今天写极限测试写了好久，随便交一个servlet类

package com.example.limittest01;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

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

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

        // 获取表单提交的数据
        String jobID = request.getParameter("jobID");
        String name = request.getParameter("name");
        String sex = request.getParameter("sex");
        String birthday = request.getParameter("birthday");
        String department = request.getParameter("department");
        String role = request.getParameter("role");

        Connection connection = null;
        PreparedStatement preparedStatement = null;

        // 验证工号是否唯一
        if (!isJobIDUnique(jobID)) {
            out.println("工号已存在，添加失败");
            return;
        }

        // 如果选择的身份是经理，检查部门中是否已经有经理
        if ("manager".equals(role) && isDepartmentManagerExists(department)) {
            out.println("所选部门已有经理，不允许添加新的经理");
            return;
        }

        try {
            // 获取数据库连接
            connection = DatabaseConnection.getConnection();

            // 执行插入数据的 SQL 语句
            String sql = "INSERT INTO employee (JobID, Name, Sex, Birthday, Department, Role) VALUES (?, ?, ?, ?, ?, ?)";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, jobID);
            preparedStatement.setString(2, name);
            preparedStatement.setString(3, sex);
            preparedStatement.setString(4, birthday);
            preparedStatement.setString(5, department);
            preparedStatement.setString(6, role);

            // 执行 SQL 语句
            int rowsAffected = preparedStatement.executeUpdate();

            if (rowsAffected > 0) {
                // 插入成功
                response.getWriter().print("插入成功");
            } else {
                // 插入失败
                response.getWriter().print("插入失败");
            }
        } catch (SQLException | ClassNotFoundException e) {
            e.printStackTrace();
            // 异常处理，这里可以根据具体情况返回不同的信息
            response.getWriter().print("插入失败，发生异常");
        } finally {
            // 关闭连接和 statement
            try {
                if (preparedStatement != null) {
                    preparedStatement.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        // 插入成功
        out.println("添加成功");
    }

    // 验证工号是否唯一
    private boolean isJobIDUnique(String jobID) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            // 获取数据库连接
            connection = DatabaseConnection.getConnection();

            // 执行查询的 SQL 语句
            String sql = "SELECT COUNT(*) FROM employee WHERE JobID = ?";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, jobID);

            // 执行查询
            resultSet = preparedStatement.executeQuery();

            // 获取查询结果
            if (resultSet.next()) {
                int count = resultSet.getInt(1);
                // 如果 count 大于 0，说明存在相同的工号，返回 false
                return count == 0;
            }
        } catch (SQLException | ClassNotFoundException e) {
            e.printStackTrace();
            // 异常处理，这里可以根据具体情况返回 false
            return false;
        } finally {
            // 关闭连接、statement 和 resultSet
            try {
                if (resultSet != null) {
                    resultSet.close();
                }
                if (preparedStatement != null) {
                    preparedStatement.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        // 默认返回 true
        return true;
    }


    // 检查部门中是否已经有经理
    private boolean isDepartmentManagerExists(String department) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            // 获取数据库连接
            connection = DatabaseConnection.getConnection();

            // 执行查询的 SQL 语句
            String sql = "SELECT COUNT(*) FROM employee WHERE Department = ? AND Role = 'manager'";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, department);

            // 执行查询
            resultSet = preparedStatement.executeQuery();

            // 获取查询结果
            if (resultSet.next()) {
                int count = resultSet.getInt(1);
                // 如果 count 大于 0，说明该部门中已经有经理，返回 true
                return count > 0;
            }
        } catch (SQLException | ClassNotFoundException e) {
            e.printStackTrace();
            // 异常处理，这里可以根据具体情况返回 false
            return false;
        } finally {
            // 关闭连接、statement 和 resultSet
            try {
                if (resultSet != null) {
                    resultSet.close();
                }
                if (preparedStatement != null) {
                    preparedStatement.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        // 默认返回 false
        return false;
    }

}