java eclipse 中檔案的上傳和下載示例解析
阿新 • • 發佈:2020-07-15
檔案的上傳與下載(一)
在實現檔案上傳和下載之前我們需要做一些準備工作,在Apache官網去下載檔案上傳下載的兩個元件,下載連結這裡給出:common-fileupload元件下載:http://commons.apache.org/proper/commons-fileupload/
common-io元件下載:http://commons.apache.org/proper/commons-io/
根據自己需求下載對應版本
一、建立工程
將所需要的兩個開發包匯入到工程專案中如圖:
二、程式碼編寫
1.前端頁面程式碼
1). 在WebRoot目錄下新建一個fileUpload.jsp頁面,用來上傳檔案
<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>My JSP 'fileUpload.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <!-- 檔案上傳表單的提交方式必須是“post” 編碼型別必須為:enctype="multipart/form-data" --> <form action="UploadServlet" method="post" enctype="multipart/form-data"> username: <input type="text" name="username" /><br> file: <input type="file" name="file"><br> file2: <input type="file" name="file2"><br> <input type="submit" value="上傳檔案"> </form> </body> </html>
2).新建一個fileUploadResult.jsp頁面用來顯示結果資訊
<%@ page language="java" import="java.util.*,java.io.*" pageEncoding="GB18030"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>My JSP 'fileUploadResult.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <%-- <% //獲取流物件 InputStream inputStream = request.getInputStream(); BufferedReader br = new BufferedReader(new InputStreamReader(inputStream)); String buffer = null; while((buffer = br.readLine()) != null){ out.print(buffer + "<br>"); } br.close(); inputStream.close(); %> --%> ${message}<br> EL-username : ${requestScope.username} <br> EL-file1 : ${requestScope.file }<br> EL-file2 : ${requestScope.file2}<br> </body> </html>
2. 編寫上傳檔案處理的Servlet程式碼
1) UploadServlet.java程式碼如下:
package com.Servlet; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.List; 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 { /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { //得到上傳檔案的儲存目錄,將上傳的檔案放在webRoot目錄下(但是一般為了安全放在WEB-INF目錄下,不允許外界直接訪問,保證上傳的安全) String path = this.getServletContext().getRealPath("/upload"); File file = new File(path); //判斷上傳檔案的儲存目錄是否存在 if(!file.exists() && !file.isDirectory()){ System.out.println(path + "目錄不存在,需要建立!"); //建立目錄 file.mkdir(); } //訊息提示 String message = ""; try{ //使用Apache檔案上傳元件處理檔案上傳步驟: //1.建立一個DiskFileItemFactory工廠 DiskFileItemFactory factory = new DiskFileItemFactory(); //2.建立一個檔案上傳解析器 ServletFileUpload upload = new ServletFileUpload(factory); //解決中文亂碼 upload.setHeaderEncoding("UTF-8"); //3.判斷提交的資料普通表單的資料還是帶檔案上傳的表單 if(!upload.isMultipartContent(request)){ //如果是表單資料普通表單,則按照傳統方式獲取資料 return ; } //4.使用ServletFileUpload解析器解析上傳資料,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> list = upload.parseRequest(request); for(FileItem item : list){ //如果fileItem中封裝的是普通輸入項的資料 if(item.isFormField()){ //獲取欄位名字 String name = item.getFieldName(); //解決普通輸入項中中文亂碼問題 String value = item.getString("UTF-8");//value = new String(value.getBytes("iso8859-1"),"UTF-8"); System.out.println(name + " = " + value); }else{ //如果表單中提交的是上傳檔案 //獲得上傳的檔名稱 String filename = item.getName(); System.out.println(filename); if(filename == null || filename.trim().equals(" ")){ continue; } //注意:不同的瀏覽器提交的檔名稱是不一樣的,有些瀏覽器提交的檔案會帶有路徑,如“D:\\project\WebRoot\hello.jsp”,有一些是單純的檔名:hello.jsp //去掉獲取到檔名中的路徑名,保留單純的檔名 filename = filename.substring(filename.lastIndexOf("\\") + 1); //獲取item中的上傳檔案的輸入流 InputStream in = item.getInputStream(); //建立一個檔案輸入流 FileOutputStream out = new FileOutputStream(path + "\\" + filename); //建立一個緩衝區 byte buffer[] = new byte[1024]; //判斷輸入流中的資料是否已經讀取完畢的標誌位 int len = 0; //迴圈將輸入流讀入到緩衝區當中,(len = in.read(buffer)>0)就表示in裡面還有資料存在 while((len = in.read(buffer)) > 0){ //使用FileOutputStream輸出流將緩衝區的資料寫入到指定的目錄(path+"\\"+filename)當中 out.write(buffer,len); } //關閉輸入流 in.close(); //關閉輸出流 out.close(); //刪除處理檔案上傳生成的臨時檔案 item.delete(); message = "檔案上傳成功!"; } } }catch(Exception e){ message = "檔案上傳失敗!"; e.printStackTrace(); } request.setAttribute(message,message); request.getRequestDispatcher("fileUploadResult.jsp").forward(request,response); } }
2)web.xml檔案中的配置
<?xml version="1.0" encoding="UTF-8"?> <web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <servlet> <servlet-name>UploadServlet</servlet-name> <servlet-class>com.Servlet.UploadServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>UploadServlet</servlet-name> <url-pattern>/UploadServlet</url-pattern> </servlet-mapping> </web-app>
結果:
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