段 ：name 用户名，pwd 密码】
实现：
mysql 存储数据建表
jdbc操作java代码连接查询数据库里对应的字段
servlet将 html和java连接起来，用login来登录转发到成功或者失败页面。
实现步骤：
jdbc
依赖 jar包，数据库连接的util DBUtil数据库连接工具类
mysql 连接
db.properties 数据库连接配置
核心代码实现：（DAO层）
sql语句 查询：String sql = "select * from t_user where name=? and pwd =? ";
创建一个实体类和数据库表对应，dao层 用户名和密码验证，返回一个结果 对象
servlet调用DAO层：如果用户存在 ，不为空，跳转到ok.html页面 ；如果不存在，对象为空， 登录失败 error.html
前台页面：
login.html【登录界面】
<!DOCTYPE html>
<html>
<head>
<title>login.html</title>
<meta charset="utf-8">
<meta name="keywords" content="keyword1,keyword2,keyword3">
<meta name="description" content="this is my page">
<meta name="content-type" content="text/html; charset=UTF-8"> <!--<link rel="stylesheet" type="text/css" href="./styles.css">--> </head> <body>
<form action="UserLogin">
用户名：<input type="text" name="uname" id="uname" /><br>
密码：<input type="password" name="pwd" id="pwd" /><br>
<input value="登录" type="submit"/>
</form>
</body>
</html>
success.html【登录成功界面】
<!DOCTYPE html>
<html>
<head>
<title>success.html</title>
<meta charset="utf-8">
<meta name="keywords" content="keyword1,keyword2,keyword3">
<meta name="description" content="this is my page">
<meta name="content-type" content="text/html; charset=UTF-8"> <!--<link rel="stylesheet" type="text/css" href="./styles.css">--> </head> <body>
This is 登录成功 page.看到女神<br>
<div>
<img src="imges/success.jpg" width="800px" height="500px"/>
</div>
</body>
</html>
error.html【登录失败界面】
<!DOCTYPE html>
<html>
<head>
<title>error.html</title>
<meta charset="utf-8">
<meta name="keywords" content="keyword1,keyword2,keyword3">
<meta name="description" content="this is my page">
<meta name="content-type" content="text/html; charset=UTF-8"> <!--<link rel="stylesheet" type="text/css" href="./styles.css">--> </head> <body>
This is 登录失败 page.一直在转悠转悠 <br>
<div>
<img src="imges/error.gif" />
</div>
</body>
</html>
entity层【实体类】
package boom.servlet.entity;
/**
* 实体类
* @author Administrator
*
*/
public class T_user {
// 对应着数据库表的字段
private int id;
private String name;
private String pwd;
// 无参构造方法
public T_user() {
}
// 有参构造方法
public T_user(int id, String name, String pwd) {
super();
this.id = id;
this.name = name;
this.pwd = pwd;
}
// getter setter
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
// 重写toString
@Override
public String toString() {
return "T_user [id=" + id + ", name=" + name + ", pwd=" + pwd + "]";
} }
util层【封装的JDBC数据库连接】
package boom.servlet.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.sql.Statement;
import java.util.Properties;
/**
* 连接数据库的工具类
* @author Administrator
*
*/
public class DBUtil {
private static String driver;
private static String url;
private static String username;
private static String password; static {
// 创建properties对象获取属性文件的内容
Properties p = new Properties();
// 获取属性配置文件的读取流对象
InputStream is = DBUtil.class.getResourceAsStream("/db.properties");
try {
// 加载属性配置文件
p.load(is);
// 获取jdbc参数
driver = p.getProperty("driver");
url = p.getProperty("url");
username = p.getProperty("username");
password = p.getProperty("password");
// 加载驱动
Class.forName(driver);
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} // 获取Connection对象
public static Connection getConnection() {
Connection conn = null;
try {
conn = DriverManager.getConnection(url, username, password);
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
} // 封装获取PreparedStatement对象
public static PreparedStatement getPreparedStatement(String sql,
Connection conn) { PreparedStatement ps = null;
try {
ps = conn.prepareStatement(sql);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return ps; } // 封装获取Statement对象
public static Statement getStatement(Connection conn) {
Statement stmt = null;
try {
stmt = conn.createStatement();
} catch (SQLException e) {
e.printStackTrace();
}
return stmt; } // 关闭资源
//父类可以调用 子类继承过的父类方法
public static void closeAll(ResultSet rs, Statement ps, Connection conn) {
try {
if(rs!=null ){
rs.close();
}
} catch (SQLException e1) {
e1.printStackTrace();
}
try {
if(ps!=null ){
ps.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
try {
if(conn!=null){
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
// 封装DML
public static int executeDML(String sql, Object... objs) {
// 创建连接对象
Connection conn = getConnection();
// 创建sql命令对象
PreparedStatement ps = DBUtil.getPreparedStatement(sql, conn);
// 给占位符赋值
try {
conn.setAutoCommit(false);
for (int i = 0; i < objs.length; i++) {
ps.setObject(i + 1, objs[i]);
}
int i = ps.executeUpdate();
conn.commit();
return i;
} catch (Exception e) {
try {
conn.rollback();
} catch (SQLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
} finally {
// 关闭资源
DBUtil.closeAll(null, ps, conn);
}
// 返回结果
return -1;
}
// 测试数据库是否连接成功
public static void main(String[] args) {
Connection conn = DBUtil.getConnection();
System.out.println(conn);
}
}
dao层【user实现类】
package boom.servlet.dao; import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException; import boom.servlet.entity.T_user;
import boom.servlet.util.DBUtil; /**
* 登录查询实现类
* @author Administrator
*select * from t_user where name='admin' and pwd='admin'
*/
public class UserDaoImpl {
// 返回对象
public T_user getUser(String name,String pwd){
String sql = "select * from t_user where name=? and pwd =? ";
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
T_user user= null;
//1.创建连接
conn = DBUtil.getConnection();
try {
//2.获取预处理块对象 preparestatement
ps = conn.prepareStatement(sql);
//3.绑定参数
ps.setString(1, name);
ps.setString(2, pwd);
//4.执行SQL语句 5.获取结果集
rs = ps.executeQuery();
//6.遍历结果集存放到 user对象中
while(rs.next()){
int id = rs.getInt("id");
String name2 = rs.getString("name");
String pwd2 = rs.getString("pwd");
//将数据放到对象中
user = new T_user(id,name2,pwd2);
}
} catch (SQLException e) {
e.printStackTrace();
}finally{
//7.关闭资源
DBUtil.closeAll(rs, ps, conn);
}
return user;
}
}
servlet层【获取前端页面登录验证】
package boom.servlet.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 boom.servlet.dao.UserDaoImpl;
import boom.servlet.entity.T_user;
/**
* 获取前端页面登录验证
* @author Administrator
*
*/
public class UserLogin extends HttpServlet {
@Override
protected void service(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
// 1、获取login用户提交的数据【账户，密码】
String uname = request.getParameter("uname");
String pwd = request.getParameter("pwd");
// 2、调用业务逻辑层。简化后调用dao层
UserDaoImpl daoImpl = new UserDaoImpl();
T_user user = daoImpl.getUser(uname, pwd);
String path = "/login.html";
if (user != null) {
path = "/success.html";
} else {
path = "/error.html";
}
// 3 根据dao的查询结果 ，跳转到成功或失败页面
request.getRequestDispatcher(path).forward(request, response); }
}
test层【测试dao层是否连接成功】
package boom.servlet.test; import boom.servlet.dao.UserDaoImpl;
import boom.servlet.entity.T_user; /**
* 测试dao层
* @author Administrator
*
*/
public class TestUserDao {
public static void main(String[] args) {
UserDaoImpl daoImpl = new UserDaoImpl();
T_user user = daoImpl.getUser("boom", "123");
if(user != null){
System.out.println("登录成功");
}else{
System.out.println("登录失败");
}
}
}
数据库配置文件【db.properties】
演示界面：
