ajax 提交所有表单内容及上传图片（文件），以及单独上传某个图片（文件）

我以演示上传图片为例子：

java代码如下（前端童鞋可以直接跳过看下面的html及js）：

package com.vatuu.web.action;

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

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 net.sf.json.JSONObject;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**
 * Servlet implementation class NewsUploadImage
 * 上传新闻配图
 */
@WebServlet("/NewsUploadImage")
public class NewsUploadImage extends HttpServlet {
    private static final long serialVersionUID = 1L;

    //上传配置
    private static final int MEMORY_THRESHOLD   = 1024 * 1024 ;  // 1MB
    private static final int MAX_FILE_SIZE      = 1024* 200 ; // 200k
    private static final int MAX_REQUEST_SIZE   = 1024 * 1024 ; // 1MB
    /**
     * @see HttpServlet#HttpServlet()
     */
    public NewsUploadImage() {
        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
        doPost(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        // 检测是否为多媒体上传
        if (!ServletFileUpload.isMultipartContent(request)) {
            // 如果不是则停止
            PrintWriter writer = response.getWriter();
            writer.println("Error: 表单必须包含 enctype=multipart/form-data");
            writer.flush();
            return;
        }

        // 配置上传参数
        DiskFileItemFactory factory = new DiskFileItemFactory();
        // 设置内存临界值 - 超过后将产生临时文件并存储于临时目录中
        factory.setSizeThreshold(MEMORY_THRESHOLD);
        // 设置临时存储目录
        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));

        ServletFileUpload upload = new ServletFileUpload(factory);

        // 设置最大文件上传值
        upload.setFileSizeMax(MAX_FILE_SIZE);

        // 设置最大请求值 (包含文件和表单数据)
        upload.setSizeMax(MAX_REQUEST_SIZE);

        // 中文处理
        upload.setHeaderEncoding("UTF-8"); 

        // 这个路径相对当前应用的目录
        String uploadPath = request.getServletContext().getRealPath("/download/news/images");

        // 如果目录不存在则创建
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }

        PrintWriter pw = response.getWriter();
        JSONObject jsonObject = new JSONObject();
        try {
            // 解析请求的内容提取文件数据
            @SuppressWarnings("unchecked")
            List<FileItem> formItems = upload.parseRequest(request);

            if (formItems != null && formItems.size() > 0) {
                // 迭代表单数据
                for (FileItem item : formItems) {
                    // 处理不在表单中的字段
                    if (!item.isFormField()) {
                        String fileName = new File(item.getName()).getName();
                        //获取文件后缀名
                        String prefix=fileName.substring(fileName.lastIndexOf(".")+1);
                        //判断文件类型
                        if(prefix.equals("jpg") || prefix.equals("gif") || prefix.equals("png") || prefix.equals("jpeg")){
                             //以时间戳+pt两字命名文件
                             long currentTime=System.currentTimeMillis();
                             String filePath = uploadPath  + currentTime+"pt."+prefix;
                             File storeFile = new File(filePath);
                             // 在控制台输出文件的上传路径
                             // 保存文件到硬盘
                             item.write(storeFile);
                             request.setAttribute("message",
                                 "文件上传成功!");
                             jsonObject.put("fileName", currentTime+"pt."+prefix);
                             jsonObject.put("url", filePath);

                             System.out.println("配图上传成功：" + filePath);
                        }else{
                            request.setAttribute("message",
                                    "不支持该文件类型!");
                            jsonObject.put("url", "");
                            System.out.println("配图上传失败,不支持该文件类型!");
                        }
                    }
                }
            }
        } catch (Exception ex) {
            request.setAttribute("message",
                    "错误信息: " + ex.getMessage());
            jsonObject.put("url", "");
        }

        pw.print(jsonObject.toString());
        pw.flush();
        pw.close();

    }

}

一次提交所有表单的HTML如下,表单必须添加enctype属性，才能提交文件：

<form action="${basePath}vatuu/NewsAction?setAction=Add" method="post" name="newsForm" id="newsForm" enctype="multipart/form-data">
                                  <table class="table_border table-form table-td-left table-th-normal">
                                      <tr>
                                          <th style="min-width: 150px; width: 20%">新闻标题</th>
                                          <td><input type="text" id="newsTitle" name="newsTitle" class="input" style="width:40%"></td>
                                      </tr>

                                      <tr  id="newsContent1">
                                          <th style="width: 20%">新闻内容</th>
                                          <td style="width: 80%;"  id="newsContent" name="newsContent"><script id="container" name="newsContent" type="text/plain" style="height: 700px; width: 99%;"></script></td>
                                      </tr>
                                      <tr id="newsUrl1" style="display: none">
                                          <th>链接地址</th>
                                          <td><input type="text" style="width: 40%;" id="newsUrl" name="newsUrl" value="http://" class="input" /></td>
                                      </tr>
                                      <tr>
                                          <th style="width: 20%">新闻配图</th>
                                          <td>
                                              <input type="hidden" id="newsImgUrl" name="newsImgUrl" value="">
                                              <input type="file" class="input" name="newsImage" id="newsImage"/>
                                              <a href="javascript:uploadNewsImg()" class="btn btn-blue"  >上传配图</a>
                                              <img id="showUploadImg"  width="80" height="50" style="display: none;" />
                                              <span  class="c-red" id="message" name="message"></span>
                                              <span>提示：文件大小不超过200k，建议图片宽高为245px*160px</span>
                                          </td>
                                      </tr>
                                      <tr>
                                          <td colspan="2" style="text-align: center;">
                                              <input  type="submit" class="btn btn-blue" value="发布新闻 "/>
                                              <input type="reset" class="btn btn-red" value="取消发布" >
                                          </td>
                                      </tr>
                                  </table>
                              </form>

这里的提交可以直接summit 提交整个表单。

但是也有的时候需要单独上传图片或文件，回显是否上传成功，这里就需要用ajax进行处理。

首先引入jquery。

html跟上个差不多，唯一不同的是，不能给form 添加enctype=“multipart/form-data”属性，因为这里单独上传的时候没问题，但是提交整个表单的时候，若加上这个属性，

则整体提交表单的时候又会上传之前的文件，会出错，因此此处去掉enctype属性。

html如下：

<form action="${basePath}vatuu/NewsAction?setAction=Add" method="post" name="newsForm" id="newsForm" >
                                  <table class="table_border table-form table-td-left table-th-normal">
                                      <tr>
                                          <th style="min-width: 150px; width: 20%">新闻标题</th>
                                          <td><input type="text" id="newsTitle" name="newsTitle" class="input" style="width:40%"></td>
                                      </tr>

                                      <tr  id="newsContent1">
                                          <th style="width: 20%">新闻内容</th>
                                          <td style="width: 80%;"  id="newsContent" name="newsContent"><script id="container" name="newsContent" type="text/plain" style="height: 700px; width: 99%;"></script></td>
                                      </tr>
                                      <tr id="newsUrl1" style="display: none">
                                          <th>链接地址</th>
                                          <td><input type="text" style="width: 40%;" id="newsUrl" name="newsUrl" value="http://" class="input" /></td>
                                      </tr>
                                      <tr>
                                          <th style="width: 20%">新闻配图</th>
                                          <td>
                                              <input type="hidden" id="newsImgUrl" name="newsImgUrl" value="">
                                              <input type="file" class="input" name="newsImage" id="newsImage"/>
                                              <a href="javascript:uploadNewsImg()" class="btn btn-blue"  >上传配图</a>
                                              <img id="showUploadImg"  width="80" height="50" style="display: none;" />
                                              <span  class="c-red" id="message" name="message"></span>
                                              <span>提示：文件大小不超过200k，建议图片宽高为245px*160px</span>
                                          </td>
                                      </tr>
                                      <tr>
                                          <td colspan="2" style="text-align: center;">
                                              <input  type="submit" class="btn btn-blue" value="发布新闻 "/>
                                              <input type="reset" class="btn btn-red" value="取消发布" >
                                          </td>
                                      </tr>
                                  </table>
                              </form>

对应的ajax异步请求如下，需要使用jquery中的FormData提交文件（好像jquery必须高于1.2版本）。newsImage则是input type=“file”的id，此处我是上传的图片

//上传新闻配图
            function uploadNewsImg(){
                var formData = new FormData($( "#newsForm" )[0]);
                formData.append("file",$("#newsImage")[0]);
                formData.append("name",name);
                $.ajax({
                    url:"../vatuu/NewsUploadImage",
                    type:"POST",
                    dataType:"json",
                    data:formData,
                    contentType: false,
                    processData: false,
                    success:function(data) {
                        if(data.url !="" && data.url != null){
                            $("#newsImgUrl").val(data.url);
                            var url = data.url;
                            //将上传的文件回显
                            $("#showUploadImg").css("display","block");
                            $("#showUploadImg").attr("src","../download/news/images/"+data.fileName);
                            $("#message").text("上传成功!");
                        }else{
                            $("#message").text("上传失败!请仔细检查您的图片类型和大小");
                        }
                    }
                });

            }

将返回的url 设置给之前隐藏的img标签，并把img 标签display: block ,这样就能判断图片是否成功了，最后再sumbit 整个表单就行了，

就可以返回的图片的url 提交给后台了。