求解释解释代码讲的啥

package servlet;

import bean.Student;
import dao.StudentDaoImpl;

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.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

@WebServlet("/addStudent")
public class AddServlet extends HttpServlet {

protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    Student student = new Student();

    int studentID = Integer.parseInt(req.getParameter("studentID"));

    String name = req.getParameter("name");
    int age = Integer.parseInt(req.getParameter("age"));
    String sex = req.getParameter("radio");
    Date birthday = null;

            // String 类型按照 yyyy-MM-dd 的格式转换为 java.util.Date 类
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
    try {
        birthday = simpleDateFormat.parse(req.getParameter("birthday"));
    } catch (ParseException e) {
        e.printStackTrace();
    }

package servlet;

import bean.Student;
import dao.StudentDaoImpl;

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;

@WebServlet("/editStudent")
public class EditServlet extends HttpServlet {

protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    int id = Integer.parseInt(req.getParameter("id"));
    Student student = new StudentDaoImpl().get(id);

    req.setAttribute("student", student);

    req.getRequestDispatcher("/editStudent.jsp").forward(req, resp);
}

}

其中一个功能 ，想知道是怎么实现信息的增加，什么接口啊类啊啥的。每一行讲的都是啥

获取页面提交的姓名，年龄，性别及生日数据，生日转换为yyyy-MM-dd格式。