java - 参数索引超出范围(1 > 参数个数，即0)，如何避免？

Question

Java Code

I have been trying to updated the selected row values but Im getting Parameter index out of bound exception. Any suggestions? the statement is correct, also can anyone explain in why it occurs?

public class Editbook extends HttpServlet {
    private static final long serialVersionUID = 1L;
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        PrintWriter out = response.getWriter();
        try {
            String booktitle = request.getParameter("booktitle");
            String author = request.getParameter("author");
            String category = request.getParameter("category");
            String pages = request.getParameter("pages");
            String desc = request.getParameter("description");
            String isbn = request.getParameter("isbn");

            Connection con = Logincheck.getConnection();
            PreparedStatement ps = con.prepareStatement("update books set title ='"+booktitle+"', author ='"+author+"', category ='"+category+"', pages ='"+pages+"', description ='"+desc+"' where isbn ='"+isbn+"'");

            ps.setInt(1, Integer.parseInt(isbn));
            ps.setString(2, booktitle);
            ps.setString(3, author);
            ps.setString(4, category);
            ps.setInt(5, Integer.parseInt(pages));
            ps.setString(6, desc);

            int i = ps.executeUpdate();
            out.println("updated");
            System.out.println(i + "updated");
        } catch (Exception e) {System.out.println(e);}

    }

}

Answer 1

在PreparedStatement中，您直接输入参数值，而不使用任何?。所以当你写

 ps.setInt(1, Integer.parseInt(isbn));

该语句将第一次出现的 ? 替换为指定值。但由于没有?，它会给出参数索引超出范围的异常。