代码改错：@WebServlet("/update_teacher") public class update_teacher extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); response.setCharacterEncoding("utf-8"); request.setCharacterEncoding("utf-8"); PrintWriter out = response.getWriter(); HttpSession session = request.getSession(); TeacherDao teacherD = new TeacherDao(); String uid = request.getParameter("uid"); String name = request.getParameter("name"); String sex = request.getParameter("sex"); String email = request.getParameter("email"); String password = request.getParameter("password"); try { Teacher teacher = teacherD.updateTeacher(uid, name, sex, email, password); session.setAttribute("info", teacher); out.print("<script>alert(\"保存成功！\");location.href = \"teacher/personal.jsp\";</script>"); } catch (Exception e) { out.print(e); } } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }

这段代码看起来没有明显的错误，但是建议做一些改进：

1. 类名应该以大写字母开头，所以建议将类名 `update_teacher` 改为 `UpdateTeacher`。

2. 在 `catch` 块中，如果出现异常应该将信息打印到日志中而不是直接输出到页面，因为这样可以避免暴露敏感信息。

3. 如果更新教师信息失败，应该给出友好的提示信息。

下面是改进后的代码：

@WebServlet("/update_teacher")
public class UpdateTeacher extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        response.setCharacterEncoding("utf-8");
        request.setCharacterEncoding("utf-8");

        PrintWriter out = response.getWriter();
        HttpSession session = request.getSession();

        TeacherDao teacherDao = new TeacherDao();

        String uid = request.getParameter("uid");
        String name = request.getParameter("name");
        String sex = request.getParameter("sex");
        String email = request.getParameter("email");
        String password = request.getParameter("password");

        try {
            Teacher teacher = teacherDao.updateTeacher(uid, name, sex, email, password);
            session.setAttribute("info", teacher);
            out.print("<script>alert(\"保存成功！\");location.href = \"teacher/personal.jsp\";</script>");
        } catch (Exception e) {
            Logger.getLogger(UpdateTeacher.class.getName()).log(Level.SEVERE, null, e);
            out.print("<script>alert(\"保存失败，请稍后重试！\");location.href = \"teacher/personal.jsp\";</script>");
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
}