Jsp+Servlet實現文件上傳下載文件上傳（一）

2024-09-05 00:23:33

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文件上傳和下載功能是Java Web必備技能，很實用。
本文使用的是Apache下的著名的文件上傳組件
org.apache.commons.fileupload 實現
下面結合最近看到的一些資料以及自己的嘗試，先寫第一篇文件上傳。后續會逐步實現下載，展示文件列表，上傳信息持久化等。

廢話少說，直接上代碼

第一步，引用jar包，設置上傳目錄

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

上傳目錄：WEB-INF/tempFiles和WEB-INF/uploadFiles

第二步，編寫JSP頁面

<%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <html> <head>  <title>文件上傳測試</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="上傳"> </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，編寫Servlet，處理文件上傳的核心

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;  /**  * 處理文件上傳  *  * @author xusucheng  * @create 2017-12-27  **/ @WebServlet("/UploadServlet") public class UploadServlet extends HttpServlet {  @Override  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {   //設置文件上傳基本路徑   String savePath = this.getServletContext().getRealPath("/WEB-INF/uploadFiles");   //設置臨時文件路徑   String tempPath = this.getServletContext().getRealPath("/WEB-INF/tempFiles");   File tempFile = new File(tempPath);   if (!tempFile.exists()) {    tempFile.mkdir();   }    //定義異常消息   String errorMessage = "";   //創建file items工廠   DiskFileItemFactory factory = new DiskFileItemFactory();   //設置緩沖區大小   factory.setSizeThreshold(1024 * 100);   //設置臨時文件路徑   factory.setRepository(tempFile);   //創建文件上傳處理器   ServletFileUpload upload = new ServletFileUpload(factory);   //監聽文件上傳進度   ProgressListener progressListener = new ProgressListener() {    public void update(long pBytesRead, long pContentLength, int pItems) {     System.out.println("正在讀取文件： " + pItems);     if (pContentLength == -1) {      System.out.println("已讀?。?" + pBytesRead + " 剩余0");     } else {      System.out.println("文件總大?。?quot; + pContentLength + " 已讀?。?quot; + pBytesRead);     }    }   };   upload.setProgressListener(progressListener);    //解決上傳文件名的中文亂碼   upload.setHeaderEncoding("UTF-8");   //判斷提交上來的數據是否是上傳表單的數據   if (!ServletFileUpload.isMultipartContent(request)) {    //按照傳統方式獲取數據    return;   }    //設置上傳單個文件的大小的最大值，目前是設置為1024*1024字節，也就是1MB   upload.setFileSizeMax(1024 * 1024);   //設置上傳文件總量的最大值，最大值=同時上傳的多個文件的大小的最大值的和，目前設置為10MB   upload.setSizeMax(1024 * 1024 * 10);    try {    //使用ServletFileUpload解析器解析上傳數據，解析結果返回的是一個List<FileItem>集合，每一個FileItem對應一個Form表單的輸入項    List<FileItem> items = upload.parseRequest(request);    Iterator<FileItem> iterator = items.iterator();    while (iterator.hasNext()) {     FileItem item = iterator.next();      //判斷jsp提交過來的是不是文件     if (item.isFormField()) {      errorMessage = "請提交文件！";      break;     } else {      //文件名      String fileName = item.getName();      if (fileName == null || fileName.trim() == "") {       System.out.println("文件名為空！");      }      //處理不同瀏覽器提交的文件名帶路徑問題      fileName = fileName.substring(fileName.lastIndexOf("//") + 1);      //文件擴展名      String fileExtension = fileName.substring(fileName.lastIndexOf(".") + 1);      //判斷擴展名是否合法      if (!validExtension(fileExtension)) {       errorMessage = "上傳文件非法！";       item.delete();       break;      }      //獲得文件輸入流      InputStream in = item.getInputStream();      //得到保存文件的名稱      String saveFileName = createFileName(fileName);      //得到文件保存路徑      String realFilePath = createRealFilePath(savePath, saveFileName);      //創建文件輸出流      FileOutputStream out = new FileOutputStream(realFilePath);      //創建緩沖區      byte buffer[] = new byte[1024];      int len = 0;      while ((len = in.read(buffer)) > 0) {       //寫文件       out.write(buffer, 0, len);      }      //關閉輸入流      in.close();      //關閉輸出流      out.close();      //刪除臨時文件 TODO      item.delete();      //將上傳文件信息保存到附件表中 TODO     }     }    } catch (FileUploadBase.FileSizeLimitExceededException e) {    e.printStackTrace();    request.setAttribute("errorMessage", "單個文件超出最大值?。?！");    request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response);    return;   } catch (FileUploadBase.SizeLimitExceededException e) {    e.printStackTrace();    request.setAttribute("errorMessage", "上傳文件的總的大小超出限制的最大值?。。?quot;);    request.getRequestDispatcher("pages/upload/upload.jsp").forward(request, response);    return;   } catch (FileUploadException e) {    e.printStackTrace();    request.setAttribute("errorMessage", "文件上傳失?。。?！");    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;  }   /**   * 根據基本路徑和文件名稱生成真實文件路徑，基本路徑//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，測試

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

Jsp,Servlet,文件上傳,文件下載