java连接mysql实现图书表和读者表的建立，完成增删改查，要求图书表有外键约束和用户连接起来

好的，我可以给您提供一个大致的实现思路：

1. 首先需要在 MySQL 中创建两个表，分别是图书表和读者表。其中，图书表需要设置外键约束，连接读者表的主键。示例 SQL 语句如下：

CREATE TABLE book (
    id INT(11) PRIMARY KEY,
    title VARCHAR(255),
    author VARCHAR(255),
    reader_id INT(11),
    FOREIGN KEY (reader_id) REFERENCES reader(id)
);

CREATE TABLE reader (
    id INT(11) PRIMARY KEY,
    name VARCHAR(255),
    age INT(11),
    gender VARCHAR(255)
);

2. 在 Java 中，使用 JDBC 连接 MySQL 数据库，并编写相应的增删改查方法。示例代码如下：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class BookManager {
    private Connection conn;
    
    public BookManager() throws SQLException {
        String url = "jdbc:mysql://localhost:3306/db_name";
        String user = "username";
        String password = "password";
        conn = DriverManager.getConnection(url, user, password);
    }
    
    public void addBook(Book book) throws SQLException {
        String sql = "INSERT INTO book (id, title, author, reader_id) VALUES (?, ?, ?, ?)";
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setInt(1, book.getId());
        pstmt.setString(2, book.getTitle());
        pstmt.setString(3, book.getAuthor());
        pstmt.setInt(4, book.getReaderId());
        pstmt.executeUpdate();
        pstmt.close();
    }
    
    public void deleteBook(int id) throws SQLException {
        String sql = "DELETE FROM book WHERE id = ?";
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setInt(1, id);
        pstmt.executeUpdate();
        pstmt.close();
    }
    
    public void updateBook(Book book) throws SQLException {
        String sql = "UPDATE book SET title = ?, author = ?, reader_id = ? WHERE id = ?";
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setString(1, book.getTitle());
        pstmt.setString(2, book.getAuthor());
        pstmt.setInt(3, book.getReaderId());
        pstmt.setInt(4, book.getId());
        pstmt.executeUpdate();
        pstmt.close();
    }
    
    public Book getBook(int id) throws SQLException {
        String sql = "SELECT * FROM book WHERE id = ?";
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setInt(1, id);
        ResultSet rs = pstmt.executeQuery();
        Book book = null;
        if (rs.next()) {
            book = new Book();
            book.setId(rs.getInt("id"));
            book.setTitle(rs.getString("title"));
            book.setAuthor(rs.getString("author"));
            book.setReaderId(rs.getInt("reader_id"));
        }
        rs.close();
        pstmt.close();
        return book;
    }
    
    public Reader getReader(int id) throws SQLException {
        String sql = "SELECT * FROM reader WHERE id = ?";
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setInt(1, id);
        ResultSet rs = pstmt.executeQuery();
        Reader reader = null;
        if (rs.next()) {
            reader = new Reader();
            reader.setId(rs.getInt("id"));
            reader.setName(rs.getString("name"));
            reader.setAge(rs.getInt("age"));
            reader.setGender(rs.getString("gender"));
        }
        rs.close();
        pstmt.close();
        return reader;
    }
}

3. 在代码中，Book 和 Reader 分别是表示图书和读者的实体类。示例代码如下：

public class Book {
    private int id;
    private String title;
    private String author;
    private int readerId;
    
    // 省略 getter 和 setter 方法
}

public class Reader {
    private int id;
    private String name;
    private int age;
    private String gender;
    
    // 省略 getter 和 setter 方法
}

4. 最后，在应用中调用 BookManager 类的方法即可完成增删改查操作。例如，添加一本图书的代码如下：

Book book = new Book();
book.setId(1);
book.setTitle("Java 编程思想");
book.setAuthor("Bruce Eckel");
book.setReaderId(1);

BookManager bookManager = new BookManager();
bookManager.addBook(book);

这样就完成了 Java 连接 MySQL 实现图书表和读者表的建立，实现了增删改查，并且图书表设置了外键约束，连接了读者表。