javaweb基于JDBC实现单表的CRUD数据库操作

好的，我可以为您解答这个问题。

首先，需要导入JDBC相关的jar包，然后建立数据库连接。以下是一个基本的数据库连接的示例代码：

// 导入JDBC相关的jar包
import java.sql.*;

public class DBUtil {
    // 数据库连接信息
    private static final String URL = "jdbc:mysql://localhost:3306/db_name?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
    private static final String USER = "root";
    private static final String PASSWORD = "123456";

    // 获取数据库连接
    public static Connection getConnection() {
        Connection conn = null;

        try {
            // 注册JDBC驱动
            Class.forName("com.mysql.cj.jdbc.Driver");

            // 建立数据库连接
            conn = DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return conn;
    }
}

接下来，我们可以使用JDBC实现单表的CRUD操作。以下是一个基本的示例代码：

// 导入JDBC相关的jar包
import java.sql.*;

public class UserDaoImpl implements UserDao {
    private Connection conn = null;
    private PreparedStatement pstmt = null;
    private ResultSet rs = null;

    // 构造函数中获取数据库连接
    public UserDaoImpl() {
        conn = DBUtil.getConnection();
    }

    // 关闭数据库连接
    public void close() {
        try {
            if (rs != null) {
                rs.close();
            }

            if (pstmt != null) {
                pstmt.close();
            }

            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 增加数据
    public void add(User user) {
        try {
            String sql = "INSERT INTO user (username, password) VALUES (?, ?)";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUsername());
            pstmt.setString(2, user.getPassword());
            pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 删除数据
    public void delete(int id) {
        try {
            String sql = "DELETE FROM user WHERE id = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 修改数据
    public void update(User user) {
        try {
            String sql = "UPDATE user SET username = ?, password = ? WHERE id = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUsername());
            pstmt.setString(2, user.getPassword());
            pstmt.setInt(3, user.getId());
            pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 查询数据
    public User query(int id) {
        User user = null;

        try {
            String sql = "SELECT * FROM user WHERE id = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            rs = pstmt.executeQuery();

            if (rs.next()) {
                user = new User();
                user.setId(rs.getInt("id"));
                user.setUsername(rs.getString("username"));
                user.setPassword(rs.getString("password"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }

        return user;
    }
}

以上是一个基于JDBC实现单表的CRUD操作的示例代码，您可以根据自己的实际需求进行修改和完善。