Jsp+Servlet实现文件上传下载文件上传（一）

dinux

2018-01-01

文件上传和下载功能是Java Web必备技能，很实用。
本文使用的是Apache下的著名的文件上传组件
org.apache.commons.fileupload 实现
下面结合最近看到的一些资料以及自己的尝试，先写第一篇文件上传。后续会逐步实现下载，展示文件列表，上传信息持久化等。

废话少说，直接上代码

第一步，引用jar包，设置上传目录

commons-fileupload-1.3.1.jar
commons-io-2.4.jar

上传目录：WEB-INF/tempFiles和WEB-INF/uploadFiles

第二步，编写JSP页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %> 
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> 
<html> 
<head> 
 <title>文件上传测试</title> 
</head> 
<body> 
<form method="POST" enctype="multipart/form-data" action="<%=request.getContextPath()%>/UploadServlet"> 
 文件: <input type="file" name="upfile"><br/> 
 <br/> 
 <input type="submit" value="上传"> 
</form> 
<c:if test="${not empty errorMessage}"> 
 <input type="text" id="errorMessage" value="${errorMessage}" style="color:red;" disabled="disabled"> 
</c:if> 
</body> 
</html>

第三步，编写Servlet，处理文件上传的核心

package servlet; 
 
import org.apache.commons.fileupload.FileItem; 
import org.apache.commons.fileupload.FileUploadBase; 
import org.apache.commons.fileupload.FileUploadException; 
import org.apache.commons.fileupload.ProgressListener; 
import org.apache.commons.fileupload.disk.DiskFileItemFactory; 
import org.apache.commons.fileupload.servlet.ServletFileUpload; 
 
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 java.io.File; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.util.Calendar; 
import java.util.Iterator; 
import java.util.List; 
import java.util.UUID; 
 
/** 
 * 处理文件上传 
 * 
 * @author xusucheng 
 * @create 2017-12-27 
 **/ 
@WebServlet("/UploadServlet") 
public class UploadServlet extends HttpServlet { 
 @Override 
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
  //设置文件上传基本路径 
  String savePath = this.getServletContext().getRealPath("/WEB-INF/uploadFiles"); 
  //设置临时文件路径 
  String tempPath = this.getServletContext().getRealPath("/WEB-INF/tempFiles"); 
  File tempFile = new File(tempPath); 
  if (!tempFile.exists()) { 
   tempFile.mkdir(); 
  } 
 
  //定义异常消息 
  String errorMessage = ""; 
  //创建file items工厂 
  DiskFileItemFactory factory = new DiskFileItemFactory(); 
  //设置缓冲区大小 
  factory.setSizeThreshold(1024 * 100); 
  //设置临时文件路径 
  factory.setRepository(tempFile); 
  //创建文件上传处理器 
  ServletFileUpload upload = new ServletFileUpload(factory); 
  //监听文件上传进度 
  ProgressListener progressListener = new ProgressListener() { 
   public void update(long pBytesRead, long pContentLength, int pItems) { 
    System.out.println("正在读取文件： " + pItems); 
    if (pContentLength == -1) { 
     System.out.println("已读取： " + pBytesRead + " 剩余0"); 
    } else { 
     System.out.println("文件总大小：" + pContentLength + " 已读取：" + pBytesRead); 
    } 
   } 
  }; 
  upload.setProgressListener(progressListener); 
 
  //解决上传文件名的中文乱码 
  upload.setHeaderEncoding("UTF-8"); 
  //判断提交上来的数据是否是上传表单的数据 
  if (!ServletFileUpload.isMultipartContent(request)) { 
   //按照传统方式获取数据 
   return; 
  } 
 
  //设置上传单个文件的大小的最大值，目前是设置为1024*1024字节，也就是1MB 
  upload.setFileSizeMax(1024 * 1024); 
  //设置上传文件总量的最大值，最大值=同时上传的多个文件的大小的最大值的和，目前设置为10MB 
  upload.setSizeMax(1024 * 1024 * 10); 
 
  try { 
   //使用ServletFileUpload解析器解析上传数据，解析结果返回的是一个List<FileItem>集合，每一个FileItem对应一个Form表单的输入项 
   List<FileItem> items = upload.parseRequest(request); 
   Iterator<FileItem> iterator = items.iterator(); 
   while (iterator.hasNext()) { 
    FileItem item = iterator.next(); 
 
    //判断jsp提交过来的是不是文件 
    if (item.isFormField()) { 
     errorMessage = "请提交文件！"; 
     break; 
    } else { 
     //文件名 
     String fileName = item.getName(); 
     if (fileName == null || fileName.trim() == "") { 
      System.out.println("文件名为空！"); 
     } 
     //处理不同浏览器提交的文件名带路径问题 
     fileName = fileName.substring(fileName.lastIndexOf("\\") + 1); 
     //文件扩展名 
     String fileExtension = fileName.substring(fileName.lastIndexOf(".") + 1); 
     //判断扩展名是否合法 
     if (!validExtension(fileExtension)) { 
      errorMessage = "上传文件非法！"; 
      item.delete(); 
      break; 
     } 
     //获得文件输入流 
     InputStream in = item.getInputStream(); 
     //得到保存文件的名称 
     String saveFileName = createFileName(fileName); 
     //得到文件保存路径 
     String realFilePath = createRealFilePath(savePath, saveFileName); 
     //创建文件输出流 
     FileOutputStream out = new FileOutputStream(realFilePath); 
     //创建缓冲区 
     byte buffer[] = new byte[1024]; 
     int len = 0; 
     while ((len = in.read(buffer)) > 0) { 
      //写文件 
      out.write(buffer, 0, len); 
     } 
     //关闭输入流 
     in.close(); 
     //关闭输出流 
     out.close(); 
     //删除临时文件 TODO 
     item.delete(); 
     //将上传文件信息保存到附件表中 TODO 
    } 
 
   } 
 
  } catch (FileUploadBase.FileSizeLimitExceededException e) { 
   e.printStackTrace(); 
   request.setAttribute("errorMessage", "单个文件超出最大值！！！"); 
   request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response); 
   return; 
  } catch (FileUploadBase.SizeLimitExceededException e) { 
   e.printStackTrace(); 
   request.setAttribute("errorMessage", "上传文件的总的大小超出限制的最大值！！！"); 
   request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response); 
   return; 
  } catch (FileUploadException e) { 
   e.printStackTrace(); 
   request.setAttribute("errorMessage", "文件上传失败！！！"); 
   request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response); 
   return; 
  } 
 
  request.setAttribute("errorMessage", errorMessage); 
  request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response); 
 
 
 } 
 
 @Override 
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
  doGet(request, response); 
 } 
 
 private boolean validExtension(String fileExtension) { 
  String[] exts = {"jpg", "txt", "doc", "pdf"}; 
  for (int i = 0; i < exts.length; i++) { 
   if (fileExtension.equals(exts[i])) { 
    return true; 
   } 
 
  } 
 
  return false; 
 } 
 
 private String createFileName(String fileName) { 
  return UUID.randomUUID().toString() + "_" + fileName; 
 } 
 
 /** 
  * 根据基本路径和文件名称生成真实文件路径，基本路径\\年\\月\\fileName 
  * 
  * @param basePath 
  * @param fileName 
  * @return 
  */ 
 private String createRealFilePath(String basePath, String fileName) { 
  Calendar today = Calendar.getInstance(); 
  String year = String.valueOf(today.get(Calendar.YEAR)); 
  String month = String.valueOf(today.get(Calendar.MONTH) + 1); 
 
 
  String upPath = basePath + File.separator + year + File.separator + month + File.separator; 
  File uploadFolder = new File(upPath); 
  if (!uploadFolder.exists()) { 
   uploadFolder.mkdirs(); 
  } 
 
  String realFilePath = upPath + fileName; 
 
  return realFilePath; 
 } 
}

第四步，测试

http://localhost:8080/helloweb/pages/upload/upload.jsp

Jsp+Servlet实现文件上传下载文件上传（一）