网站开发用什么软件,seo网站页面f布局,适合前端新手做的网页,c s网站开发模式JDBC#xff08;Java Database Connectivity#xff09;是Java编程语言中用于与数据库建立连接并进行数据库操作的API#xff08;应用程序编程接口#xff09;。JDBC允许开发人员连接到数据库#xff0c;执行各种操作#xff08;如插入、更新、删除和查询数据#xff09…JDBCJava Database Connectivity是Java编程语言中用于与数据库建立连接并进行数据库操作的API应用程序编程接口。JDBC允许开发人员连接到数据库执行各种操作如插入、更新、删除和查询数据并检索结果。
JDBC提供了一个标准的方法使Java应用程序能够与各种类型的数据库进行交互使其在某种程度上与数据库无关。它是Java中用于数据库连接的基本技术使开发人员能够构建与数据库交互的强大应用程序。
下面我们通过具体的实验来学习它主要下面几个部分。 内容 一、JDBC快速入门实验 1.创建数据库db_myweb和account表三个字段id、name、money 2.创建eclipse项目导入MySQL驱动包 3.编写数据库操作7个步骤代码实现数据更新 4.查看结果 二、利用Junit实现JDBC的增晒改查实验 1.给项目添加JUnit单元测试创建JDBCTest测试用例类 2.添加5个测试方法分别为 public void testInsert(){} public void testUpdate(){} public void testDelete(){} public void testFindAll(){} public void testFind(){} 3.对5个方法测试并查看测试结果 三、完成SQL注入实验并对比结果 四、完成转账事务控制实验并对比结果 五、自定义封装JDBC连接工具类 1.第一代JDBCUtils类封装与测试查看结果 2.第二代JDBCUtils类封装与测试查看结果 六、封装增删改查DAO 1.创建tb_user表字段有id username password email birthday 2.创建JavaBeanUser.java 3.创建工具类JDBCUtils.java 4.创建数据库访问层DAO类封装增删改查代码UserDao.java 5.利用JUnit对DAO的方法进行单元测试并查看结果 七、完成网站登录程序实验 1.创建登录页面login.jsp 2.UserDao增加方法按用户名和密码查询方法 3.创建登录功能的LoginServlet.java 4.运行项目查看效果
OK话不多说直接开始
1.创建数据库db_myweb和account表三个字段id、name、money 创建db_myweb数据库 create database db_myweb charsetutf8;使用db_myweb数据库
use db_myweb;创建表account表三个字段id、name、money:
CREATE TABLE account (id int NOT NULL AUTO_INCREMENT,name varchar(25) DEFAULT NULL,money double DEFAULT NULL,PRIMARY KEY (id)
);2.创建eclipse项目导入MySQL驱动包 创建JDBC web动态工程lib目录下导入mysql-connector-java-5.1.48.jar 驱动包。 Build Path把sql驱动包加到路径里面。 3.编写数据库操作7个步骤代码实现数据更新
package com.java5678.Demo;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;public class JDBCDemo {public static void main(String[] args) throws Exception {//1. 注册驱动Class.forName(com.mysql.jdbc.Driver);/*2. 获取连接*/String url jdbc:mysql://localhost:3306/db_myweb;String username root;String password root;Connection conn DriverManager.getConnection(url, username, password);//3. 定义sql/*String sql insert into account value(2,li,2);*/String sql update account set money 2000 where id 1;/*4. 获取执行sql的对象 Statement*/Statement stmt conn.createStatement();/*5. 执行sql*/int count stmt.executeUpdate(sql);//受影响的行数/*6. 处理结果*/System.out.println(count);/*7. 释放资源*/stmt.close();conn.close();}
}数据库账号密码都是root 4.查看结果 db_myweb数据库里面的account表里面id为一的信息成功从300更新2000 利用Junit实现JDBC的增删改查实验 1.给项目添加JUnit单元测试创建JDBCTest测试用例类 创建工具类JDBCUtils
package chapter02.jdbc.example;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class JDBCUtils {
public static Connection getConnection() throws SQLException,ClassNotFoundException{
Class.forName(com.mysql.jdbc.Driver);
String url jdbc:mysql://localhost:3306/db_myweb?serverTimezoneUTC;
String username root;
String password root;
Connection conn DriverManager.getConnection(url,username,password);
return conn;
}
public static void release(Statement stmt, Connection conn) {
if(stmt!null) {
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
stmt null;
}
if(conn!null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
connnull;
}
}
public static void release(ResultSet rs,Statement stmt,Connection conn) {
if(rs!null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
rs null;
}
release(stmt, conn);
}
}2.添加5个测试方法
package chapter02.jdbc.example;import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.text.SimpleDateFormat;
import java.util.ArrayList;import com.javaweb.bean.user;public class UsersDao {
//添加用户的操作
public boolean insert(user user) {
Connection conn null;
Statement stmtnull;
ResultSet rs null;
try {
conn JDBCUtils.getConnection();
stmt conn.createStatement();
SimpleDateFormat sdf new SimpleDateFormat(yyyy-MM-dd);
String birthday sdf.format(user.getBirthday());
String sql INSERT INTO tb_user(id,username,password,email,birthday)
VALUES(
user.getId()
,
user.getUsername()
,
user.getPassword()
,
user.getEmail()
,
birthday );
System.out.println(sql);
int num stmt.executeUpdate(sql);
if (num 0) {
return true;
}
return false;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.release(rs,stmt,conn);
}
return false;
}
public ArrayListuser findAll(){
Connection conn null;
Statement stmtnull;
ResultSet rs null;
ArrayListuser list new ArrayListuser();
try {
conn JDBCUtils.getConnection();
stmt conn.createStatement();
String sql SELECT * FROM tb_user;
rs stmt.executeQuery(sql);
while(rs.next()) {
user user new user();
user.setId(rs.getInt(id));
user.setUsername(rs.getString(username));
user.setPassword(rs.getString(password));
user.setEmail(rs.getString(email));
user.setBirthday(rs.getDate(birthday));
list.add(user);
}
return list;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.release(rs, stmt, conn);
}
return null;
}
public user find(int id) {
Connection connnull;
Statement stmtnull;
ResultSet rs null;
try {
conn JDBCUtils.getConnection();
stmtconn.createStatement();
String sql SELECT * FROM tb_user WHERE id id;
rs stmt.executeQuery(sql);
while(rs.next()) {
user user new user();
user.setId(rs.getInt(id));
user.setUsername(rs.getString(username));
user.setPassword(rs.getString(password));
user.setEmail(rs.getString(email));
user.setBirthday(rs.getDate(birthday));
return user;
}
return null;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.release(rs,stmt, conn);
}
return null;
}
public boolean delete(int id) {
Connection conn null;
Statement stmt null;
ResultSet rs null;
try {
conn JDBCUtils.getConnection();
stmt conn.createStatement();
String sql DELETE FROM tb_user WHERE id id;
int num stmt.executeUpdate(sql);
if(num 0) {
return true;
}
return false;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.release(rs, stmt,conn);
}
return false;
}
public boolean update(user user) {
Connection conn null;
Statement stmt null;
ResultSet rs null;
try {
conn JDBCUtils.getConnection();
stmt conn.createStatement();
SimpleDateFormat sdf new SimpleDateFormat(yyyy-MM-dd);
String birthday sdf.format(user.getBirthday());
String sql UPDATE tb_user set usernameuser.getUsername()
,passworduser.getPassword() ,email
user.getEmail() ,birthday birthday
WHERE id user.getId();
int num stmt.executeUpdate(sql);
if (num 0) {
return true;
}
return false;
} catch (Exception e) {
e.printStackTrace();
}finally {
JDBCUtils.release(rs, stmt, conn);
}
return false;
}
}3.对5个方法测试并查看测试结果 添加测试类JDBCTest实现向tb_usr插入数据库
package chapter02.jdbc.example;
import java.util.ArrayList;
import java.util.Date;import com.javaweb.bean.user;Test
public class JDBCTest {public static void main(String[] args) {//向users表插入一个用户信息UsersDao ud new UsersDao();user usernew user();user.setId(8);user.setUsername(hfdsdl);user.setPassword(12363);user.setEmail(hl6sina.com);user.setBirthday(new Date());boolean b ud.insert(user);System.out.println(b);}}成功插入数据 编写测试类FindAllUsersTest,该类用于实现读取tb_user表中所有的数据:
package chapter02.jdbc.example;
import java.util.ArrayList;
import com.javaweb.bean.user;public class FindAllUsersTest {public static void main(String[] args) {UsersDao usersDao new UsersDao();ArrayListuser list usersDao.findAll();for (int i0; i list.size(); i) {System.out.println(第 (i1) 条数据的username的值为list.get(i).getUsername());}} 最后成功读取tb_user表中所有的数据 编写测试类UpdateUserTest,在该类中实现修改tb_user表中数据的操作:
package chapter02.jdbc.example;
import java.util.Date;
import com.javaweb.bean.user;public class UpdateUserTest {public static void main(String[] args) {UsersDao usersDao new UsersDao();user user new user();user.setId(5);user.setUsername(zhaoxiaoliu);user.setPassword(456);user.setEmail(zhaoxiaoliusina.com);user.setBirthday(new Date());boolean busersDao.update(user);System.out.println(b);}
}运行结果和查询结果如图所示 编写测试类DeleteUserTest,该类实现了删除tb_user 表中数据的操作:
package chapter02.jdbc.example;
public class DeleteUserTest {public static void main(String[] args) {UsersDao usersDao new UsersDao();boolean b usersDao.delete(5);System.out.println(b);}
}运行结果和sql查询结果如图所示 从图中可以看出users表中id为5的User对象已被成功删除了。至此使用JDBC对数据库中数据进行增删改查的操作已经完成。 完成SQL注入实验并对比结果 SQL注入模拟正常登陆SQL查询 新建testLogin单元测试
package com.java5678.Demo;import static org.junit.Assert.*;import java.sql.DriverManager;
import java.sql.ResultSet;import org.junit.Test;import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;public class testLogin {Testpublic void testLogin() throws Exception {String url jdbc:mysql://localhost:3306/db_myweb;String username root;String password root;Connection conn (Connection) DriverManager.getConnection(url, username, password);// 接收用户输入 用户名和密码String name zl;String pwd 123456;String sql select * from tb_user where username name and password pwd;// 获取stmt对象Statement stmt (Statement) conn.createStatement();// 执行sqlResultSet rs stmt.executeQuery(sql);// 判断登录是否成功if(rs.next()){System.out.println(登录成功~);}else{System.out.println(登录失败~);}//7. 释放资源rs.close();stmt.close();conn.close();}}测试成功 QL注入模拟SQL注入SQL查询 新建单元测试testLogin2单元测试
package com.java5678.Demo;import static org.junit.Assert.*;import java.sql.DriverManager;
import java.sql.ResultSet;import org.junit.Test;import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;public class testLogin2 {Test
public void testLogin_Inject() throws Exception {
//2. 获取连接如果连接的是本机mysql并且端口是默认的 3306 可以简化书写
String url jdbc:mysql://localhost:3306/db_myweb;
String username root;
String password root;
Connection conn (Connection) DriverManager.getConnection(url, username, password);
// 接收用户输入 用户名和密码
String name hfkjsfhskj;
String pwd or 1 1;
String sql select * from tb_user where username name and password pwd;
System.out.println(sql);
// 获取stmt对象
Statement stmt (Statement) conn.createStatement();
// 执行sql
ResultSet rs stmt.executeQuery(sql);// 判断登录是否成功
if(rs.next()){
System.out.println(登录成功~);
}else{
System.out.println(登录失败~);
}//7. 释放资源
rs.close();
stmt.close();
conn.close();
}
}运行testLogin2单元测试发现sql注入成功 完成转账事务控制实验并对比结果 创建JDBCDemo3_Connection java类 开启事务setAutoCommit(boolean autoCommit)true为自动提交事务false为手动提交事务即为开启事务 提交事务commit() 回滚事务rollback()
package com.java5678.Demo;import java.sql.DriverManager;import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;public class JDBCDemo3_Connection {
public static void main(String[] args) throws Exception {
//1. 注册驱动
//Class.forName(com.mysql.jdbc.Driver);
//2. 获取连接如果连接的是本机mysql并且端口是默认的 3306 可以简化书写
String url jdbc:mysql:///db_myweb?useSSLfalse;
String username root;
String password root;
Connection conn (Connection) DriverManager.getConnection(url, username, password);
//3. 定义sql
String sql1 update account set money 3000 where id 1;
String sql2 update account set money 3000 where id 2;
//4. 获取执行sql的对象 Statement
Statement stmt (Statement) conn.createStatement();
try {
// 开启事务
conn.setAutoCommit(false);
//5. 执行sql
int count1 stmt.executeUpdate(sql1);//受影响的行数
//6. 处理结果
System.out.println(count1);
//5. 执行sql
int count2 stmt.executeUpdate(sql2);//受影响的行数
//6. 处理结果
System.out.println(count2);// 提交事务
conn.commit();
} catch (Exception throwables) {
// 回滚事务
conn.rollback();
throwables.printStackTrace();
}
//7. 释放资源
stmt.close();
conn.close();
}
}运行结果 成功完成转账事务 自定义封装JDBC连接工具类 1.第一代JDBCUtils类封装与测试查看结果 在包com.javaweb.utils下面创建testJdbcUtils1类
package com.javaweb.utils;
import java.sql.*;
public class testJdbcUtils1 {public static void main(String[] args) throws Exception {Connection conn JDBCUtils.getconnection();String sqlupdate account set money ? where id ?;PreparedStatement pstm conn.prepareStatement(sql);pstm.setString(1, 20000);pstm.setString(2, 1);int countpstm.executeUpdate();JDBCUtils.close( null,pstm, conn);System.out.println(count);}
}2.第二代JDBCUtils类封装与测试查看结果 在src下创建数据库连接配置文件jdbc.properties
drivercom.mysql.jdbc.Driver
urljdbc:mysql://127.0.0.1:3306/db_myweb?useSSLfalse
userroot
passwordroot创建JDBCUtils2类
package com.javaweb.utils;
import java.io.FileReader;
import java.sql.*;
import java.util.Properties;public class JDBCUtils2 {private static String driver;private static String url;private static String user;private static String password;
static {try {// 1. 创建Properties集合类。Properties properties new Properties();// 2. 加载文件properties.load(new FileReader(JDBCUtils.class.getClassLoader().getResource(jdbc.properties).getPath()));driver properties.getProperty(driver);url properties.getProperty(url);user properties.getProperty(user);password properties.getProperty(password);// 注册驱动Class.forName(driver);} catch (Exception e) {e.printStackTrace();}}
public static Connection getConnection() throws SQLException { return DriverManager.getConnection(url, user, password);}// 释放资源public static void close(ResultSet rs, PreparedStatement pstm, Connection conn) {try {if (rs ! null) {rs.close();}if (pstm ! null) {pstm.close();}if (conn ! null) {conn.close();}} catch (SQLException e) {e.printStackTrace();}}
}第二代JDBCUtils测试
package com.javaweb.utils;
import java.sql.*;
public class testJdbcUtils2 {
public static void main(String[] args) throws Exception {
Connection conn JDBCUtils2.getConnection();
String sql update account set money ? where id ?;
PreparedStatement pstmt conn.prepareStatement(sql);
pstmt.setDouble(1, 5000);
pstmt.setInt(2, 1);
int count pstmt.executeUpdate();
System.out.println(count);
}
}测试结果成功 封装增删改查DAO 1.创建tb_user表字段有id username password email birthday 在MySQL中使用一个名称为db_myweb的数据库然后在该数据库中创建一个tb_user表再向表中插入3条数据。
Use db_mywebCREATE TABLE tb_user(id INT PRIMARY KEY AUTO_INCREMENT,username VARCHAR(40),password VARCHAR(40),email VARCHAR(60),birthday DATE
)CHARACTER SET utf8 COLLATE utf8_general_ci;插入数据
INSERT INTO tb_user(username,password ,email,birthday) VALUES(zs,123456,zssina.com,1980-12-04);
INSERT INTO tb_user(username,password ,email,birthday) VALUES(lisi,123456,lisisina.com,1981-12-04);
INSERT INTO tb_user(username,password ,email,birthday) VALUES(wangwu,123456,wangwusina.com,1979-12-04);2.创建JavaBeanUser.java 在src目录下新建一个名称为chapter02.jdbc.example的包 创建JavaBeanUser类的具体实现方式如下
package com.javaweb.bean;import java.util.Date;public class user {private int id;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) {this.email email;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday birthday;}private String username;private String password;private String email;private Date birthday;}3.创建数据库访问层DAO类封装增删改查代码UserDao.java
package chapter02.jdbc.example;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.text.SimpleDateFormat;
import java.util.ArrayList;import com.javaweb.bean.user;public class UsersDao {//添加用户的操作public boolean insert(user user) {Connection conn null;Statement stmtnull;ResultSet rs null;try {conn JDBCUtils.getConnection();stmt conn.createStatement();SimpleDateFormat sdf new SimpleDateFormat(yyyy-MM-dd);String birthday sdf.format(user.getBirthday());String sql INSERT INTO tb_user(id,username,password,email,birthday)VALUES(user.getId(),user.getUsername(),user.getPassword(),user.getEmail(),birthday );System.out.println(sql);int num stmt.executeUpdate(sql);if (num 0) {return true;}return false;} catch (Exception e) {e.printStackTrace();} finally {JDBCUtils.release(rs,stmt,conn);}return false;}public ArrayListuser findAll(){Connection conn null;Statement stmtnull;ResultSet rs null;ArrayListuser list new ArrayListuser();try {conn JDBCUtils.getConnection();stmt conn.createStatement();String sql SELECT * FROM tb_user;rs stmt.executeQuery(sql);while(rs.next()) {user user new user();user.setId(rs.getInt(id));user.setUsername(rs.getString(username));user.setPassword(rs.getString(password));user.setEmail(rs.getString(email));user.setBirthday(rs.getDate(birthday));list.add(user);}return list;} catch (Exception e) {e.printStackTrace();} finally {JDBCUtils.release(rs, stmt, conn);}return null;}public user find(int id) {Connection connnull;Statement stmtnull;ResultSet rs null;try {conn JDBCUtils.getConnection();stmtconn.createStatement();String sql SELECT * FROM tb_user WHERE id id;rs stmt.executeQuery(sql);while(rs.next()) {user user new user();user.setId(rs.getInt(id));user.setUsername(rs.getString(username));user.setPassword(rs.getString(password));user.setEmail(rs.getString(email));user.setBirthday(rs.getDate(birthday));return user;}return null;} catch (Exception e) {e.printStackTrace();} finally {JDBCUtils.release(rs,stmt, conn);}return null;}public boolean delete(int id) {Connection conn null;Statement stmt null;ResultSet rs null;try {conn JDBCUtils.getConnection();stmt conn.createStatement();String sql DELETE FROM tb_user WHERE id id;int num stmt.executeUpdate(sql);if(num 0) {return true;}return false;} catch (Exception e) {e.printStackTrace();} finally {JDBCUtils.release(rs, stmt,conn);}return false;}public boolean update(user user) {Connection conn null;Statement stmt null;ResultSet rs null;try {conn JDBCUtils.getConnection();stmt conn.createStatement();SimpleDateFormat sdf new SimpleDateFormat(yyyy-MM-dd);String birthday sdf.format(user.getBirthday());String sql UPDATE tb_user set usernameuser.getUsername(),passworduser.getPassword() ,emailuser.getEmail() ,birthday birthdayWHERE id user.getId();int num stmt.executeUpdate(sql);if (num 0) {return true;}return false;} catch (Exception e) {e.printStackTrace();}finally {JDBCUtils.release(rs, stmt, conn);}return false;}
}4.利用JUnit对DAO的方法进行单元测试并查看结果 创建测试类JDBCTESTl利用JUnit对DAO-insert方法添加tb_user表中的数据:
package chapter02.jdbc.example;import java.util.Date;import com.javaweb.bean.user;Test
public class JDBCTest {public static void main(String[] args) {//向users表插入一个用户信息UsersDao ud new UsersDao();user usernew user();user.setId(4);user.setUsername(xiaoli);user.setPassword(00000);user.setEmail(h23526456qq.com);user.setBirthday(new Date());boolean b ud.insert(user);System.out.println(b);}}测试结果 创建测试类JDBCTEST03利用JUnit对DAO-findAll方法根据ID查询tb_user表中数据
package chapter02.jdbc.example;import java.util.ArrayList;import com.javaweb.bean.user;public class FindAllUsersTest {public static void main(String[] args) {UsersDao usersDao new UsersDao();ArrayListuser list usersDao.findAll();for (int i0; i list.size(); i) {System.out.println(第 (i1) 条数据的username的值为list.get(i).getUsername());}}}测试结果成功查询出tb_user表中所有username值 创建测试类JDBCTEST03利用JUnit对DAO-find方法根据ID查询tb_user表中数据 我们根据ID查询tb_user表中ID为13的数据库信息
package chapter02.jdbc.example;import static org.junit.Assert.*;import org.junit.Test;import com.javaweb.bean.user;public class JDBCTEST03 {Testpublic void testFind() throws Exception {UsersDao dao new UsersDao();user userdao.find(13);System.out.println(id为13的User对象的name值为user.getUsername());}}测试结果 成功通过ID查询rb_user表中ID为13的username信息 创建测试类JDBCTEST04利用JUnit对DAO-update方法方法根据ID更新tb_user表中数据
package chapter02.jdbc.example;import java.util.Date;import org.junit.Test;import com.javaweb.bean.user;public class JDBCTEST04 {Testpublic void testUpdate() throws Exception {UsersDao dao new UsersDao();user usernew user();user.setId(13);user.setUsername(项秀才让);user.setPassword(abc);user.setEmail(123456sina.com);user.setBirthday(new Date());boolean bdao.update(user);System.out.println(b);}}测试结果 成功修改ID为13的数据库记录信息 创建测试类JdbcTest01利用DAO-delete方法删除tb_user表中的数据
package chapter02.jdbc.example;
import org.junit.jupiter.api.Test;
class JdbcTest01 {Testpublic void testDelete() {UsersDao dao new UsersDao();boolean bdao.delete(8);System.out.println(b);}
}测试结果和sql查询结果 完成网站登录程序实验 1.创建登录页面login.jsp 在web目录下创建一个名称为login的JSP文件在该文件中添加用于用户登录时输入用户信息的表单元素。
% page languagejava contentTypetext/html; charsetUTF-8pageEncodingUTF-8%
!DOCTYPE html
html
head
meta charsetUTF-8
titleInsert title here/title
/head
body
form action/myweb/LoginServlet methodpost
用户名input typetext nameusername br
密 码input typepassword namepassword br
input typesubmit value登录
/form
/body
/html2.UserDao增加方法按用户名和密码查询方法
// 根据username,password查找指定的user
public boolean findByUsernameAndPassword(String username,String password){
Connection conn null;
PreparedStatement pstmt null;
ResultSet rs null;
try {
// 获得数据的连接
conn JDBCUtils.getConnection();
// 发送SQL语句
String sql select * from tb_user where username? and password?;
// 获得PreparedStatement对象
pstmt (PreparedStatement) conn.prepareStatement(sql);
pstmt.setString(1, username);
pstmt.setString(2, password);
rs pstmt.executeQuery();
// 处理结果集
if (rs.next())
return true;
return false;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.close(rs, pstmt, conn);
}
return false;
}3.创建登录功能的LoginServlet.java
package com.javaweb.servlet;import java.io.IOException;
import java.io.PrintWriter;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;/*** Servlet implementation class LoginServlet*/
WebServlet(/LoginServlet)
public class LoginServlet extends HttpServlet {
/*** */private static final long serialVersionUID 1L;protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding(UTF-8);response.setContentType(text/html;charsetutf-8); PrintWriter out response.getWriter();String usernamerequest.getParameter(username);String passwordrequest.getParameter(password);if(username!nullpassword!null!username.equals()!password.equals()) {UserDao daonew UserDao();boolean bdao.findByUsernameAndPassword(username, password);if(b)out.print(欢迎登录);elseout.print(用户名或密码不正确); }elseout.print(用户名或密码不能为空); }}4.运行项目查看效果 不输入用户名和密码时候登录 输入错误密码时
