JavaBean+Servlet+JSP+DAO（2）设计实现一个图书管理系统。图书信息存放到一个数据库中，图书包含信息：图书号、图书名、作者、价格。请实现对图书的增删改查操作。

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首先，我们需要创建一个数据库来存储图书信息。可以使用MySQL或其他关系型数据库来实现。在数据库中，我们需要创建一个表来存储图书信息，表的字段包括图书号、图书名、作者、价格。

接下来，我们可以使用JavaBean来表示图书信息。我们可以创建一个Book类，它包含图书号、图书名、作者和价格这四个属性，并为每个属性提供getter和setter方法。例如：

public class Book {
    private String bookId;
    private String bookName;
    private String author;
    private double price;

    public String getBookId() {
        return bookId;
    }

    public void setBookId(String bookId) {
        this.bookId = bookId;
    }

    public String getBookName() {
        return bookName;
    }

    public void setBookName(String bookName) {
        this.bookName = bookName;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

接下来，我们可以使用DAO模式来实现对图书信息的增删改查操作。我们可以创建一个BookDAO接口，定义以下方法：

public interface BookDAO {
    public List<Book> getAllBooks() throws SQLException;
    public Book getBookById(String bookId) throws SQLException;
    public void addBook(Book book) throws SQLException;
    public void updateBook(Book book) throws SQLException;
    public void deleteBook(String bookId) throws SQLException;
}

然后，我们可以创建一个BookDAOImpl类来实现BookDAO接口中的方法。例如：

public class BookDAOImpl implements BookDAO {
    private Connection conn;

    public BookDAOImpl(Connection conn) {
        this.conn = conn;
    }

    public List<Book> getAllBooks() throws SQLException {
        List<Book> books = new ArrayList<Book>();
        String sql = "select * from books";
        PreparedStatement ps = conn.prepareStatement(sql);
        ResultSet rs = ps.executeQuery();
        while (rs.next()) {
            Book book = new Book();
            book.setBookId(rs.getString("book_id"));
            book.setBookName(rs.getString("book_name"));
            book.setAuthor(rs.getString("author"));
            book.setPrice(rs.getDouble("price"));
            books.add(book);
        }
        return books;
    }

    public Book getBookById(String bookId) throws SQLException {
        String sql = "select * from books where book_id=?";
        PreparedStatement ps = conn.prepareStatement(sql);
        ps.setString(1, bookId);
        ResultSet rs = ps.executeQuery();
        if (rs.next()) {
            Book book = new Book();
            book.setBookId(rs.getString("book_id"));
            book.setBookName(rs.getString("book_name"));
            book.setAuthor(rs.getString("author"));
            book.setPrice(rs.getDouble("price"));
            return book;
        } else {
            return null;
        }
    }

    public void addBook(Book book) throws SQLException {
        String sql = "insert into books(book_id, book_name, author, price) values (?, ?, ?, ?)";
        PreparedStatement ps = conn.prepareStatement(sql);
        ps.setString(1, book.getBookId());
        ps.setString(2, book.getBookName());
        ps.setString(3, book.getAuthor());
        ps.setDouble(4, book.getPrice());
        ps.executeUpdate();
    }

    public void updateBook(Book book) throws SQLException {
        String sql = "update books set book_name=?, author=?, price=? where book_id=?";
        PreparedStatement ps = conn.prepareStatement(sql);
        ps.setString(1, book.getBookName());
        ps.setString(2, book.getAuthor());
        ps.setDouble(3, book.getPrice());
        ps.setString(4, book.getBookId());
        ps.executeUpdate();
    }

    public void deleteBook(String bookId) throws SQLException {
        String sql = "delete from books where book_id=?";
        PreparedStatement ps = conn.prepareStatement(sql);
        ps.setString(1, bookId);
        ps.executeUpdate();
    }
}

最后，我们可以使用Servlet和JSP来实现用户界面。例如，我们可以创建一个BookServlet类，它处理所有的HTTP请求，并调用DAO中的方法来处理业务逻辑。例如：

public class BookServlet extends HttpServlet {
    private BookDAO bookDAO;

    public void init() throws ServletException {
        Connection conn = getConnection(); // 获取数据库连接
        bookDAO = new BookDAOImpl(conn); // 创建DAO对象
    }

    private Connection getConnection() throws ServletException {
        Connection conn = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/bookdb";
            String username = "root";
            String password = "root";
            conn = DriverManager.getConnection(url, username, password);
        } catch (ClassNotFoundException e) {
            throw new ServletException(e);
        } catch (SQLException e) {
            throw new ServletException(e);
        }
        return conn;
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");
        if (action == null) {
            action = "list";
        }

        switch (action) {
            case "list":
                listBooks(request, response);
                break;
            case "show":
                showBook(request, response);
                break;
            case "add":
                addBook(request, response);
                break;
            case "edit":
                editBook(request, response);
                break;
            case "update":
                updateBook(request, response);
                break;
            case "delete":
                deleteBook(request, response);
                break;
            default:
                listBooks(request, response);
        }
    }

    private void listBooks(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            List<Book> books = bookDAO.getAllBooks();
            request.setAttribute("books", books);
            RequestDispatcher dispatcher = request.getRequestDispatcher("/book_list.jsp");
            dispatcher.forward(request, response);
        } catch (SQLException e) {
            throw new ServletException(e);
        }
    }

    private void showBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String bookId = request.getParameter("bookId");
        try {
            Book book = bookDAO.getBookById(bookId);
            request.setAttribute("book", book);
            RequestDispatcher dispatcher = request.getRequestDispatcher("/book_show.jsp");
            dispatcher.forward(request, response);
        } catch (SQLException e) {
            throw new ServletException(e);
        }
    }

    private void addBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String bookId = request.getParameter("bookId");
        String bookName = request.getParameter("bookName");
        String author = request.getParameter("author");
        double price = Double.parseDouble(request.getParameter("price"));
        Book book = new Book();
        book.setBookId(bookId);
        book.setBookName(bookName);
        book.setAuthor(author);
        book.setPrice(price);
        try {
            bookDAO.addBook(book);
            response.sendRedirect("BookServlet");
        } catch (SQLException e) {
            throw new ServletException(e);
        }
    }

    private void editBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String bookId = request.getParameter("bookId");
        try {
            Book book = bookDAO.getBookById(bookId);
            request.setAttribute("book", book);
            RequestDispatcher dispatcher = request.getRequestDispatcher("/book_edit.jsp");
            dispatcher.forward(request, response);
        } catch (SQLException e) {
            throw new ServletException(e);
        }
    }

    private void updateBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String bookId = request.getParameter("bookId");
        String bookName = request.getParameter("bookName");
        String author = request.getParameter("author");
        double price = Double.parseDouble(request.getParameter("price"));
        Book book = new Book();
        book.setBookId(bookId);
        book.setBookName(bookName);
        book.setAuthor(author);
        book.setPrice(price);
        try {
            bookDAO.updateBook(book);
            response.sendRedirect("BookServlet");
        } catch (SQLException e) {
            throw new ServletException(e);
        }
    }

    private void deleteBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String bookId = request.getParameter("bookId");
        try {
            bookDAO.deleteBook(bookId);
            response.sendRedirect("BookServlet");
        } catch (SQLException e) {
            throw new ServletException(e);
        }
    }

    public void destroy() {
        try {
            conn.close(); // 关闭数据库连接
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

以上就是一个基本的图书管理系统的设计和实现。当用户发送HTTP请求时，BookServlet会调用相应的DAO方法来处理请求，并将处理结果通过JSP页面呈现给用户。