基于javaweb和数据据写一个简单的图书增删改查代码

好的，以下是一个简单的基于JavaWeb和数据库的图书增删改查代码示例，供您参考：

// 前端JSP界面中的增删改查操作对应着不同的URL请求
@WebServlet("/book")
public class BookServlet extends HttpServlet {

    // 初始化DAO对象
    private BookDao bookDao = new BookDao();

    // 处理GET请求，即展示所有图书信息
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<Book> books = bookDao.getAllBooks(); // 获取所有图书信息
        request.setAttribute("books", books); // 设置请求属性
        request.getRequestDispatcher("book.jsp").forward(request, response); // 转发JSP界面
    }

    // 处理POST请求，即操作图书信息
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取操作类型
        String action = request.getParameter("action");
        if (action == null) { // 如果未指定操作类型，则返回错误信息
            response.getWriter().println("Invalid Request!");
            return;
        }
        
        if (action.equals("add")) { // 添加图书信息
            String name = request.getParameter("name");
            String author = request.getParameter("author");
            int price = Integer.parseInt(request.getParameter("price"));
            int inventory = Integer.parseInt(request.getParameter("inventory"));
            bookDao.addBook(new Book(name, author, price, inventory)); // 调用DAO对象的添加方法
        } else if (action.equals("delete")) { // 删除图书信息
            int id = Integer.parseInt(request.getParameter("id"));
            bookDao.deleteBook(id); // 调用DAO对象的删除方法
        } else if (action.equals("update")) { // 更新图书信息
            int id = Integer.parseInt(request.getParameter("id"));
            String name = request.getParameter("name");
            String author = request.getParameter("author");
            int price = Integer.parseInt(request.getParameter("price"));
            int inventory = Integer.parseInt(request.getParameter("inventory"));
            bookDao.updateBook(new Book(id, name, author, price, inventory)); // 调用DAO对象的更新方法
        } else { // 如果操作类型无效，则返回错误信息
            response.getWriter().println("Invalid Action: " + action);
            return;
        }
        
        response.sendRedirect("book"); // 重定向GET请求，展示所有图书信息
    }

}

其中，DAO对象是负责与数据库交互的数据访问层，示例代码如下：

public class BookDao {

    // 数据库连接信息
    private static final String DRIVER = "com.mysql.jdbc.Driver";
    private static final String URL = "jdbc:mysql://localhost:3306/library";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "password";

    static { // 在加载DAO类时，自动加载数据库驱动
        try {
            Class.forName(DRIVER);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    // 获取所有图书信息
    public List<Book> getAllBooks() {
        List<Book> books = new ArrayList<>();
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
            stmt = conn.createStatement();
            rs = stmt.executeQuery("SELECT * FROM book");
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                String author = rs.getString("author");
                int price = rs.getInt("price");
                int inventory = rs.getInt("inventory");
                books.add(new Book(id, name, author, price, inventory));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                }
                if (stmt != null) {
                    stmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return books;
    }

    // 根据ID号获取图书信息
    public Book getBook(int id) {
        Book book = null;
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        try {
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
            pstmt = conn.prepareStatement("SELECT * FROM book WHERE id = ?");
            pstmt.setInt(1, id);
            rs = pstmt.executeQuery();
            if (rs.next()) {
                String name = rs.getString("name");
                String author = rs.getString("author");
                int price = rs.getInt("price");
                int inventory = rs.getInt("inventory");
                book = new Book(id, name, author, price, inventory);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                }
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return book;
    }

    // 添加新图书信息
    public void addBook(Book book) {
        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
            pstmt = conn.prepareStatement("INSERT INTO book (name, author, price, inventory) VALUES (?, ?, ?, ?)");
            pstmt.setString(1, book.getName());
            pstmt.setString(2, book.getAuthor());
            pstmt.setInt(3, book.getPrice());
            pstmt.setInt(4, book.getInventory());
            pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    // 删除图书信息
    public void deleteBook(int id) {
        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
            pstmt = conn.prepareStatement("DELETE FROM book WHERE id = ?");
            pstmt.setInt(1, id);
            pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    // 更新图书信息
    public void updateBook(Book book) {
        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
            pstmt = conn.prepareStatement("UPDATE book SET name = ?, author = ?, price = ?, inventory = ? WHERE id = ?");
            pstmt.setString(1, book.getName());
            pstmt.setString(2, book.getAuthor());
            pstmt.setInt(3, book.getPrice());
            pstmt.setInt(4, book.getInventory());
            pstmt.setInt(5, book.getId());
            pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

}

以上就是一个简单的基于JavaWeb和数据库的图书增删改查代码示例，希望对您有所帮助！