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1.建普通maven项目，或者maven项目，这里以普通maven为例，区别的jar包的导入方式啦
到中央仓库下载哦
2.结构
3.写fileservlet
public class FileServlet extends HttpServlet {@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//判断上传的文件是普通的表单还是带文件的表单（以表单方式提交）if(!ServletFileUpload.isMultipartContent(req)){return;//普通表单，终止方法运行}//创建文件上传后的保存路径String uploadPath=this.getServletContext().getRealPath("/WEB-INF/upload");File uploadFile=new File(uploadPath);if(!uploadFile.exists()){uploadFile.mkdir();//不存在，就创建这个目录}//缓存，临时文件放置String tmpPath=this.getServletContext().getRealPath("/WEB-INF/tmp");File file=new File(tmpPath);if(!file.exists()){file.mkdir();//不存在，就创建这个目录（临时）}//处理上传的文件，一般通过流获取try{//创建DiskFileItemFactory对象，处理文件上传限制 大小 路径DiskFileItemFactory factory=getDiskFileItemFactory(file);//获取ServletFileUploadServletFileUpload upload=getServletFileUpload(factory);//处理上传的文件String msg=uploadParseRequest(upload,req,uploadPath);//servlet请求转发req.setAttribute("msg",msg);req.getRequestDispatcher("info.jsp").forward(req,resp);} catch (Exception e) {e.printStackTrace();}}private static String uploadParseRequest(ServletFileUpload upload, HttpServletRequest req, String uploadPath) throws FileUploadException, IOException {String msg="";List<FileItem>fileItems=upload.parseRequest(req);for(FileItem fileItem:fileItems){if(fileItem.isFormField()){String name=fileItem.getFieldName();String value=fileItem.getString("UTF-8");System.out.println(name+":"+value);}else {String uploadFileName=fileItem.getName();System.out.println("文件："+uploadFileName);if(uploadFileName.trim().equals("")||uploadFileName==null){continue;}//获取文件名（/），和后缀名（.) /img.pngString fileName=uploadFileName.substring(uploadFileName.lastIndexOf("/")+1);String fileExtName=uploadFileName.substring(uploadFileName.lastIndexOf(".")+1);System.out.println("文件消息："+fileName+"类型"+fileExtName);//UUID 保证文件名唯一//UUID.randomUUID()随机生成一个通用码String uuidPath= UUID.randomUUID().toString();String realPath=uploadPath+"/"+uuidPath;File realPathFile=new File(realPath);if(!realPathFile.exists()){realPathFile.mkdir();}//获取上传文件的流InputStream inputStream=fileItem.getInputStream();FileOutputStream fos=new FileOutputStream(realPath+"/"+fileName);//缓冲区byte[]buffer=new byte[1024*1024];//判断读取完成？int len=0;while ((len=inputStream.read(buffer))>0){fos.write(buffer,0,len);}fos.close();inputStream.close();msg="success";fileItem.delete();}}return msg;}private static ServletFileUpload getServletFileUpload(DiskFileItemFactory factory) {ServletFileUpload upload=new ServletFileUpload(factory);//监听文件上传速度upload.setProgressListener(new ProgressListener() {@Overridepublic void update(long l, long l1, int i) {System.out.println("总大小："+l1+"已上传"+l);}});upload.setHeaderEncoding("UTF-8");upload.setFileSizeMax(1024*1024*10);//1024=1kb*1024=10Mreturn upload;}private static DiskFileItemFactory getDiskFileItemFactory(File file) {DiskFileItemFactory factory=new DiskFileItemFactory();//设置缓冲区，文件大于缓冲区放到临时文件factory.setSizeThreshold(1024*1024);factory.setRepository(file);return factory;}@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {}
}
4.index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/upload.do" enctype="multipart/form-data" method="post">上传用户：<input type="text" name="username"><br><p><input type="file" name="file1"></p><p><input type="file" name="file1"></p><p><input type="submit">||<input type="reset"></p>
</form>
</body>
</html>
5.info
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<%--上传文件大小有限制：get--%>
${msg}
</body>
</html>