@WebServlet(name = "C_AddServlet", value = "/C_AddServlet") public class C_AddServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); String id_clazz = request.getParameter("id_clazz"); String college = request.getParameter("college"); String major = request.getParameter("major"); Integer grade = Integer.parseInt(request.getParameter("grade")); Integer no = Integer.parseInt(request.getParameter("no")); String id_teacher = request.getParameter("id_teacher"); Clazz clazz = new Clazz(id_clazz,college,major,grade,no,id_teacher); ClazzService clazzService = new ClazzService(); try { clazzService.save(clazz); } catch (Exception e) { if (e.getClass().equals(SQLIntegrityConstraintViolationException.class)){ System.out.println("该班级号已存在！"); }else { e.printStackTrace(); } } response.sendRedirect("ListServlet"); } }

这段代码是一个Java Servlet，用来处理添加班级的请求。具体来说，代码中的@WebServlet注解用来指定Servlet的名称和URL，这里的名称为C_AddServlet，URL为/C_AddServlet。

代码中的doGet()方法和doPost()方法分别用来处理GET请求和POST请求。这里的doGet()方法直接调用doPost()方法进行处理，因此这个Servlet只接受POST请求。

在doPost()方法中，代码首先设置请求的字符编码为utf-8，然后通过request.getParameter()方法获取表单中提交的各个参数，包括id_clazz（班级ID）、college（学院）、major（专业）、grade（年级）、no（班级号）和id_teacher（班主任ID）。

接着，代码将这些参数封装成一个Clazz对象，并将其保存到数据库中，具体的保存操作由ClazzService类的save()方法实现。

如果保存过程中出现异常，代码会判断异常的类型，如果是SQLIntegrityConstraintViolationException类型，说明班级号已经存在，代码会输出提示信息。否则，代码会打印异常的堆栈信息。

最后，代码通过response.sendRedirect()方法将请求重定向到ListServlet，从而显示班级列表。

相关问题

@WebServlet(name = "deleteServlet", value = "/deleteServlet") public class deleteServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doGet(request,response); } }在这个页面填好

这个 Servlet 是一个空实现，需要根据具体需求进行修改。以下是一个简单的删除操作的示例：

@WebServlet(name = "deleteServlet", value = "/deleteServlet")
public class deleteServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String id = request.getParameter("id");
        // 根据具体需求进行删除操作，以下是一个示例代码
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            conn = DBUtil.getConnection();
            String sql = "DELETE FROM user WHERE id = ?";
            ps = conn.prepareStatement(sql);
            ps.setString(1, id);
            ps.executeUpdate();
            response.sendRedirect("userList.jsp");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, ps, null);
        }
    }
}

该 Servlet 接收一个 POST 请求，从请求参数中获取一个 `id` 值，然后连接数据库，执行 SQL 语句删除对应的行，并重定向到用户列表页。需要注意的是，这里使用了一个 DBUtil 类来获取数据库连接和关闭资源，可以根据自己的情况进行修改。另外，需要将 SQL 语句中的 `user` 替换成实际的表名。

import jakarta.servlet.*; import jakarta.servlet.http.*; import jakarta.servlet.annotation.*; import java.io.IOException; @WebServlet(name = "ForwordServlet", value = "/ForwordServlet") public class ForwordServlet extends HttpServlet{ @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); request.setAttribute("usernamer","张三"); RequsetDispatcher dispatcher = request.getRequestDispatcher("/ResultServlet"); dispatcher.forward(request,response); } @Override protected void doPost这段代码的RequestDispacher错误怎么解决(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }

这段代码中的错误在于"RequsetDispatcher"拼写错误，应为"RequestDispatcher"。正确的代码应该是:

import jakarta.servlet.*;
import jakarta.servlet.http.*;
import jakarta.servlet.annotation.*;
import java.io.IOException;

@WebServlet(name = "ForwordServlet", value = "/ForwordServlet")
public class ForwordServlet extends HttpServlet{

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
request.setAttribute("usernamer","张三");
RequestDispatcher dispatcher = request.getRequestDispatcher("/ResultServlet");
dispatcher.forward(request,response);
}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}
}