ajax好像没有把消息发送到servlet，老师帮忙看一下

# 具体遇到的问题

# 报错信息的截图

# 相关课程内容截图

# 尝试过的解决思路和结果

# 粘贴全部相关代码，切记添加代码注释（请勿截图）

package com.imooc.mgallery.controller;

import java.io.File;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.UUID;

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.alibaba.fastjson.JSON;

import com.imooc.mgallery.entity.Painting;

import com.imooc.mgallery.service.PaintingService;

import com.imooc.mgallery.utils.PageModel;

/**

 * 后台管理功能controller

 * Servlet implementation class ManagementController

 */

@WebServlet("/management")

public class ManagementController extends HttpServlet {

private static final long serialVersionUID = 1L;

    private PaintingService paintingService = new PaintingService();   

    /**

     * @see HttpServlet#HttpServlet()

     */

    public ManagementController() {

        super();

        // TODO Auto-generated constructor stub

    }

/**

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

*/

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

request.setCharacterEncoding("utf-8");

response.setContentType("text/html;charset=utf-8");

//System.out.println(".......................");

String method = request.getParameter("method");

// System.out.println(method);

if (method.equals("list")) {

this.list(request,response);

} else if (method.equals("delete")) {

//System.out.println(".......................");

this.delete(request, response);

} else if(method.equals("show_create")) {

this.showCreatePage(request,response);

} else if(method.equals("create")) {

this.create(request,response);

} else if (method.equals("show_update")) {

this.showUpdatePage(request,response);

} else if (method.equals("update")) {

this.update(request,response);

}

}

/**

* @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 list(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

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

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

if (p == null) {

p = "1";

}

if (r == null) {

r = "6";

}

PageModel pageModel = paintingService.pagination(Integer.parseInt(p), Integer.parseInt(r));

request.setAttribute("pageModel", pageModel);

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

}

//显示新增页面

private void showCreatePage(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

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

}

//新增油画方法

private void create(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

//文件上传时的数据处理与标准表单完全不同

// String pname = request.getParameter("pname");

// System.out.println(pname);

//1. 初始化FileUpload组件

FileItemFactory factory = new DiskFileItemFactory();

/**

* FileItemFactory 用于将前端表单的数据转换为一个个FileItem对象

* ServletFileUpload 则是为FileUpload组件提供Java web的Http请求解析

*/

ServletFileUpload sf = new ServletFileUpload(factory);

//2. 遍历所有FileItem

try {

List<FileItem> formData = sf.parseRequest(request);

Painting painting = new Painting();

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 "pname":

painting.setPname(fi.getString("utf-8"));

break;

case "price":

painting.setPrice(Integer.parseInt(fi.getString("utf-8")));

break;

case "category":

painting.setCategory(Integer.parseInt(fi.getString("utf-8")));

break;

case "description":

painting.setDescription(fi.getString("utf-8"));

break;

default:

break;

}

} else {

System.out.println("文件上传项:" + fi.getFieldName());

//3.文件保存到服务器目录

String path = request.getServletContext().getRealPath("/upload");

System.out.println("上传文件目录:" + path);

//String fileName = "test.jpg";

String fileName = UUID.randomUUID().toString();//生成一个随机的  唯一的文件名

//截取文件名的最后一个 . 后面的所有字符串

String suffix = fi.getName().substring(fi.getName().lastIndexOf("."));

//写入目标文件

//3. 文件保存到服务器目录

fi.write(new File(path, fileName + suffix));

painting.setPreview("/upload/" + fileName + suffix);

}

}

paintingService.create(painting);

response.sendRedirect("/management?method=list");//返回列表页

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

/**

* 显示更新（修改）页面

* @param request

* @param response

* @throws ServletException

* @throws IOException

*/

private void showUpdatePage(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {

String id = request.getParameter("id");

Painting painting = paintingService.findById(Integer.parseInt(id));

request.setAttribute("painting", painting);

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

}

/**

* 执行更新操作

* @param request

* @param response

* @throws IOException 

* @throws ServletException 

*/

private void update(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {

FileItemFactory factory = new DiskFileItemFactory();

ServletFileUpload sf = new ServletFileUpload(factory);

try {

int isPreviewModified = 0;

List<FileItem> formData = sf.parseRequest(request);

Painting painting = new Painting();

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 "pname":

painting.setPname(fi.getString("utf-8"));

break;

case "price":

painting.setPrice(Integer.parseInt(fi.getString("utf-8")));

break;

case "category":

painting.setCategory(Integer.parseInt(fi.getString("utf-8")));

break;

case "description":

painting.setDescription(fi.getString("utf-8"));

break;

case "id":

painting.setId(Integer.parseInt(fi.getString("utf-8")));

break;

case "isPreviewModified":

isPreviewModified = Integer.parseInt(fi.getString("utf-8"));

break;

default:

break;

}

} else {

//System.out.println("文件上传项:" + fi.getFieldName());

if (isPreviewModified == 1) {//文件改变

String path = request.getServletContext().getRealPath("/upload");

//System.out.println("上传文件目录:" + path);

//String fileName = "test.jpg";

String fileName = UUID.randomUUID().toString();//生成一个随机的  唯一的文件名

//截取文件名的最后一个 . 后面的所有字符串

String suffix = fi.getName().substring(fi.getName().lastIndexOf("."));

//写入目标文件

//3. 文件保存到服务器目录

fi.write(new File(path, fileName + suffix));

painting.setPreview("/upload/" + fileName + suffix);

}

}

}

paintingService.update(painting, isPreviewModified);

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

request.getRequestDispatcher("/management.html").forward(request, response);

}

private void delete(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {

// PrintWriter out = response.getWriter();

System.out.println("******************");

try {

Integer id = Integer.parseInt(request.getParameter("id"));

//System.out.println("id:----------------" + id);

paintingService.delete(id);

Map<String, String> msg = new HashMap<String, String>();

msg.put("result", "ok");

// String msg = "{\"result\":\"ok\"}";

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

response.getWriter().print(JSON.toJSONString(msg));

} catch (Exception e) {

// TODO: handle exception

Map<String, String> msg = new HashMap<String, String>();

msg.put("result", e.getMessage());

response.getWriter().print(JSON.toJSONString(msg));

}

//request.getRequestDispatcher("/management.html").forward(request, response);

}

}

在这里输入代码，可通过选择【代码语言】突出显示

//list.jsp

<%@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>

<meta charset="utf-8">

<title>油画列表</title>

<link rel="stylesheet" type="text/css" href="css\list.css">

<script src="js/jquery-3.4.1.min.js" type="text/javascript"></script>

<script src="js/sweetalert2.js" type="text/javascript"></script>

<script type="text/javascript">

function showPreview(previewObj){

var preview = $(previewObj).attr("data-preview");

var pname = $(previewObj).attr("data-pname");

Swal.fire({

title:pname,

html:"<img src='" + preview +"' style='width:361px;height:240px'>",

showCloseButton:true,

showConfirmButton:false

})

}

function del(delObj){

var id = $(delObj).attr("data-id");

var pname = $(delObj).attr("data-pname");

var preview = $(delObj).attr("data-preview");

Swal.fire({

title:"确定要删除[" + pname + "]吗?",

html:"<img src='" + preview + "' style='width:361px;height:240px'>",

showCancelButton:true,

confirmButtonText:"是",

cancelButtonText:"否"

}).then(function(result){

// console.log("-")

if(result.value == true){

//console.log("+")

$.ajax({

"url": "/management?method=delete&id=" + id,

"type":"get",

"dataType":"json",

"success":function(json){

//console.log("++");

if(json.result == "ok"){

window.location.reload();

} else{

Swal.fire({

title:json.result

})

}

}

})

}

})

}

</script>

</head>

<body>

<div class="container">

<fieldset>

<legend>油画列表</legend>

<div style="height: 40px">

<a href="/management?method=show_create" class="btn-button">新增</a>

</div>

<!-- 油画列表 -->

<table cellspacing="0px">

<thead>

<tr style="width: 150px;">

<th style="width: 100px">分类</th>

<th style="width: 150px;">名称</th>

<th style="width: 100px;">价格</th>

<th style="width: 400px">描述</th>

<th style="width: 100px">操作</th>

</tr>

</thead>

<c:forEach items="${pageModel.pageData }" var="painting" varStatus="idx">

<tr>

<td>

<c:choose>

<c:when test="${painting.category == 1}">现实主义</c:when>

<c:when test="${painting.category == 2}">抽象主义</c:when>

<c:otherwise>未知类型</c:otherwise>

</c:choose>

</td>

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

<td><fmt:formatNumber pattern="￥0.00" value="${painting.price }"></fmt:formatNumber></td>

<td>${painting.description }</td>

<td>

<a class="oplink" data-preview="${painting.preview }" data-pname="${painting.pname }" href="javascript:void(0)" onclick="showPreview(this)">预览</a>

<a class="oplink" href="/management?method=show_update&id=${painting.id }">修改</a>

<a class="oplink" data-id="${painting.id }" data-pname="${painting.pname }" data-preview="${painting.preview }" onclick="del(this)" href="javascript:void(0)">删除</a>

</td>

</tr>

</c:forEach>

</table>

<!-- 分页组件 -->

<ul class="page">

<li><a href="/management?method=list&p=1">首页</a></li>

<li><a href="/management?method=list&p=${pageModel.hasPreviousPage?pageModel.page - 1:1 }">上页</a></li>

<c:forEach begin="1" end="${pageModel.totalPages}" var="pno"  step="1">

<li class="${pno==pageModel.page?'active':''}"><a href="/management?method=list&p=${pno }">${pno }</a></li>

</c:forEach>

<li><a href="/management?method=list&p=${pageModel.hasNextPage?pageModel.page + 1:pageModel.totalPages}">下页</a></li>

<li><a href="/management?method=list&p=${pageModel.totalPages }">尾页</a></li>

</ul>

</fieldset>

</div>

</body>

</html>

//PaintingService

package com.imooc.mgallery.service;

/**

 * service完成完整的程序业务逻辑

 * @author zxy

 *

 */

import java.util.List;

import javax.management.RuntimeErrorException;

import com.imooc.mgallery.dao.PaintingDao;

import com.imooc.mgallery.entity.Painting;

import com.imooc.mgallery.utils.PageModel;

import com.imooc.mgallery.utils.XmlDataSource;

public class PaintingService {

private PaintingDao paintingDao = new PaintingDao();

public PageModel pagination(int page,int rows,String...category) {

if (rows == 0) {

throw new RuntimeException("无效的rows参数");

}

if (category.length == 0 || category[0] == null) {

return paintingDao.pagination(page, rows);

} else {

return paintingDao.pagination(Integer.parseInt(category[0]),page, rows);

}

}

/**

* 新增数据

* @param painting

*/

public void create(Painting painting) {

paintingDao.create(painting);

}

public Painting findById(Integer id) {

Painting p = paintingDao.findById(id);

if (p == null) {

throw new RuntimeException("[id = " + id + "]的油画不存在");

}

return p;

}

public void update(Painting newPainting,int isPreviewModified) {

Painting painting = paintingDao.findById(newPainting.getId());

painting.setCategory(newPainting.getCategory());

painting.setDescription(newPainting.getDescription());

painting.setPname(newPainting.getPname());

painting.setPrice(newPainting.getPrice());

if (isPreviewModified == 1) {//图片被更改了

painting.setPreview(newPainting.getPreview());

} 

paintingDao.update(painting);

}

public void delete(Integer id) {

paintingDao.delete(id);

}

public static void main(String[] args) {

PaintingService paintingService = new PaintingService();

PageModel pageModel = paintingService.pagination(2, 6);

// System.out.println(pageModel.getPageData());

List<Painting> paintingList = pageModel.getPageData();

for (Painting painting : paintingList) {

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

}

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

}

}

//PaintingDao

package com.imooc.mgallery.dao;

/**

 * 油画数据访问对象

 * 获取原始数据  对其进行分页处理

 * Dao负责与底层数据进行交互

 * @author zxy

 *

 */

import java.util.ArrayList;

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 {

/**

* 分页查询油画数据

* @param page 页号

* @param rows 每页记录数

* @return PageModel分页对象

*/

public PageModel pagination(int page,int rows) {

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

PageModel pageModel = new PageModel(list, page, rows);

return pageModel;

}

/**

* 按类分页查询

* @param category

* @param page

* @param rows

* @return

*/

public PageModel pagination(int category,int page,int rows) {

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

List<Painting> categoryList = new ArrayList<Painting>();

for (Painting painting : list) {

if (painting.getCategory() == category) {

categoryList.add(painting);

}

}

PageModel pageModel = new PageModel(categoryList, page, rows);

return pageModel;

}

/**

* 数据新增

*/

public void create(Painting painting) {

XmlDataSource.append(painting);

}

public Painting findById(Integer id) {

List<Painting> data = XmlDataSource.getRawData();

Painting p = null;

for (Painting painting : data) {

if (painting.getId() == id) {

p = painting;

break;

}

}

return p;

}

public void update(Painting painting) {

XmlDataSource.update(painting);

}

public void delete(Integer id) {

XmlDataSource.delete(id);

}

}

//XmlDataSource

package com.imooc.mgallery.utils;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.OutputStreamWriter;

import java.io.UnsupportedEncodingException;

import java.io.Writer;

import java.net.URLDecoder;

import java.util.ArrayList;

import java.util.List;

import org.dom4j.Document;

import org.dom4j.DocumentException;

import org.dom4j.Element;

import org.dom4j.Node;

import org.dom4j.io.SAXReader;

import com.imooc.mgallery.entity.Painting;

/**

 * 数据源类，用于将XML文件解析为Java对象

 * 

 * 

 * @author zxy

 *

 */

public class XmlDataSource {

//通过static关键字保证数据的全局唯一

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

private static String dataFile;

static {

//得到painting.xml文件完整物理路径

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

reload();

}

private static void reload() {

URLDecoder decoder = new URLDecoder();

try {

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

System.out.println(dataFile);

//利用Dom4j对XML进行解析

SAXReader reader = new SAXReader();

//获取document文档对象

Document document = reader.read(dataFile);

//Xpath得到XML节点集合

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

data.clear();

for (Node node : nodes) {

Element element = (Element)node;

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

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

// System.out.println(id + ":" + pname);

Painting painting = new Painting();

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

painting.setPname(pname);

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

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

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

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

data.add(painting);

}

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

/**

* 获取所有油画Painting 对象

* @return

*/

public static List<Painting> getRawData() {

return data;

}

public static void append(Painting painting) {

//1.读取XML文档，得到Document对象

SAXReader reader = new SAXReader();

Writer writer = null;//用于向文件写入字符流

try {

Document document = reader.read(dataFile);

//2.创建新的painting节点

Element root = document.getRootElement();//<root>

Element p = root.addElement("painting"); 

//3.创建painting节点的子节点

p.addAttribute("id", String.valueOf(data.size()));

p.addElement("pname").setText(painting.getPname());

p.addElement("category").setText(painting.getCategory().toString());

p.addElement("price").setText(painting.getPrice().toString());

p.addElement("preview").setText(painting.getPreview());

p.addElement("description").setText(painting.getDescription());

//4.写入XML

writer = new OutputStreamWriter(new FileOutputStream(dataFile),"utf-8");

document.write(writer);

System.out.println(dataFile);

} 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();

}

}

reload();//保证内存与文件的数据一致

}

}

/**

* 更新对应id的XML油画数据

* @param painting

*/

public static void update(Painting painting) {

SAXReader reader = new SAXReader();

Writer writer = null;

try {

Document document = reader.read(dataFile);

//节点路径[@属性名=属性值]

// /root/painting[@id=x]

List<Node> nodes =  document.selectNodes("/root/painting[@id =" + painting.getId() +"]");

if (nodes.size() == 0) {

throw new RuntimeException("id = " + painting.getId() + "编号油画不存在");

}

Element p = (Element)nodes.get(0);

p.selectSingleNode("pname").setText(painting.getPname());

p.selectSingleNode("category").setText(painting.getCategory().toString());

p.selectSingleNode("price").setText(painting.getPrice().toString());

p.selectSingleNode("preview").setText(painting.getPreview());

p.selectSingleNode("description").setText(painting.getDescription());

p.selectSingleNode("preview").setText(painting.getPreview());

writer = new OutputStreamWriter(new FileOutputStream(dataFile),"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();

}

}

reload();

}

}

public static void delete(Integer id) {

SAXReader reader = new SAXReader();

Writer writer = null;

try {

Document document = reader.read(dataFile);

List<Node> nodes = document.selectNodes("/root/painting[@id=" + id +"]");

if (nodes.size() == 0) {

throw new RuntimeException("id = " + id + "编号油画不存在");

}

Element p = (Element)nodes.get(0);

p.getParent().remove(p);

writer = new OutputStreamWriter(new FileOutputStream(dataFile),"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();

}

}

reload();

}

}

public static void main(String []args) {

Painting painting = new Painting();

painting.setPname("Jhon snow");

painting.setCategory(1);

painting.setPrice(5000);

painting.setPreview("/upload/Jhon snow.jpg");

painting.setDescription("snow");

XmlDataSource.append(painting);

}

}