[求助]这个怎么做添加修改，是MyBatis框架写的文件

package org.fkjava.bookapp.servlet;

import import java.lang.reflect.InvocationTargetException;
import java.util.List;
import java.util.Map;
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 org.import org.fkjava.bookapp.dto.Book;
import org.fkjava.bookapp.service.BookService;
import org.fkjava.bookapp.service.BookServiceImpl;
@WebServlet("/books")
public class BookServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private HttpServletRequest request;
    private HttpServletResponse response;

    private BookService bookService = new BookServiceImpl();

    public BookServlet() {
    }

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

    protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        this.request = request;
        this.response = response;
        String method = request.getParameter("method");
        if ("list".equals(method)) {
            list();
        } else if ("delete".equals(method)) {
            delete();
        } else if ("add".equals(method)) {
            add();
        } else if ("update".equals(method)) {
            update();
        }
    }

    private void update() {
        String id = request.getParameter("id");
        Book book = bookService.findOne(id);
        
        request.setAttribute("book", book);
        try {
            request.getRequestDispatcher("/bookAdd.jsp").forward(request, response);
        } catch (ServletException | IOException e) {
            e.printStackTrace();
        }
    }

    private void add() throws IOException {
        String id = request.getParameter("id");
        if(id!=null){
            delete();
        }
        
        Map<String, String[]> map = request.getParameterMap();
        Book book = new Book();
        try {
            BeanUtils.populate(book, map);
            bookService.add(book);
        } catch (IllegalAccessException | InvocationTargetException e) {
            e.printStackTrace();
        }

    }

    private void delete() {
        try {
            // 接收需要删除的数据id
            String id = request.getParameter("id");
            bookService.deleteById(id);
            request.setAttribute("tip", "删除成功了");
        } catch (Exception e) {
            e.printStackTrace();
            request.setAttribute("tip", "删除异常");
        }
        // 删除成功以后需要回查数据
        list();
    }

    private void list() {
        try {
            // 去查询所有的书本信息
            List<Book> books = bookService.findAll();
            System.out.println(books);
            request.setAttribute("books", books);
            request.getRequestDispatcher("/WEB-INF/jsp/books.jsp").forward(request, response);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

package org.fkjava.bookapp.dao;

import java.util.List;

import org.fkjava.bookapp.dto.Book;

/**

 * @author apple

 * 这个接口是直接操作书这张表的

 *

 * Mybaits接口式编程的核心：mybaits框架 可以为我们的数据访问层接口做实现类

 * 程序员无序自己为数据访问层接口定义实现类。

 *

 */
public interface BookMapper {

    List<Book> selectAll();

    void deleteById(String id);

    void addBook(Book book);

    Book findOne(String id);

}