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這篇文章主要介紹“怎么用JavaWeb實現登錄功能”的相關知識，小編通過實際案例向大家展示操作過程，操作方法簡單快捷，實用性強，希望這篇“怎么用JavaWeb實現登錄功能”文章能幫助大家解決問題。
本項目實現了登錄功能。點擊首頁的“我要登錄”鏈接跳轉到登錄頁面。在登錄頁面，輸入用戶名和密碼，點擊登錄，提交給LoginServlet處理。查詢數據庫表中的數據。如果用戶名和密碼正確，會跳轉到登錄成功頁面;如果用戶名或密碼錯誤，請求將被轉發到登錄頁面。
開發工具：spring-tool-suite-4
數據庫：Mysql
服務器：tomcat7
jdk：1.8
/*
Navicat MySQL Data Transfer
Source Server : localhost
Source Server Version : 50716
Source Host : localhost:3306
Source Database : test
Target Server Type : MYSQL
Target Server Version : 50716
File Encoding : 65001
Date: 2020-07-30 10:28:07
*/SET FOREIGN_KEY_CHECKS=0;-- ------------------------------ Table structure for users-- ----------------------------DROP TABLE IF EXISTS `users`;CREATE TABLE `users` ( `id` int(11) NOT NULL AUTO_INCREMENT, `username` varchar(100) NOT NULL, `password` varchar(100) NOT NULL, `email` varchar(100) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;-- ------------------------------ Records of users-- ----------------------------INSERT INTO `users` VALUES ('1', 'admin', '123456', 'admin@atguigu.com');4.項目實施
(1)在bean包中，我們實現了User實體類，定義了User對象的私有成員變量，封裝了get和set方法，構造了帶參數和不帶參數的方法，重寫了toString方法
package com.atguigu.bean;public class User {
private int id; private String username; private String password; private String email;
public User() { super();
} public User(int id, String username, String password, String email) { super(); this.id = id; this.username = username; this.password = password; this.email = 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) { this.email = email;
} @Override
public String toString() { return "User [id=" + id + ", username=" + username + ", password=" + password + ", email=" + email + "]";
}
}(2)在dao包中定義了User dao接口，使用User daoimpl類繼承該接口，重寫了接口中的checkUsernameAndPassword方法。該方法可以根據用戶名和密碼查詢數據庫中的相應記錄。如果是，則返回一個 User 對象;否則返回 null
用戶道接口代碼如下
package com.atguigu.dao;import com.atguigu.bean.User;public interface UserDao { /**
* Query the corresponding records in the database according to the user name and password
* @param username
* @param Password
* @return User This record is null, but there is no such record
*/
User checkUsernameAndPassword(String username,String Password);
}UserDaoImpl 代碼如下
package com.atguigu.dao.impl;import com.atguigu.bean.User;import com.atguigu.dao.BasicDao;import com.atguigu.dao.UserDao;public class UserDaoImpl implements UserDao { //establish BasicDao object
BasicDao basicDao = new BasicDao();
@Override
public User checkUsernameAndPassword(String username, String password) { //write sql sentence
String sql = "select id,username,password,email from users where username = ? and password = ?";
User user = basicDao.getBean(User.class, sql, username,password); return user;
}
}BasicDao 類提供了用于添加、刪除、修改和查詢數據庫的 Dao。代碼如下
package com.atguigu.dao;import java.sql.Connection;import java.sql.SQLException;import org.apache.commons.dbutils.QueryRunner;import org.apache.commons.dbutils.handlers.BeanHandler;import com.atguigu.utils.JDBCUtils;public class BasicDao { /*
* Dao is provided to add, delete and modify the database
*/
private QueryRunner queryRunner = new QueryRunner();
/**
* General method of adding, deleting and modifying
* @param sql
* @param params
* @return
*/
public int update(String sql,Object... params) { //Get connection
Connection connection = JDBCUtils.getConnection(); int count = 0; try {
count = queryRunner.update(connection, sql, params);
}catch(SQLException e) {
e.printStackTrace();
}finally {
JDBCUtils.releaseConnection(connection);
} return count;
}
/**
* Method to get an object
* @param <T>
* @param type
* @param sql
* @param params
* @return
*/
public <T> T getBean(Class<T> type,String sql,Object... params) { //Get connection
Connection connection = JDBCUtils.getConnection();
T t = null; try {
t = queryRunner.query(connection, sql, new BeanHandler<T>(type), params);
}catch(SQLException e) {
e.printStackTrace();
}finally {
JDBCUtils.releaseConnection(connection);
} return t;
}
}(3)在servlet包下定義了一個servlet，LoginServlet。doGet 和 doPost 方法用于處理用戶登錄請求
package com.atguigu.servlet;import java.io.IOException;import javax.servlet.RequestDispatcher;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.atguigu.bean.User;import com.atguigu.dao.UserDao;import com.atguigu.dao.impl.UserDaoImpl;/**
* Servlet s that handle user login
*/public class LoginServlet extends HttpServlet { private static final long serialVersionUID = 1L;
public LoginServlet() { super();
} protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //Get user name and password
String username = request.getParameter("username");
String password = request.getParameter("password"); //establish UserDao object
UserDao userDao = new UserDaoImpl(); //call UserDao The password and user name verification method
User user = userDao.checkUsernameAndPassword(username, password); if(user != null) { //The user name and password are correct
response.sendRedirect(request.getContextPath()+"/pages/login_success.html");
}else { //Username or password incorrect
//Get transponder
RequestDispatcher requestDispatcher = request.getRequestDispatcher("/pages/login.html"); //Forward request
requestDispatcher.forward(request, response);
}
} protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}(4) 測試包，負責單元測試
ConnectionTest 類測試數據庫是否連接成功
package com.atguigu.test;import java.sql.Connection;import org.junit.jupiter.api.Test;import com.atguigu.utils.JDBCUtils;class ConnectionTest { @Test
void test() {
Connection connection = JDBCUtils.getConnection();
System.out.println(connection);
}
}UserdaoTest類測試UserDao接口的方法是否可以實現
package com.atguigu.test;import org.junit.jupiter.api.Test;import com.atguigu.bean.User;import com.atguigu.dao.UserDao;import com.atguigu.dao.impl.UserDaoImpl;class UserDaoTest {
UserDao userDao = new UserDaoImpl();
@Test
void testCheckUsernameAndPassword() {
User user = userDao.checkUsernameAndPassword("admin", "123456");
System.out.println(user);
}
}(5)utils包下定義了JDBC utils工具類，用于獲取和釋放Connection連接
package com.atguigu.utils;import java.sql.Connection;import java.sql.SQLException;import java.util.Properties;import javax.sql.DataSource;import com.alibaba.druid.pool.DruidDataSourceFactory;/*
* Tool class for getting and releasing connections
*/public class JDBCUtils { private static DataSource dataSource;
static { try { //1,read druid.properties file
Properties pro = new Properties();
pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"));
//2,Connection pool
dataSource = DruidDataSourceFactory.createDataSource(pro);
}catch(Exception e) {
e.printStackTrace();
}
}
//Get connection
public static Connection getConnection() {
Connection connection = null; try {
connection = dataSource.getConnection();
}catch(SQLException e) {
e.printStackTrace();
} return connection;
}
//Release the connection
public static void releaseConnection(Connection connection) { if(connection != null) { try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}(6)在config源文件中，定義druid配置文件，配置數據庫連接池的相關屬性
# key=valuedriverClassName=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/test?rewriteBatchedStatements=true username=root password=root initialSize=10 minIdle=5 maxActive=20 maxWait=5000
(7)jar包說明：對應的jar包可以從maven中央倉庫下載，復制到WEB-INF下的lib文件夾下
(8)首頁說明
索引，html頁面代碼
<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title><!-- base In the label href Property makes the relative path in the current page an absolute path --><base href="http://localhost:8080/Web_Ex/"></head><body> <!-- with / The first path is the absolute path In absolute path / What does it stand for If the path is resolved by the browser, then / On behalf of http://localhost:8080/ Which paths are resolved by the browser? 1)HTML The path in the label, such as a In the label href The path in the property, form In the label action Path in attribute, etc 2)Paths in redirection If the path is resolved by the server, then / On behalf of http://localhost:8080/Web_Ex/ Which paths are resolved by the server? 1)web.xml In the configuration file url-pattern Path in label 2)Path in forwarding --> <a href="pages/login.html">I want to log in</a><br><br> <a href="#">I want to register</a></body></html>
login.html 頁面代碼
<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title><style type="text/css">
body{ background-color: pink;
}</style><!-- base In the label href Property makes the relative path in the current page an absolute path --><base href="http://localhost:8080/Web_Ex/"></head><body>
<h1>Welcome to login</h1>
<form action="LoginServlet" method="post">
User name:<input type="text" name="username" /><br>
User password:<input type="password" name="password" /><br>
<input type="submit" value="Sign in">
</form></body></html>login_success.html 代碼
<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title><!-- base In the label href Property makes the relative path in the current page an absolute path --><base href="http://localhost:8080/Web_Ex/"></head><body> <h1>Login successful</h1> <a href="index.html">Home </a></body></html>
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