这里需要用到插件ajaxfileupload.js，jar包：commons-fileupload-1.3.2.jar，commons-io-2.5.jar
注意红色部分的字！！！！
1、创建一个web工程，在配置web.xml
<!-- 文件上传的servlet -->
<servlet>
<servlet-name>UploadServlet</servlet-name>
<servlet-class>com.eviac.blog.restws.FileUpload</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>UploadServlet</servlet-name>
<url-pattern>/uploadFile</url-pattern>
</servlet-mapping>
2、upload.jsp页面
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>文件上传实例——servlet 异步上传文件（ajaxFileupload）</title> </head> <script type="text/javascript" src="js/jquery.js"></script> <script type="text/javascript" src="js/ajaxfileupload.js"></script> <script type="text/javascript"> function ajaxFileUpload() { $.ajaxFileUpload ( { url:'/servleToRestful/uploadFile',//用于文件上传的服务器端请求地址 secureuri:false,//一般设置为false fileElementId:'file',//文件上传空间的id属性 <input type="file" id="file" name="file" /> dataType: 'text',//返回值类型 一般设置为json success: function (data, status) //服务器成功响应处理函数 { //方法一，用后台返回值 alert(data);//后台out输出的值 //用ajaxFileUpload来判断成功与否，设置值 $('#myspan').html("上传成功！"); }, error: function (data, status, e)//服务器响应失败处理函数 { //方法一，用后台返回值 alert(data);//后台out输出的值 //用ajaxFileUpload来判断成功与否，设置值 $('#myspan').html("上传失败！"); } } ) return false; } </script> <body> <h1>文件上传实例——servlet 异步上传文件（ajaxFileupload）</h1> <!-- <form method="post" action="/servleToRestful/uploadFile" enctype="multipart/form-data"> 选择一个文件: <input type="file" name="uploadFile" /> <br/><br/> <input type="submit" value="上传" /> </form> --> <br/> <input type="file" id="file" name="file" /> <br /> <input type="button" value="上传" onclick="return ajaxFileUpload();"> <br> <p><span id="myspan"></span></p> </body> </html>
3、后台代码FileUpload类
package com.eviac.blog.restws; import java.io.File; import java.io.IOException; import java.io.PrintWriter; import java.util.List; import javax.servlet.ServletException; 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.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.ServletFileUpload; public class FileUpload extends HttpServlet{ private static final long serialVersionUID = 1L; // 上传文件存储目录 private static final String UPLOAD_DIRECTORY = "upload"; // 上传配置 private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3; // 3MB private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50; // 50MB public FileUpload(){ super(); } public void service(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException{ PrintWriter writer = response.getWriter(); // 检测是否为多媒体上传 if (!ServletFileUpload.isMultipartContent(request)) { // 如果不是则停止 writer.println("Error: 表单必须包含 enctype=multipart/form-data..."); writer.flush(); return; } //记住要写这句话，上传的文件名才不会乱码！！！！！！！！！ request.setCharacterEncoding("utf-8"); response.setContentType("text/html;charset=utf-8"); // 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); // 构造临时路径来存储上传的文件 // 这个路径相对当前应用的目录 String uploadPath = request.getContextPath() + File.separator + UPLOAD_DIRECTORY; //获取项目发布路径 下的upload文件夹 uploadPath = request.getSession().getServletContext().getRealPath("/upload"); // 如果目录不存在则创建 File uploadDir = new File(uploadPath); if (!uploadDir.exists()) { uploadDir.mkdir(); } 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()) { //这里处理文件中文乱码没用。。。。。。。。。 System.out.println(new String(item.getName().getBytes("utf-8"),"iso-8859-1")); String fileName = new File(item.getName()).getName(); String filePath = uploadPath + File.separator + fileName; File storeFile = new File(filePath); // 在控制台输出文件的上传路径 System.out.println(filePath); // 保存文件到硬盘 item.write(storeFile); //注意编码，不然返回前端会乱码！！！ writer.println(new String("上传成功！".getBytes("utf-8"),"iso-8859-1")); } } } } catch (Exception ex) { ex.printStackTrace(); } // 跳转到 message.jsp,这里使用了异步上传，所以不用跳转页面 //request.getRequestDispatcher("/message.jsp").forward(request, response); } }