JavaWeb中上传和下载文件实例代码

一丶先引入上传下载的lib

二丶上传的的servlet

package com.test.action;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;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 org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.FileUploadException;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;@WebServlet("/upload")public class FileUpLoadAction extends HttpServlet {  private static final long serialVersionUID = 1L;  protected void doPost(HttpServletRequest request,      HttpServletResponse response) throws ServletException, IOException {    // 设置编码    request.setCharacterEncoding("utf-8");     //对提交的数据进行处理，保存上传文件     boolean success = processUpload(request);    if(success){      //获取表单text控件的值      String account = request.getAttribute("account").toString();      System.out.println(account);      //获取文件上传的原始名称      String fileName = request.getAttribute("upfile").toString();      System.out.println(fileName);      //获取文件上传后，服务器上保存的名字      String fileNameServer = request.getAttribute("upfileServer").toString();      System.out.println(fileNameServer);      request.setAttribute("upfile", fileNameServer);      request.setAttribute("message", "上传成功");    }    request.getRequestDispatcher("/upload.jsp").forward(request, response);  }  private boolean processUpload(HttpServletRequest request) {    boolean success = true;    String message = null;    // 获取文件需要上传到的路径    String path = request.getServletContext().getRealPath("/upload");    System.out.println(path);    // 如果此文件夹不存在，则构造此文件夹    File f = new File(path);    if (!f.exists()) {      f.mkdir();    }    // 构造出文件工厂，用于存放JSP页面中传递过来的文件    DiskFileItemFactory factory = new DiskFileItemFactory();    // 设置上传文件的保存路径    factory.setRepository(f);    // 设置缓存大小，如果文件大于缓存大小时，则先把文件放到缓存中    factory.setSizeThreshold(1 * 1024 * 1024);    ServletFileUpload upload = new ServletFileUpload(factory);    // 设置可以上传文件大小的上界20MB    upload.setSizeMax(20 * 1024 * 1024);    try {      // 可以上传多个文件      List<FileItem> list = (List<FileItem>) upload.parseRequest(request);      for (FileItem item : list) {        // 获取表单的属性名字        String name = item.getFieldName();        if (item.isFORMField()) {          String value = item.getString();          //解决乱码问题          value = new String(value.getBytes("iso-8859-1"),"utf-8");           request.setAttribute(name, value);        } else {          // 获得文件类型          String contentType = item.getContentType();          // 获得文件大小          long fileSize = item.getSize();          // 获取路径名          String value = item.getName();          // 索引到最后一个反斜杠          int start = value.lastIndexOf("\\");          // 截取 上传文件的 字符串名字，加1是 去掉反斜杠，          String filename = value.substring(start + 1);          if (filename != null && !filename.trim().equals("")) {            // 如果上传的文件不是图片，那么不上传            String allImgExt = ".jpg|.jpeg|.gif|.bmp|.png|";            String extName = filename.substring(filename.indexOf("."), filename.length());            if (allImgExt.indexOf(extName + "|") == -1) {              message = "该文件类型不允许上传。请上传 " + allImgExt                  + " 类型的文件，当前文件类型为" + extName;              success = false;              break;            }            request.setAttribute(name, filename);            // 随机数产生名称            String newName = System.currentTimeMillis() + extName;            request.setAttribute(name + "Server", newName);            // 将文件保存到服务器中            InputStream in = item.getInputStream();            // 原文件名            // OutputStream out = new FileOutputStream(new File(path, filename));            // 随机数文件名            OutputStream out = new FileOutputStream(new File(path,                newName));            int length = 0;            byte[] buf = new byte[1024];            while ((length = in.read(buf)) != -1) {              out.write(buf, 0, length);            }            in.close();            out.close();          }        }      }    } catch (FileUploadException e) {      message = "文件的内容过大，请上传小于20MB的文件" ;      success = false;      e.printStackTrace();    } catch (IOException e) {      success = false;      e.printStackTrace();    }    request.setAttribute("message", message);    return success;  }}