修改图书(Servlet: EditBookServlet) 在这个Servlet中，需要通过JDBC连接数据库，查询出要修改的图书的信息，并且展示到editBook.jsp页面上。用户修改完成后，需要将修改后的图书信息更新到数据库中，并且需要对用户输入的数据进行合法性验证。修改完成后，将结果放入到request中，然后转发到bookList.jsp页面展示。给我代码

以下是 EditBookServlet 的代码：

import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/EditBookServlet")
public class EditBookServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        int bookId = Integer.parseInt(request.getParameter("bookId"));
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        try {
            conn = DBUtil.getConnection();
            String sql = "SELECT * FROM book WHERE book_id=?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, bookId);
            rs = pstmt.executeQuery();
            if (rs.next()) {
                Book book = new Book();
                book.setId(rs.getInt("book_id"));
                book.setTitle(rs.getString("title"));
                book.setAuthor(rs.getString("author"));
                book.setPrice(rs.getDouble("price"));
                request.setAttribute("book", book);
                request.getRequestDispatcher("/editBook.jsp").forward(request, response);
            } else {
                response.sendRedirect(request.getContextPath() + "/bookList.jsp");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(rs, pstmt, conn);
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        int bookId = Integer.parseInt(request.getParameter("bookId"));
        String title = request.getParameter("title");
        String author = request.getParameter("author");
        String priceStr = request.getParameter("price");
        double price = 0.0;
        if (priceStr != null && !priceStr.isEmpty()) {
            price = Double.parseDouble(priceStr);
        }

        // 合法性验证
        if (title == null || title.isEmpty()) {
            request.setAttribute("errorMsg", "图书名称不能为空");
            request.getRequestDispatcher("/editBook.jsp").forward(request, response);
            return;
        }
        if (author == null || author.isEmpty()) {
            request.setAttribute("errorMsg", "作者名称不能为空");
            request.getRequestDispatcher("/editBook.jsp").forward(request, response);
            return;
        }
        if (price <= 0) {
            request.setAttribute("errorMsg", "价格必须大于0");
            request.getRequestDispatcher("/editBook.jsp").forward(request, response);
            return;
        }

        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            conn = DBUtil.getConnection();
            String sql = "UPDATE book SET title=?, author=?, price=? WHERE book_id=?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, title);
            pstmt.setString(2, author);
            pstmt.setDouble(3, price);
            pstmt.setInt(4, bookId);
            int result = pstmt.executeUpdate();
            if (result > 0) {
                request.setAttribute("successMsg", "修改成功");
            } else {
                request.setAttribute("errorMsg", "修改失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
            request.setAttribute("errorMsg", "修改失败");
        } finally {
            DBUtil.close(pstmt, conn);
        }
        request.getRequestDispatcher("/bookList.jsp").forward(request, response);
    }
}

注：以上代码中的 `DBUtil` 类封装了数据库连接的方法。