帮忙看下问题提示 ,还有功能上的

问题描述：

严重: 异常将上下文初始化事件发送到类的侦听器实例.[com.imooc.manage.entity.InitListener]
java.lang.ExceptionInInitializerError
    at com.imooc.manage.entity.InitListener.contextInitialized(InitListener.java:22)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4705)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5171)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1412)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1402)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
    at com.imooc.manage.utils.XmlDataSource.<clinit>(XmlDataSource.java:35)
    ... 10 more

四月 22, 2021 5:16:49 下午 org.apache.catalina.core.StandardContext startInternal
严重: 一个或多个listeners启动失败，更多详细信息查看对应的容器日志文件
四月 22, 2021 5:16:49 下午 org.apache.catalina.core.StandardContext startInternal
严重: 由于之前的错误，Context[]启动失败

相关代码：

package com.imooc.manage.controller;

import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.UUID;

import javax.servlet.ServletContext;
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.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import com.imooc.manage.entity.Book;
import com.imooc.manage.entity.Category;
import com.imooc.manage.entity.User;
import com.imooc.manage.service.BookServiceImpl;
import com.imooc.manage.service.CategoryServiceImpl;
import com.imooc.manage.service.UserServiceImpl;
import com.imooc.manage.utils.PageModel;

/**
 * Servlet implementation class ManageController
 */
@WebServlet("/management")
public class ManageController extends HttpServlet {
    private BookServiceImpl bookService=new BookServiceImpl();
    private CategoryServiceImpl categoryService=new CategoryServiceImpl();
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public ManageController() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=utf-8");
        List<Book> bookData=(List)bookService.pagination(2,6);
        request.setAttribute("bookData", bookData);
        List<Category> categoryData =(List) categoryService.pagination(2,3);
          request.setAttribute("categoryData", categoryData);
        String method=request.getParameter("method");
        if(method.equals("bookList")) {
            this.bookList(request,response);
        }else if(method.equals("deleteBook")) {
            //this.delete(request,response);
        }else if(method.equals("show_create")) {
            this.showCreatePage(request,response);
        }else if(method.equals("show_update")) {
            this.showUpdatePage(request,response);
        }else if(method.equals("categoryList")) {
            this.categoryList(request, response);
        }else if(method.equals("createCategory")) {
            this.createCategory(request,response);
        }else if(method.equals("login")) {
            this.login(request,response);
        }
//        }else if(method.equals(deleteCategory)) {
//            this.deleteCategory(request,response);
//        }else if(method.equals("update")) {
//            
//        }
//            
    }
    public void login(HttpServletRequest request,HttpServletResponse response) {
        String userName=request.getParameter("userName");
        String password=request.getParameter("password");
//        HttpSession session=request.getSession();
//        session.setAttribute("loginUser", userName);
        User user=new User(userName,password);
        ServletContext servletContext=request.getServletContext();
        List<User> userList=(List<User>) servletContext.getAttribute("userList");
        UserServiceImpl userService=new UserServiceImpl();
        if(userService.login(userList, user)==1) {
        request.getSession().setAttribute("user", user);
        try {
        request.getRequestDispatcher("/WEB-INF/jsp/bookList.jsp").forward(request, response);
        } catch (ServletException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        }
        }else {
        try {
        request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);
        } catch (ServletException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        }
        }
        } 


    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

//    private void addBook(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//          request.getRequestDispatcher("/WEB-INF/jsp/addBook.jsp").forward(request, response);
//     }
    //显示分类管理页面
    public void categoryList(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
        request.getRequestDispatcher("/WEB-INF/jsp/categoryList.jsp").forward(request, response);
    }

    //显示图书
    private void bookList(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
        String  p=request.getParameter("p");
        String r=request.getParameter("r");
        if(p==null) {
            p="2";
        }
        if(r==null) {
            r="6";

            }

        PageModel pageModel=bookService.pagination(Integer.parseInt(p),Integer.parseInt(r));
        request.setAttribute("pageModel", pageModel);
        request.getRequestDispatcher("WEB-INF/jsp/bookList.jsp").forward(request,response);
    }
    //显示新增图书页面
    public void showCreatePage(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
        request.getRequestDispatcher("WEB-INF/jsp/addBook.jsp").forward(request, response);

    }
    //新增图书
    public void createBook(HttpServletRequest request,HttpServletResponse response) {
//        String bname=request.getParameter("bname");
//        System.out.println(bname);
    //    request.getRequestDispatcher("/WEB-INF/jsp/addBook.jsp").forward(request, response);
        //初始化Fileupload组件
        FileItemFactory factory=new DiskFileItemFactory();

        ServletFileUpload sf=new ServletFileUpload(factory);
        //遍历FileItem
        List<FileItem> formData;
        try {
            formData = sf.parseRequest(request);
            Book book=new Book();
        for(FileItem fi:formData) {
            if(fi.isFormField()) {
                System.out.println("普通输入项:"+fi.getFieldName()+":"+fi.getString("UTF-8"));
                switch(fi.getFieldName()) {
                case "bookName":
                    book.setBookName(fi.getString("UTF-8"));
                    break;
                case "category":
                    book.setCategory(fi.getString("UTF-8"));
                    break;
                case "price":
                    book.setPrice(Integer.parseInt(fi.getString("UTF-8")));
                    break;

                case "remarks":
                    book.setRemarks(fi.getString("UTF-8"));
                    break;
                default:
                    break;
                }
            }else {
                System.out.println("文件上传项:"+fi.getFieldName());
                //文件保存到服务器目录
                String path=request.getServletContext().getRealPath("/upload");
                        System.out.println("文件上传目录:"+path);
                String fileName=UUID.randomUUID().toString();
                String suffix=fi.getName().substring(fi.getName().lastIndexOf("."));
                fi.write(new File(path,fileName+suffix));
                book.setBookPic("/upload"+fileName+suffix);

            }
        }
        bookService.addBook(book);//新增书籍功能
        response.sendRedirect("/management?method=bookList");//返回列表页

        }catch(Exception e){
            e.printStackTrace();
        }

        }
    public void createCategory(HttpServletRequest request,HttpServletResponse response) throws IOException {
        FileItemFactory factory=new DiskFileItemFactory();
        //将前端表单数据转换为FileItem对象
        ServletFileUpload sf=new ServletFileUpload(factory);
        //用于为FileUpload组件提供java web层面上的http请求解析,增加对web的支持。
          try {
           List<FileItem> formData = sf.parseRequest(request);
           Category category = new Category();
           for(FileItem fi : formData) {
            if(fi.isFormField()) {
             switch (fi.getFieldName()) {   //用于处理普通文本框
             case "categoryId":
              category.setCategoryId(fi.getString("UTF-8"));
              break;
             case "categoryName":
                 category.setCategoryName(fi.getString("UTF-8"));
                 break;
             default:
              break;
             }
            }
           }
           categoryService.addCategory(category);//此为新增功能，层层调用，controller，service，xmlData。
           response.sendRedirect("/categoryList.jsp");//在填完表单之后返回
          }catch(FileUploadException e) {
           e.printStackTrace();
          }
         }
    //按类别查询图书
    public void search(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
        String categoryName=request.getParameter("searchContent");

        List<Book> bookData=bookService.getBooksByCatgoryName(categoryName);
        request.getServletContext().setAttribute("bookData", bookData);
        List<Category> categoryData=(List)categoryService.pagination(2, 3);
        request.getServletContext().setAttribute("categoryData", categoryData);
        request.setAttribute("searchContent", categoryName);
        request.getRequestDispatcher("/WEB-INF/jsp/bookList.jsp").forward(request, response);
    }
        //显示更新页面
    private void showUpdatePage(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
        String id=request.getParameter("bookId");
        Book book=bookService.getBooksById(id);
        request.setAttribute("book", book);
        request.getRequestDispatcher("/WEB-INF/jsp/updateBook.jsp").forward(request,response);

    }

    }


    Book Controller:

package com.imooc.manage.controller;

import java.io.IOException;
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 com.imooc.manage.service.BookServiceImpl;
import com.imooc.manage.utils.PageModel;

/**
 * Servlet implementation class BookController
 */
@WebServlet("/pagecontro")
public class BookController extends HttpServlet {
    private static final long serialVersionUID = 1L;
  private BookServiceImpl bookService=new BookServiceImpl();     
    /**
     * @see HttpServlet#HttpServlet()
     */
    public BookController() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        String page=request.getParameter("p");
        String rows=request.getParameter("r");

        if(page==null) {
            page="2";

        }
        if(rows==null) {
            rows="6";
        }

        PageModel pageModel=bookService.pagination(Integer.parseInt(page),Integer.parseInt(rows));
    request.setAttribute("pageModel", pageModel);
    request.getRequestDispatcher("/WEB-INF/jsp/bookList.jsp").forward(request, response);
    }

}

BookDao:
package com.imooc.manage.dao;

import java.util.List;

import com.imooc.manage.entity.Book;
import com.imooc.manage.utils.PageModel;
import com.imooc.manage.utils.XmlDataSource;

public class BookDao {
    //页面展示图书信息,通过XmlDataSource文件进行读取
    public PageModel pagination(int page,int rows) {
    List<Book> list=XmlDataSource.getBooks();
    PageModel pageModel=new PageModel(list,page,rows);
    return pageModel;
    }
    //新增图书
    public void addBook(Book book) {
        XmlDataSource.appendBook(book);
    }
    //通过bookId查找图书
    public Book getBooksById(String bookId) {
        List<Book> bookData=XmlDataSource.getBooks();
        Book book=null;
        for(Book b:bookData) {
            if(b.getBookId()==Integer.parseInt(bookId)) {
                book=b;
                break;
            }
        }
        return book;
    }
    //按categoryName查找图书
//    public Book getBooksByCategoryName(String categoryName) {
//        XmlDataSource.getBooksByCategoryName(categoryName);
//    }
  //删除图书
    public void deleteBook(Integer id) {
        XmlDataSource.deleteBook(id);
    }
    //更新图书
    public void updateBook(Book book) {
        XmlDataSource.updateBook(book);
    }
}

​categoryDao:
​package com.imooc.manage.dao;

import java.util.List;


import com.imooc.manage.entity.Category;
import com.imooc.manage.utils.PageModel;
import com.imooc.manage.utils.XmlDataSource;

public class CategoryDao {
     public PageModel pagination(int page,int rows) {
            List<Category> list=XmlDataSource.getCategorys();
            PageModel pageModel=new PageModel(list,page,rows);
            return pageModel;
            }
     public void addCategory(Category category) {
          XmlDataSource.appendCategory(category);
      }
      public void deleteCategory(String id) {
          XmlDataSource.deleteCategory(id);
      }
}
​
userDao:
​package com.imooc.manage.dao;

import java.util.List;


import com.imooc.manage.entity.User;
import com.imooc.manage.utils.PageModel;
import com.imooc.manage.utils.XmlDataSource;

public class UserDao {
     public PageModel pagination(int page,int rows) {
            List<User> listUser=XmlDataSource.getUsers();
            PageModel pageModel=new PageModel(listUser,page,rows);
            return pageModel;
            }
}

AuthFilter:
package com.imooc.manage.entity;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class AuthFilter implements Filter{

    @Override
    public void destroy() {
        // TODO Auto-generated method stub

    }

    @Override
    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain chain)
            throws IOException, ServletException {
        // TODO Auto-generated method stub
        HttpServletRequest req=(HttpServletRequest) arg0;
        HttpServletResponse res=(HttpServletResponse) arg1;
        HttpSession session =req.getSession();
        User login=(User) session.getAttribute("login");
        boolean flag=false;
        String reqURI=req.getRequestURI();
        //不需要过滤的url
        String[] url= {".js",".ico",".css",".jsp",".html",".png","/login"};
        for(String str:url) {
            if(reqURI.indexOf(str)!=-1) {
                flag=true;
                break;
            }
        }
        if(!flag) {
            if(login!=null) {
                chain.doFilter(req,res);
                return;
            }else {
                res.sendRedirect(req.getContextPath()+"/login.jsp");
                return;    
            }
        }
        chain.doFilter(req,res);
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub

    }

}
EncodeFilter:
​package com.imooc.manage.entity;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class EncodeFilter implements Filter{

    @Override
    public void destroy() {
        // TODO Auto-generated method stub

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        // TODO Auto-generated method stub
       HttpServletRequest req=(HttpServletRequest)request;
       HttpServletResponse res=(HttpServletResponse)response;
        req.setCharacterEncoding("UTF-8");
        res.setCharacterEncoding("UTF-8");
        chain.doFilter(request,response);
        return;
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub

    }

}

InitListener:
package com.imooc.manage.entity;

import java.util.List;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import com.imooc.manage.utils.XmlDataSource;

public class InitListener implements ServletContextListener{

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        // TODO Auto-generated method stub

    }

    @Override
    public void contextInitialized(ServletContextEvent sre) {
        // TODO Auto-generated method stub

        List<User> userData=XmlDataSource.getUsers();
        sre.getServletContext().setAttribute("listUser",userData);

    }



}

​Book:
​package com.imooc.manage.entity;

public class Book {
  private Integer id;
  private Integer bookId;
  private String bookName;
  private String category;
  private Integer price;
  private String bookPic;
  private String remarks;
 public Book() {

  }
public Book(Integer id,Integer bookId, String bookName,String category, Integer price, String bookPic, String remarks) {
    super();
    this.id=id;
    this.bookId = bookId;
    this.bookName = bookName;
    this.category = category;
    this.price = price;
    this.bookPic = bookPic;
    this.remarks = remarks;
}
public Integer getId() {
    return id;
}
public void setId(Integer id) {
    this.id=id;
}
public Integer getBookId() {
    return bookId;
}
public void setBookId(Integer bookId) {
    this.bookId = bookId;
}
public String getBookName() {
    return bookName;
}
public void setBookName(String bookName) {
    this.bookName = bookName;
}
public String getCategory() {
    return category;
}
public void setCategory(String category) {
    this.category = category;
}
public Integer getPrice() {
    return price;
}
public void setPrice(Integer price) {
    this.price = price;
}
public String getBookPic() {
    return bookPic;
}
public void setBookPic(String bookPic) {
    this.bookPic = bookPic;
}
public String getRemarks() {
    return remarks;
}
public void setRemarks(String remarks) {
    this.remarks = remarks;
}
@Override
public String toString() {
    return "Book [id="+id+",bookId=" + bookId + ", bookName=" + bookName + ", category=" + category + ", price=" + price
            + ", bookPic=" + bookPic + ", remarks=" + remarks + "]";
}

}

Category:
package com.imooc.manage.entity;

public class Category {
  private String categoryId;
  private String categoryName;
  public Category() {

  }
public Category(String categoryId, String categoryName) {
    super();
    this.categoryId = categoryId;
    this.categoryName = categoryName;
}
public String getCategoryId() {
    return categoryId;
}
public void setCategoryId(String categoryId) {
    this.categoryId = categoryId;
}
public String getCategoryName() {
    return categoryName;
}
public void setCategoryName(String categoryName) {
    this.categoryName = categoryName;
}
@Override
public String toString() {
    return "Category [categoryId=" + categoryId + ", categoryName=" + categoryName + "]";
}

}

​
​User:
​package com.imooc.manage.entity;

public class User {
private String userName;
private String password;
public User() {

}
public User(String userName, String password) {
    super();
    this.userName = userName;
    this.password = password;
}
public String getUserName() {
    return userName;
}
public void setUserName(String userName) {
    this.userName = userName;
}
public String getPassword() {
    return password;
}
public void setPassword(String password) {
    this.password = password;
}
@Override
public String toString() {
    return "User [userName=" + userName + ", password=" + password + "]";
}

}

BookServiceImpl:
package com.imooc.manage.service;

import java.util.List;

import com.imooc.manage.dao.BookDao;
import com.imooc.manage.entity.Book;
import com.imooc.manage.entity.Category;
import com.imooc.manage.utils.PageModel;
import com.imooc.manage.utils.XmlDataSource;

public class BookServiceImpl {
   private BookDao bookDao=new BookDao();
   public PageModel pagination(int page,int rows) {
    if(rows==0) {
        throw new RuntimeException("无效的rows参数");
    }
       return bookDao.pagination(page, rows);
   }
   public void addBook(Book book) {
       bookDao.addBook(book);
   }
   public Book getBooksById(String bookId) {
   Book b=bookDao.getBooksById(bookId);
   if(b==null) {
       throw new RuntimeException("[id="+bookId+"]书籍不存在");
   }
   return b;
   }
   public List<Book> getBooksByCatgoryName(String categoryName) {
       List<Category> categoryData=XmlDataSource.getCategorys();
       List<Book> bookData=XmlDataSource.getBooks();
       List<Book> bookList=null;
       for(Book b:bookData) {
       for(Category c:categoryData) {
           if(c.getCategoryName().equals(b.getCategory())) 



           bookList.add(b);
           break;
       }
       break;
   }
       return bookList;
   }
   //删除图书
   public void deleteBook(Integer id) {
       bookDao.deleteBook(id);

//       bookList.remove(book);
   } 
   /**
      * 更新业务
   * @param newBook 新的图书数据
   * @param isPreviewModified 是否修改bookPic属性
   */
   public void update(Book newBook,Integer isPreviewModified) {
       Book oldBook=this.getBooksById(String.valueOf(newBook.getId()));
       oldBook.setBookId(newBook.getBookId());
       oldBook.setBookName(newBook.getBookName());
       oldBook.setPrice(newBook.getPrice());
       oldBook.setRemarks(newBook.getRemarks());
       if(isPreviewModified==1) {
           oldBook.setBookPic(newBook.getBookPic());
       }
       bookDao.updateBook(oldBook);

   }
   public static void main(String[] args) {
       BookServiceImpl bookService=new BookServiceImpl();
      PageModel pageModel= bookService.pagination(2,6);
       List<Book> BookList=pageModel.getPageData();
       for(Book book:BookList) {
           System.out.println(book.getBookName());
       }
       System.out.println(pageModel.getPageStartRow()+":"+pageModel.getPageEndRow());
   }
}

CategoryServiceImpl:
​package com.imooc.manage.service;


import com.imooc.manage.dao.CategoryDao;
import com.imooc.manage.entity.Category;
import com.imooc.manage.utils.PageModel;

public class CategoryServiceImpl {
     private CategoryDao categoryDao=new CategoryDao();
       public PageModel pagination(int page,int rows) {
        if(rows==0) {
            throw new RuntimeException("无效的rows参数");
        }
           return categoryDao.pagination(page, rows);
}

  public void addCategory(Category category) {
      categoryDao.addCategory(category);
  } 
  public void deleteCategory(String categoryId) {
      categoryDao.deleteCategory(categoryId);
  }
}

UserServiceImpl:
​package com.imooc.manage.service;


import java.util.List;

import com.imooc.manage.dao.UserDao;
import com.imooc.manage.entity.User;
/**
 * 验证登录信息
 * @param listUser 用户信息集合
 * @param user 登录的用户
 * @return 用户账号密码匹配成功则返回1，否则返回0
 */
public class UserServiceImpl {
    private UserDao userDao=new UserDao();
     public int login(List<User>  listUser,User user) {
         List<User> listUser1=(List)userDao.pagination(1,1);
         if(user.getUserName()==null||user.getUserName().equals("")) {
            return 0;
        }else if(user.getPassword()==null||user.getPassword().equals("")) {
            return 0;
        }
        for(User user1:listUser) {
            if(user.getUserName().equals(user1.getUserName())&&user.getPassword().equals(user1.getPassword())) {
                return 1;
            }

        }

        return 0;

     }
}


PageModel:

package com.imooc.manage.utils;

import java.util.ArrayList;
import java.util.List;

//分页模型对象
public class PageModel {
private int page;
private int totalPages;
private int rows;
private int totalRows;
private int pageStartRow;
private int pageEndRow;
private boolean hasNextPage;
private boolean hasPreviousPage;
private List pageData;//当前前页面数据
public PageModel() {

}
 public PageModel(List data,int page,int rows) {
     this.page=page;
     this.rows=rows;
     totalRows=data.size();
     totalPages=new Double(Math.ceil(totalRows/(rows*1f))).intValue();
     pageStartRow=(page-1)*rows;
     pageEndRow=page*rows;
     if(pageEndRow>totalRows) {//避免下标越界异常
         pageEndRow=totalRows;
     }
     data.subList(pageStartRow,pageEndRow);//得到分页数据
   if(page>1) {//判断是否有上一页
       hasPreviousPage=true;
   }else {
       hasPreviousPage=false;
   }
   if(page<totalPages) {//判断是否存在下一页
       hasNextPage=true;

   }else {
       hasNextPage=false;
   }

 }
public int getPage() {
    return page;
}
public void setPage(int page) {
    this.page = page;
}
public int getTotalPages() {
    return totalPages;
}
public void setTotalPages(int totalPages) {
    this.totalPages = totalPages;
}
public int getRows() {
    return rows;
}
public void setRows(int rows) {
    this.rows = rows;
}
public int getTotalRows() {
    return totalRows;
}
public void setTotalRows(int totalRows) {
    this.totalRows = totalRows;
}
public int getPageStartRow() {
    return pageStartRow;
}
public void setPageStartRow(int pageStartRow) {
    this.pageStartRow = pageStartRow;
}
public int getPageEndRow() {
    return pageEndRow;
}
public void setPageEndRow(int pageEndRow) {
    this.pageEndRow = pageEndRow;
}
public boolean isHasNextPage() {
    return hasNextPage;
}
public void setHasNextPage(boolean hasNextPage) {
    this.hasNextPage = hasNextPage;
}
public boolean isHasPreviousPage() {
    return hasPreviousPage;
}
public void setHasPreviousPage(boolean hasPreviousPage) {
    this.hasPreviousPage = hasPreviousPage;
}
public List getPageData() {
    return pageData;
}
public void setPageData(List pageData) {
    this.pageData = pageData;
}
 public static void main(String[] args) {
     List sam=new ArrayList();
     for(int i=1;i<=100;i++) {
         sam.add(i);

     }
     PageModel pageModel=new PageModel(sam,6,8);
     System.out.println(pageModel.getPageData());
     System.out.println(pageModel.getTotalPages());
     System.out.println(pageModel.getPageStartRow()+":"+pageModel.getPageEndRow());

 }
}



XmlDataSource:
package com.imooc.manage.utils;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.List;

import org.dom4j.Document;

import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;

import com.imooc.manage.entity.Book;
import com.imooc.manage.entity.Category;
import com.imooc.manage.entity.User;

public class XmlDataSource {
      private static List<User> userData;

      private static List<Category> categoryData;

        private static List<Book> bookData;

        private static String userDataFile;

        private static String categoryDataFile;

        private static String bookDataFile;
        static {
            userData=new ArrayList<User>();
            userDataFile=XmlDataSource.class.getResource("/user.xml").getPath();//获取数据路径
            bookData=new ArrayList<Book>();
            bookDataFile=XmlDataSource.class.getResource("/book.xml").getPath();
            categoryData=new ArrayList<Category>();
            categoryDataFile=XmlDataSource.class.getResource("/category.xml").getPath();
            reloadUser();
            reloadBooks();
            reloadCategory();
        }
        //加载用户信息
        public static void reloadUser() {
            URLDecoder decoder =new URLDecoder();
            try {
                userDataFile=decoder.decode(userDataFile,"UTF-8");//将dataFile用UTF-8编码规定
                System.out.println(userDataFile);
                //利用dom4j对xml文件进行解析
                SAXReader reader =new SAXReader();
                Document document =reader.read(userDataFile);
                //利用Xpath得到节点集合
                List<Node> nodes=document.selectNodes("/root/user");//提取xml文件中的user节点
                userData.clear();
                for(Node node :nodes) {
                    Element element=(Element)node;
                    String id=element.attributeValue("id");
                    String userName=element.elementText("userName");
                    String password=element.elementText("password");
                    User user=new User();
                    user.setUserName(userName);
                    user.setPassword(password);
                    userData.add(user);
                }

            }catch(Exception e) {
                e.printStackTrace();
            }
        }
        //加载分类
        public static void reloadCategory() {
            URLDecoder decoder=new URLDecoder();
            try {
                categoryDataFile=decoder.decode(categoryDataFile,"UTF-8");
                System.out.println(categoryDataFile);
                SAXReader reader=new SAXReader();
                Document document=reader.read(categoryDataFile);
                List<Node> nodes=document.selectNodes("/root/category");
                categoryData.clear();
                for(Node node :nodes) {
                    Element element=(Element)node;
                    Category category=new Category();
                    category.setCategoryId(element.elementText("categoryId"));
                    category.setCategoryName(element.elementText("categoryName"));
                    categoryData.add(category);
                }
            }catch(Exception e){
                e.printStackTrace();
            }
        }
       //book读取 
     public static void reloadBooks() {

        // 通过URLDecoder类将Base64转换成普通字符窜
         //System.out.println(bookDataFile);
         URLDecoder decoder=new URLDecoder();
         try {
        bookDataFile= decoder.decode(bookDataFile,"UTF-8");
         //dom4j对xml解析
         SAXReader reader=new SAXReader();
         Document document=reader.read(bookDataFile);

         List<Node> nodes=document.selectNodes("/root/book");
         //清空集合
         bookData.clear();
         //遍历节点
         for(Node node:nodes) {
             Element element=(Element) node;
             String id=element.attributeValue("id");
             String bname=element.elementText("bname");

             Book book=new Book();
             book.setBookId(Integer.parseInt(id));
             book.setBookName(bname);
             book.setCategory(element.elementText("category"));
             book.setPrice(Integer.parseInt(element.elementText("price")));
             book.setBookPic(element.elementText("bookPic"));
             book.setRemarks(element.elementText("remarks"));
            bookData.add(book);
            // System.out.println(id+":"+bname);
         }
         }catch(Exception e) {
             e.printStackTrace();
         }
      }
      public static List<User> getUsers(){
          return userData;
      }
      public static List<Category> getCategorys(){
          return categoryData;
      }
      public static List<Book> getBooks(){
          return bookData;
      }
      //按id删除类别
      public static void deleteCategory(String id) {
          SAXReader reader=new SAXReader();
          Writer writer=null;
          try {
            Document document=reader.read(categoryDataFile);
            List<Node> categorynode=document.selectNodes("/root/category[@id="+id+"]");
            if(categorynode.size()==0) {
                throw new RuntimeException("id="+id+"分类编号不存在");

            }
            Element c=(Element)categorynode.get(0);
            c.getParent().remove(c);
            writer=new OutputStreamWriter(new FileOutputStream(categoryDataFile),"UTF-8");
            document.write(writer);
          } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            if(writer!=null) {
                try {
                    writer.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            reloadCategory();
        }

      }
      //按id删除图书
      public static void deleteBook(Integer id) {
          SAXReader reader=new SAXReader();
          Writer writer=null;
          try {
          Document doucment=reader.read(bookDataFile);
          List<Node>nodes=doucment.selectNodes("/root/book[@id="+id+"]");
          if(nodes.size()==0) {
          throw new RuntimeException("id="+id+"图书编号不存在");
          }
          Element b=(Element) nodes.get(0);
          b.getParent().remove(b);
          writer=new OutputStreamWriter(new FileOutputStream(bookDataFile),"UTF-8");
          doucment.write(writer);

          } catch (Exception e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
          }finally {
          if(writer!=null) {
          try {
          writer.close();
          } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
          }
          }
          reloadBooks();
          }

          }
      //新增图书
      public static void appendBook(Book book) {
        //通过SAXReader读取xml文档，得到Document
          SAXReader reader=new SAXReader();
          Writer writer=null;
          try {
              Document document=reader.read(bookDataFile);
            //2.创建book.xml的book节点
              Element root=document.getRootElement();
              Element b=root.addElement("book");
              //创建各个节点
              b.addAttribute("id", String.valueOf(bookData.size()+1));
              b.addElement("bookId").setText(String.valueOf(book.getBookId()));
              b.addElement("bookName").setText(book.getBookName());
              b.addElement("category").setText(book.getCategory());
              b.addElement("price").setText(String.valueOf(book.getPrice()));
              b.addElement("bookPic").setText(book.getBookPic());
              b.addElement("remarks").setText(book.getRemarks());
              //转换字符流追加,写入xml
              writer=new OutputStreamWriter(new FileOutputStream(bookDataFile),"UTF-8");
              document.write(writer);
              System.out.println(bookDataFile);
          }catch(Exception e) {
              e.printStackTrace();
          }finally {
              if(writer!=null) {
                  try {
                    writer.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
              }
              reloadBooks();//保证内存中与文件数据一致
          }
      }
      //新增类别
      public  static void appendCategory(Category category) {
          SAXReader reader =new SAXReader();
              Writer writer=null;
              try {
                  Document document=reader.read(categoryDataFile);//读取文本数据
                  Element root=document.getRootElement();
                  Element p=root.addElement("category");
                  p.addAttribute("id", String.valueOf(categoryData.size()+1));
                  p.addElement("categoryId").setText(category.getCategoryId());
                  p.addElement("categoryName").setText(category.getCategoryName());
                  writer=new OutputStreamWriter(new FileOutputStream(categoryDataFile),"UTF-8");
                  document.write(writer);
                  //System.out.println(categoryDataFile);
              }catch(Exception e) {
                  e.printStackTrace();
              }finally {
                  if(writer!=null) {
                      try {
                        writer.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                  }
                  reloadCategory();
              }
      }
      //更改图书
      public static void updateBook(Book book) {
          SAXReader reader=new SAXReader();
          Writer writer=null;
          try {
            Document document=reader.read(bookDataFile);
            //节点路径[@属性名=属性值]
            // /root/book[@id=x]
            List<Node> nodes=document.selectNodes("/root/book[@id="+book.getBookId()+"]");
            if(nodes.size()==0) {
                throw new RuntimeException("id="+book.getBookId()+"编号书籍不存在");

            }
            Element b=(Element)nodes.get(0);
            b.selectSingleNode("bookName").setText(book.getBookName());
            b.selectSingleNode("category").setText(book.getCategory());
            b.selectSingleNode("price").setText(book.getPrice().toString());
            b.selectSingleNode("bookPic").setText(book.getBookPic());
            b.selectSingleNode("Remarks").setText(book.getRemarks());
            writer=new     OutputStreamWriter(new FileOutputStream(bookDataFile),"UTF-8");
            document.write(writer);
            } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            if(writer!=null) {
                try {
                writer.close();
                }catch(Exception e) {
                    e.printStackTrace();
                }
            }
        }
          reloadBooks();
      }
     public static void main(String[] args) {
        // new XmlDataSource();
        // List<Book> bs=XmlDataSource.getBooks();
        // System.out.println(bs);

         //List<Category> cg=XmlDataSource.getCategorys();
         //System.out.println(cg);
         /*Books b=new Books();
         b.setBookId(1000);
         b.setBookName("软件更新");
         b.setCategoryId("计算机");
         b.setBookPrice(100);
         b.setBookPic("/image/g1.jpg");
         b.setRemarks("测试");
         //XmlDataSource.deleteBook(11010);*/
         //Category c=new Category();
         //c.setCategoryId(2);
         //c.setCategoryName("计算机");
         //XmlDataSource.deleteBook(3);
         //List<Books> bk=XmlDataSource.getBooks();
         //System.out.println(bk);
         List<User> u=XmlDataSource.getUsers();
         System.out.println(u);

        // XmlDataSource.appendBook(book);
     }
}
​