Jsp+Servlet实现文件上传下载文件上传（一）

2020-07-26 23:16:06

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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