老师，我这里报错帮忙看看

package com.imooc.mgallery.utils;

import java.io.UnsupportedEncodingException;

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.mgallery.entity.Painting;

* 数据源类

public class XmlDatasource {

//通过static保证数据唯一

private static List<Painting> data=new ArrayList();

private static String dataFile;

static {

dataFile=XmlDatasource.class.getResource("/painting.xml").getPath();

URLDecoder decoder=new URLDecoder();

try {

dataFile=decoder.decode(dataFile,"uft-8");

//System.out.println(dataFile);

//dom4j 解析

SAXReader reader=new SAXReader();

//获取文档对象

Document document=reader.read(dataFile);

//得到xml节点

List<Node> nodes=document.selectNodes("/root/painting");

//遍历node节点

for(Node node:nodes) {

Element element=(Element)node;

String id=element.attributeValue("id");

String pan=element.elementText("pname");

Painting painting=new Painting();

painting.setId(Integer.parseInt(id));

painting.setPname(pan);

painting.setCategroy(Integer.parseInt(element.elementText("category")));

painting.setPrice(Integer.parseInt(element.elementText("price")));

painting.setPreview(element.elementText("preview"));

painting.setDecription(element.elementText("description"));

data.add(painting);

// System.out.println(id+""+pan);

}

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

public static List<Painting> getRawData(){

return data;

}

public static void main(String[] args) {

// new XmlDatasource();

List <Painting> ps=XmlDatasource.getRawData();

System.out.println(ps);

}

package com.imooc.mgallery.utils;

import java.util.ArrayList;

import java.util.List;

public class PageModel {

private int paga;//页号

private int totalPages;//页总数

private int rows;//每页记录

private int totalRows;//总记录数

private int pageStartRow;//当前页从第N行开始

private int pageEndRow;//当前页从第N行结束

private boolean hasNextPage;//是否存在下一页

private boolean hasPreviousPage;//是否存在上一页

private List pageData;//当前页数据

public PageModel() {

}

/**

* 初始化对象

* @param Data 原来数据集合

* @param paga 页号

* @param rows 每页计数

public PageModel(List data,int paga,int rows) {

this.paga=paga;

this.rows=rows;

totalRows=data.size();

totalPages=new Double(Math.ceil(pageEndRow/(rows*1f))).intValue();

if(pageStartRow>pageEndRow) {

pageStartRow=pageEndRow;

}

pageStartRow=(paga-1)*rows;

pageEndRow=paga*rows;

pageData=data.subList(pageStartRow, pageEndRow);

if(paga>1) {

hasPreviousPage = true;

}else {

hasPreviousPage = false;

}

if(paga<totalPages) {

hasNextPage=true;

}else {

hasNextPage=false;

}

public int getPaga() {

return paga;

}

public void setPaga(int paga) {

this.paga = paga;

}

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 list=new ArrayList();

for(int i=0;i<=100;i++) {

list.add(i);

}

PageModel pa=new PageModel(list,6,8);

System.out.println(pa.getPageData());

System.out.println(pa.getTotalPages());

System.out.println(pa.getPageEndRow()+":"+pa.getPageStartRow());

}

package com.imooc.mgallery.dao;

import java.util.List;

import com.imooc.mgallery.entity.Painting;

import com.imooc.mgallery.utils.PageModel;

import com.imooc.mgallery.utils.XmlDatasource;

public class PainTingDao {

public PageModel pagination(int paga,int rows) {

List<Painting> list =XmlDatasource.getRawData();

PageModel pa=new PageModel(list,paga,rows);

return pa;

}

package com.imooc.mgallery.service;

import java.util.List;

import com.imooc.mgallery.dao.PainTingDao;

import com.imooc.mgallery.entity.Painting;

import com.imooc.mgallery.utils.PageModel;

public class PaintingService {

private PainTingDao dao=new PainTingDao();

public PageModel pagination(int paga,int rows) {

if(rows==0) {

throw new RuntimeException("无效的参数");

}

return dao.pagination(paga, rows);

}

public static void main(String[] args) {

PaintingService Pa=new PaintingService();

PageModel pp=Pa.pagination(3, 5);

List<Painting> PaintingList=pp.getPageData();

for(Painting pa :PaintingList) {

System.out.println(pa.getPname());

}

System.out.println(pp.getPageStartRow()+":"+pp.getPageEndRow());

}

package com.imooc.mgallery.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.mgallery.service.PaintingService;

import com.imooc.mgallery.utils.PageModel;

/**

* Servlet implementation class Paintingcontroller

@WebServlet("/pa")

public class Paintingcontroller extends HttpServlet {

private static final long serialVersionUID = 1L;

private PaintingService pa=new PaintingService();

/**

* @see HttpServlet#HttpServlet()

public Paintingcontroller() {

super();

// TODO Auto-generated constructor stub

}

/**

* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

String paga=request.getParameter("p");

String rows=request.getParameter("r");

if(paga==null) {

paga="1";

}

if(rows==null) {

rows="6";

}

PageModel md=pa.pagination(Integer.parseInt(paga),Integer.parseInt(rows));

request.setAttribute("md", md);

request.getRequestDispatcher("WEB-INF/jsp/index.jsp").forward(request, response);;

}

<%@page contentType="text/html;charset=UTF-8"%>

<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<%@taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>

<!DOCTYPE html>

<html>

<head>

<title>Document</title>

</head>

<body>

</div>

</ul>

</div>

<ul>

</ul>

</div>

</div>

<ul>

<c:forEach items="${md.pagaData}" var="painting">

<li>

<h3>${painting.pname}</h3>

<p>

${painting.description }

</p>

</div>

</a>

</div>

</li>

</c:forEach>

</ul>

</div>

<ul>

</ul>

</div>

</div>

</body>

</html>

热爱编程学习 2021-01-18

源自：企业门户网站前后台开发 3-3 实现油画数据分页展示

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1回答

好帮手慕阿园 2021-01-18 13:45:48

同学你好，是哪里报错呢，建议同学将报错信息进行反馈，便于老师定位问题；并且建议同学描述是做了什么样的操作后报错呢

祝学习愉快~

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提问者热爱编程学习 #1

2021-01-18 18:24:35
提问者热爱编程学习 #2

老师这里是什么问题？

2021-01-18 18:25:03
好帮手慕阿园回复提问者热爱编程学习 #3

同学你好，根据报错信息是在PaintingService的第18行出现了错误，拼接测试代码没有出现同学这样的错误
错误信息表示在Integer.parseInt()转换时参数是null，所以也就无法转换为Integer类型了
建议同学检查下报错位置处的代码，同学可以下载源码运行试试，并且进行对照
如果还有问题建议同学指出Service18行和controller的42行代码
祝学习愉快~

2021-01-18 19:29:26