使用Servlet和JDBC编程来实现一个简单的博客系统（1）

package model; import com.mysql.jdbc.jdbc2.optional.MysqlDataSource; import javax.sql.DataSource; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; // 管理数据库连接 // 1) 建立连接 // 2) 断开连接 // JDBC 中使用 DataSource 来管理连接. // DBUtil 相当于是对 DataSource 再稍微包装一层. // DataSource 每个应用程序只应该有一个实例~~ (单例) // DBUtil 本质上就是实现了一个单例模式, 管理了唯一的一个 DataSource 实例 // 单例模式的实现, 有两种风格: // 1. 饿汉模式 // 2. 懒汉模式. // 此处使用懒汉模式 public class DBUtil { private static volatile DataSource dataSource = null; private static final String URL = "jdbc:mysql://127.0.0.1:3306/java1109_blogdemo?characterEncoding=utf-8&useSSL=true"; private static final String USERNAME = "root"; private static final String PASSWORD = "123456"; public static DataSource getDataSource() { if (dataSource == null) { synchronized (DBUtil.class) { if (dataSource == null) { dataSource = new MysqlDataSource(); // 还需要给 DataSource 设置一些属性. ((MysqlDataSource)dataSource).setURL(URL); ((MysqlDataSource)dataSource).setUser(USERNAME); ((MysqlDataSource)dataSource).setPassword(PASSWORD); } } } return dataSource; } // 通过这个方法来获取连接 public static Connection getConnection() { try { return getDataSource().getConnection(); } catch (SQLException e) { e.printStackTrace(); } return null; } // 通过这个方法来断开连接 public static void close(Connection connection, PreparedStatement statement, ResultSet resultSet) { try { if (resultSet != null) { resultSet.close(); } if (statement != null) { statement.close(); } if (connection != null) { connection.close(); } } catch (SQLException e) { e.printStackTrace(); } } }

package model; public class User { private int userId; private String name; private String password; public int getUserId() { return userId; } public void setUserId(int userId) { this.userId = userId; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Override public String toString() { return "User{" + "userId=" + userId + ", name='" + name + '\'' + ", password='" + password + '\'' + '}'; } }

package model; public class Article { private int articleId; private String title; private String content; private int userId; public int getArticleId() { return articleId; } public void setArticleId(int articleId) { this.articleId = articleId; } public String getTitle() { return title; } public void setTitle(String title) { this.title = title; } public String getContent() { return content; } public void setContent(String content) { this.content = content; } public int getUserId() { return userId; } public void setUserId(int userId) { this.userId = userId; } @Override public String toString() { return "Article{" + "articleId=" + articleId + ", title='" + title + '\'' + ", content='" + content + '\'' + ", userId=" + userId + '}'; } }

package model; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; public class UserDao { // 1. 新增用户(注册) // 把一个 User 对象插入到数据库中. public void add(User user) { // (1). 获取到数据库连接. Connection connection = DBUtil.getConnection(); // (2). 拼装 SQL 语句 String sql = "insert into user values (null, ?, ?)"; PreparedStatement statement = null; try { statement = connection.prepareStatement(sql); statement.setString(1, user.getName()); statement.setString(2, user.getPassword()); // (3). 执行 SQL 语句 int ret = statement.executeUpdate(); if (ret != 1) { System.out.println("插入新用户失败!"); return; } System.out.println("插入新用户成功"); } catch (SQLException e) { e.printStackTrace(); } finally { // (4). 释放数据库的连接. DBUtil.close(connection, statement, null); } } // 2. 按照名字查找用户(登陆) public User selectByName(String name) { // (1). 和数据库建立连接. Connection connection = DBUtil.getConnection(); // (2). 拼装 SQL String sql = "select * from user where name = ?"; PreparedStatement statement = null; ResultSet resultSet = null; try { statement = connection.prepareStatement(sql); statement.setString(1, name); // (3). 执行 SQL resultSet = statement.executeQuery(); // (4). 遍历结果集. 预期 name 在数据库中不能重复. // 此处查找最多只能查出一条记录来. if (resultSet.next()) { User user = new User(); user.setUserId(resultSet.getInt("userId")); user.setName(resultSet.getString("name")); user.setPassword(resultSet.getString("password")); return user; } } catch (SQLException e) { e.printStackTrace(); } finally { DBUtil.close(connection, statement, resultSet); } return null; } // 3.根据用户 id 找到用户信息 public User selectById(int userId) { // (1). 和数据库建立连接. Connection connection = DBUtil.getConnection(); // (2). 拼装 SQL String sql = "select * from user where userId = ?"; PreparedStatement statement = null; ResultSet resultSet = null; try { statement = connection.prepareStatement(sql); statement.setInt(1, userId); // (3). 执行 SQL resultSet = statement.executeQuery(); // (4). 遍历结果集. 预期 name 在数据库中不能重复. // 此处查找最多只能查出一条记录来. if (resultSet.next()) { User user = new User(); user.setUserId(resultSet.getInt("userId")); user.setName(resultSet.getString("name")); user.setPassword(resultSet.getString("password")); return user; } } catch (SQLException e) { e.printStackTrace(); } finally { DBUtil .close(connection, statement, resultSet); } return null; } public static void main(String[] args) { UserDao userDao = new UserDao(); // 1. 先测试 add 方法 /*User user = new User(); user.setName("tmr"); user.setPassword("123"); userDao.add(user); // 2. 测试 selectByName User user = userDao.selectByName("tmr"); System.out.println(user);*/ } }

package model; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; public class ArticleDao { // 1. 新增文章(发布博客) public void add(Article article) { // 1. 获取数据库连接 Connection connection = DBUtil.getConnection(); // 2. 构造 SQL String sql = "insert into article values (null, ?, ?, ?)"; PreparedStatement statement = null; try { statement = connection.prepareStatement(sql); statement.setString(1, article.getTitle()); statement.setString(2, article.getContent()); statement.setInt(3, article.getUserId()); // 3. 执行 SQL int ret = statement.executeUpdate(); if (ret != 1) { System.out.println("执行插入文章操作失败"); return; } System.out.println("执行插入文章操作成功"); } catch (SQLException e) { e.printStackTrace(); } finally { // 4. 释放连接. DBUtil.close(connection, statement, null); } } // 2. 查看文章列表(把所有的文章信息都查出来(没必要查正文)) public List

selectAll() { List

articles = new ArrayList<>(); // 1. 建立连接 Connection connection = DBUtil.getConnection(); // 2. 拼装 SQL String sql = "select articleId, title, userId from article"; PreparedStatement statement = null; ResultSet resultSet = null; try { if (connection != null) { statement = connection.prepareStatement(sql); } // 3. 执行 SQL resultSet = statement.executeQuery(); // 4. 遍历结果集 while (resultSet.next()) { // 针对每个结果记录, 都构造一个对应的 Article 对象. // 此时由于没有从数据库中读 content 字段, 这个字段暂时先不设置. Article article = new Article(); article.setArticleId(resultSet.getInt("articleId")); article.setTitle(resultSet.getString("title")); article.setUserId(resultSet.getInt("userId")); articles.add(article); } return articles; } catch (SQLException e) { e.printStackTrace(); } finally { DBUtil.close(connection, statement, resultSet); } return null; } // 3. 查看指定文章详情. (需要查正文) public Article selectById(int articleId) { // 1. 建立数据库连接 Connection connection = DBUtil.getConnection(); // 2. 构造 SQL String sql = "select * from article where articleId = ?"; PreparedStatement statement = null; ResultSet resultSet = null; try { statement = connection.prepareStatement(sql); statement.setInt(1, articleId); // 3. 执行 SQL resultSet = statement.executeQuery(); // 4. 遍历结果集合. // 由于 id 是主键. 不会重复. 预期最多只能查出一条记录. if (resultSet.next()) { Article article = new Article(); article.setArticleId(resultSet.getInt("articleId")); article.setTitle(resultSet.getString("title")); article.setContent(resultSet.getString("content")); article.setUserId(resultSet.getInt("userId")); return article; } } catch (SQLException e) { e.printStackTrace(); } finally { // 5. 释放连接. DBUtil.close(connection, statement, resultSet); } return null; } // 4. 删除指定文章(给定文章 id 来删除) public void delete(int articleId) { // 1. 获取连接 Connection connection = DBUtil.getConnection(); // 2. 拼装 SQL String sql = "delete from article where articleId = ?"; PreparedStatement statement = null; try { statement = connection.prepareStatement(sql); statement.setInt(1, articleId); // 3. 执行 SQL int ret = statement.executeUpdate(); if (ret != 1) { System.out.println("删除文章失败"); return; } System.out.println("删除文章成功"); } catch (SQLException e) { e.printStackTrace(); } finally { // 4. 释放连接. DBUtil.close(connection, statement, null); } } public static void main(String[] args) { ArticleDao articleDao = new ArticleDao(); // 1. 测试新增文章 Article article = new Article(); article.setTitle("woshibiaoti1"); article.setContent("zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1zhengwen1"); article.setUserId(1); articleDao.add(article); // 2. 测试查看文章列表 List

articles = articleDao.selectAll(); System.out.println(articles); // 3. 查看指定文章内容 //Article article = articleDao.selectById(1); //System.out.println(article); // 4. 删除文章 // articleDao.delete(2); } }

使用Servlet和JDBC编程来实现一个简单的博客系统（1）

你可能感兴趣的:(intellij-idea,maven,java)