Java代码示例：用于从数据库中查询图书信息

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

// 图书实体类（对应数据库表结构）
class Book {
    private int id;
    private String title;
    private String author;
    private String isbn;
    private int status;

    // 构造方法
    public Book(int id, String title, String author, String isbn, int status) {
        this.id = id;
        this.title = title;
        this.author = author;
        this.isbn = isbn;
        this.status = status;
    }

    //  toString方法（用于打印图书信息）
    @Override
    public String toString() {
        return "ID: " + id + 
               ", 书名: " + title + 
               ", 作者: " + author + 
               ", ISBN: " + isbn + 
               ", 状态: " + (status == 1 ? "可借阅" : "已借出");
    }
}

// 图书查询工具类
public class BookQueryExample {
    // 数据库连接信息（请替换为你的实际配置）
    private static final String DB_URL = "jdbc:mysql://localhost:3306/library?useSSL=false&serverTimezone=UTC";
    private static final String USER = "root";       // 数据库用户名
    private static final String PASSWORD = "123456"; // 数据库密码

    public static void main(String[] args) {
        // 查询所有图书
        List<Book> allBooks = queryAllBooks();
        System.out.println("=== 所有图书信息 ===");
        for (Book book : allBooks) {
            System.out.println(book);
        }

        // 按条件查询（例如查询可借阅的图书）
        List<Book> availableBooks = queryBooksByStatus(1);
        System.out.println("\n=== 可借阅图书 ===");
        for (Book book : availableBooks) {
            System.out.println(book);
        }
    }

    /**
     * 查询所有图书
     */
    public static List<Book> queryAllBooks() {
        List<Book> books = new ArrayList<>();
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;

        try {
            // 1. 加载数据库驱动（MySQL 8.0+ 无需显式加载，可省略）
            Class.forName("com.mysql.cj.jdbc.Driver");

            // 2. 获取数据库连接
            conn = DriverManager.getConnection(DB_URL, USER, PASSWORD);

            // 3. 编写SQL语句
            String sql = "SELECT id, title, author, isbn, status FROM books";

            // 4. 创建PreparedStatement（预编译SQL，防止SQL注入）
            pstmt = conn.prepareStatement(sql);

            // 5. 执行查询，获取结果集
            rs = pstmt.executeQuery();

            // 6. 处理结果集
            while (rs.next()) {
                int id = rs.getInt("id");
                String title = rs.getString("title");
                String author = rs.getString("author");
                String isbn = rs.getString("isbn");
                int status = rs.getInt("status");

                // 将查询结果封装为Book对象
                books.add(new Book(id, title, author, isbn, status));
            }

        } catch (ClassNotFoundException e) {
            System.out.println("数据库驱动加载失败：" + e.getMessage());
        } catch (SQLException e) {
            System.out.println("数据库操作失败：" + e.getMessage());
        } finally {
            // 7. 关闭资源（顺序：ResultSet -> PreparedStatement -> Connection）
            try {
                if (rs != null) rs.close();
                if (pstmt != null) pstmt.close();
                if (conn != null) conn.close();
            } catch (SQLException e) {
                System.out.println("资源关闭失败：" + e.getMessage());
            }
        }

        return books;
    }

    /**
     * 按状态查询图书（1-可借阅，0-已借出）
     */
    public static List<Book> queryBooksByStatus(int status) {
        List<Book> books = new ArrayList<>();
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;

        try {
            conn = DriverManager.getConnection(DB_URL, USER, PASSWORD);
            String sql = "SELECT id, title, author, isbn, status FROM books WHERE status = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, status); // 设置SQL中的参数（?占位符）
            rs = pstmt.executeQuery();

            while (rs.next()) {
                books.add(new Book(
                        rs.getInt("id"),
                        rs.getString("title"),
                        rs.getString("author"),
                        rs.getString("isbn"),
                        rs.getInt("status")
                ));
            }

        } catch (SQLException e) {
            System.out.println("查询失败：" + e.getMessage());
        } finally {
            // 关闭资源（同上）
            try {
                if (rs != null) rs.close();
                if (pstmt != null) pstmt.close();
                if (conn != null) conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        return books;
    }
}