在Java项目中使用fileupload组件如何实现一个文件上传功能

package pers.msidolphin.uploadservlet.web;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.UnsupportedEncodingException;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import java.util.List;import java.util.UUID;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 UploadServlet extends HttpServlet { private static final long serialVersionUID = 1L;  public UploadServlet() {  super(); }  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  //获取解析工厂  DiskFileItemFactory factory = new DiskFileItemFactory();  //得到解析器  ServletFileUpload parser = new ServletFileUpload(factory);  //解决文件名乱码问题  parser.setHeaderEncoding("UTF-8");  //判断上传表单类型  if(!ServletFileUpload.isMultipartContent(request)) {   return;  }  try {   //调用解析器解析上传数据   List<FileItem> fileItems = parser.parseRequest(request);   //获得保存上传文件目录的路径   String uploadPath = request.getServletContext().getRealPath("/WEB-INF/upload");   //遍历List集合   for (FileItem fileItem : fileItems) {    //判断是否为普通表单字段    if(fileItem.isFormField()) {     //如果是普通表单字段则打印到控制台     if(fileItem.getString() == null || "".equals(fileItem.getString().trim())) {      continue;     }     System.out.println(fileItem.getFieldName() + " = " + new String(fileItem.getString().getBytes("ISO-8859-1"), "UTF-8"));    }else {     //获得文件路径     String filePath = fileItem.getName();     //如果并未上传文件，继续处理下一个字段     if(filePath == null || "".equals(filePath.trim())) {      continue;     }     System.out.println("处理文件:" + filePath);     //截取文件名     String fileName = filePath.substring(filePath.lastIndexOf("\\") + 1);     String reallyName = this.createFileName(fileName);     String reallyPath = this.mkDir(reallyName, uploadPath);     //下面都是普通的IO操作了     InputStream in = fileItem.getInputStream();     FileOutputStream out = new FileOutputStream(reallyPath + "\\" + reallyName);     byte[] buffer = new byte[1024];     int len = 0;     while((len = in.read(buffer)) > 0) {      out.write(buffer, 0, len);     }     out.close();     in.close();    }   }   System.out.println("处理完毕...");  } catch (Exception e) {   // TODO Auto-generated catch block   e.printStackTrace();  } }  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  doGet(request, response); } //随机产生唯一的文件名 private String createFileName(String fileName) throws NoSuchAlgorithmException, UnsupportedEncodingException {  String extension = fileName.substring(fileName.lastIndexOf("."));  MessageDigest md = MessageDigest.getInstance("md5");  String currentTime = System.currentTimeMillis() + "";  return UUID.randomUUID() + currentTime + extension; } //根据哈希值产生目录 private String mkDir(String fileName, String uploadPath) {  int hasCode = fileName.hashCode();  //低四位作为一级目录  int parentDir = hasCode & 0xf;  //二级目录  int childDir = hasCode & 0xff >> 2;  File file = new File(uploadPath + "\\" + parentDir + "\\" + childDir);  if(!file.exists()) {   file.mkdirs();  }  uploadPath = uploadPath + "\\" + parentDir + "\\" + childDir;  return uploadPath; }}