在Javaweb中，上傳下載是經常用到的功能，對于文件上傳，瀏覽器在上傳的過程中是以流的過程將文件傳給服務器，一般都是使用commons-fileupload這個包實現上傳功能，因為commons-fileupload依賴于commons-io這個包，所以需要下載這兩個包commons-fileupload-1.2.1.jar和commons-io-1.3.2.jar。
1、搭建環境
創建Web項目，將包導入到項目lib下
2、實現文件上傳
(第一種上傳的方法)
新建upload.jsp頁面
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>upload file</title></head><body> <!--這里的<%=request.getContextPath()%>是表示項目的絕對路徑，也就是說不管你以后將項目拷貝到哪個位置，它都會找到準確的路徑 --> <form action="<%=request.getContextPath()%>/uploadServlet" enctype="multipart/form-data" method="post"> <span>選擇文件：</span><input type="file" name="file1"> <input type="submit" value="上傳"> </form></body></html>
新建處理文件上傳的Servlet
package com.load;import java.io.File;import java.io.IOException;import java.util.List;import javax.servlet.ServletContext;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("/uploadServlet")public class uploadServlet extends HttpServlet { private static final long serialVersionUID = 1L; public uploadServlet() { super(); } /* fileupload 包中， HTTP 請求中的復雜表單元素都被看做一個 FileItem 對象； * FileItem 對象必須由 ServletFileUpload 類中的 parseRequest() 方法解析 HTTP 請求 * （即被包裝之后的 HttpServletRequest 對象）出來，即分離出具體的文本表單和上傳文件 * */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //通過isMultipartContent()方法：分析請求里面是不是有文件上的請求， boolean isMultipart = ServletFileUpload.isMultipartContent(request); if(isMultipart){ //創建可設置的磁盤節點工廠 DiskFileItemFactory factory = new DiskFileItemFactory(); //獲取請求的上下文信息 ServletContext servletContext = request.getServletContext(); //緩存目錄，每個服務器特定的目錄 File repository = (File) servletContext.getAttribute("javax.servlet.context.tempdir"); //設置服務器的緩存目錄 factory.setRepository(repository); //ServletFileUpload 對象的創建需要依賴于 FileItemFactory //工廠將獲得的上傳文件 FileItem 對象保存至服務器硬盤，即 DiskFileItem 對象。 ServletFileUpload upload = new ServletFileUpload(factory); try { //解析即被包裝之后的 HttpServletRequest對象，既是分離文本表單和上傳文件（http請求會被包裝為HttpServletRequest） List<FileItem> items = upload.parseRequest(request); for(FileItem item:items){ String fieldName = item.getFieldName(); String fileName = item.getName(); String contentType = item.getContentType(); boolean isInMemory = item.isInMemory(); long sizeInBytes = item.getSize(); //實例化一個文件 //request.getRealPath(獲取真實路徑) File file = new File(request.getRealPath("/")+"/loads"+fileName.substring(fileName.lastIndexOf("http://")+1,fileName.length())); item.write(file); } } catch (FileUploadException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}(第二種上傳的方法)
新建Jsp頁面(同上，只是路徑改變下)
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>upload file</title></head><body> <!--這里的<%=request.getContextPath()%>是表示項目的絕對路徑，也就是說不管你以后將項目拷貝到哪個位置，它都會找到準確的路徑 --> <form action="<%=request.getContextPath()%>/uploadservlet1" enctype="multipart/form-data" method="post"> <span>選擇文件：</span><input type="file" name="file1"> <input type="submit" value="上傳"> </form></body></html>
建立Servlet處理上傳
package com.load;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import javax.servlet.ServletException;import javax.servlet.annotation.MultipartConfig;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.Part;@WebServlet("/uploadservlet1")@MultipartConfig(location="")public class uploadservlet1 extends HttpServlet { private static final long serialVersionUID = 1L; public uploadservlet1() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); request.setCharacterEncoding("utf-8"); //取得上傳文件，讀取文件 Part part = request.getPart("file1"); //定義一個變量去接收文件名 String filename = null; //Content-Disposition: 就是當用戶想把請求所得的內容存為一個文件的時候提供一個默認的文件名 //Content-Disposition：告訴瀏覽器以下載的方式打開文件 for (String content : part.getHeader("content-disposition").split(";")) { System.out.println(content); //取得文件名 if (content.trim().startsWith("filename")) { //截取文件名 filename = content.substring( content.indexOf('=') + 1).trim().replace("/"", ""); } } //輸出流 OutputStream out = null; //輸入流 InputStream filecontent = null; //File.separator 取得系統的分割線等數據 out = new FileOutputStream(new File("e:/loads" + File.separator + filename)); int read; //獲得一個輸入流 filecontent = part.getInputStream(); final byte[] bytes = new byte[1024]; while ((read = filecontent.read(bytes)) != -1) { out.write(bytes, 0, read); } System.out.println("New file " + filename + " created at " + "/loads"); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); }}(第三種上傳的方法)
這里使用的是jspSmartUpload包上傳下載，筆者認為這種上傳下載較為簡單，但是好像不是很多人用，不懂。
創建HTML頁面
<!DOCTYPE html><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>上傳文件</title></head><body> <p> </p> <p align="center">上傳文件選擇</p> <form method="post" Action="../DouploadServlet" enctype="multipart/form-data"> <table width="75%" border="1" align="center"> <tr><td><div align="center"> 1.<input type="file" name="file1" > </div></td></tr> <tr><td><div align="center"> 2.<input type="file" name="file2" > </div></td></tr> <tr><td><div align="center"> 3.<input type="file" name="file3" > </div></td></tr> <tr><td><div align="center"> <input type="submit" name="Submit" value="上傳他"> </div></td></tr> </table> </form></body></html>
創建Servlet處理上傳文件
package com.load;import java.io.IOException;import java.io.PrintWriter;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 javax.servlet.jsp.JspFactory;import javax.servlet.jsp.PageContext;import com.jspsmart.upload.File;import com.jspsmart.upload.SmartUpload;import com.jspsmart.upload.SmartUploadException;@WebServlet("/DouploadServlet")public class DouploadServlet extends HttpServlet { private static final long serialVersionUID = 1L; public DouploadServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); //新建一個智能上傳對象 SmartUpload su = new SmartUpload(); /* * PageContext pageContext; HttpSession session; ServletContext application; ServletConfig config; JspWriter out; Object page = this; HttpServletRequest request, HttpServletResponse response 其中page對象，request和response已經完成了實例化，而其它5個沒有實例化的對象通過下面的方式實例化 pageContext = jspxFactory.getPageContext(this, request, response,null, true, 8192, true); */ //通過Jsp工廠類獲取上下文環境 PageContext pagecontext = JspFactory.getDefaultFactory().getPageContext(this, request, response, null, true, 8192, true); //上傳初始化 su.initialize(pagecontext); //上傳文件 try { su.upload(); //將上傳文件保存到指定目錄 int count = su.save("/share"); out.println(count+"個文件上傳成功!<br>"+su.toString()); } catch (SmartUploadException e) { e.printStackTrace(); } //逐個提取上傳文件信息 for(int i=0;i<su.getFiles().getCount();i++){ File file = su.getFiles().getFile(i); //如果文件不存在 if(file.isMissing()) continue; //顯示當前文件信息 out.println("<table border=1>"); out.println("<tr><td>表單項名(FieldName)</td></td>"+file.getFieldName()+"</td></tr>"); out.println("<tr><td>文件長度</td><td>"+file.getSize()+"</td></tr>"); out.println("<tr><td>文件名</td><td>"+file.getFileName()+"</td></tr>"); out.println("<tr><td>文件擴展名</td><td>"+file.getFileExt()+"</td></tr>"); out.println("<tr><td>文件全名</td><td>"+file.getFilePathName()+"</td></tr>"); out.println("</table><br>"); } } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); }}注意：代碼 int count = su.save("/share");表示你需要先建個文件夾，所以你可以先在Webcontent建立一個，然后將項目取消部署，再重新部署進去之后就會在運行那邊建立起一個文件夾了！
或者你可以直接找到運行的路徑，然后建立share文件夾。
3、實現文件下載
(第一種文件下載)
注意：該代碼是直接訪問Servlet類的
package com.load;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;//直接使用Http://localhost:8080/Test1/download進行下載，但是這個有缺陷，如果下載文件名中有中文，就會變成亂碼現象！@WebServlet("/download")public class download extends HttpServlet { private static final long serialVersionUID = 1L; public download() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/plain;charset=utf-8"); response.setCharacterEncoding("utf-8"); response.setHeader("Location","中文.txt"); response.setHeader("Content-Disposition", "attachment; filename=" + "賬號.txt"); OutputStream outputStream = response.getOutputStream(); InputStream inputStream = new FileInputStream("E:/loads"+"/賬號.txt"); byte[] buffer = new byte[1024]; int i = -1; while ((i = inputStream.read(buffer)) != -1) { outputStream.write(buffer, 0, i); } outputStream.flush(); outputStream.close(); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}(第二種下載方法)
新建jsp頁面選擇下載
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>下載</title></head><body> <a href="../DoDownloadServlet?filename=呵呵.txt">點擊下載</a></body></html>
創建Servlet類進行下載（注意：該下載如果文件名是中文的話，一樣會出現亂碼現象）
package com.load;import java.io.BufferedInputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.URLEncoder;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 javax.servlet.jsp.JspFactory;import javax.servlet.jsp.PageContext;import org.hsqldb.lib.StringUtil;import com.jspsmart.upload.SmartUpload;import com.jspsmart.upload.SmartUploadException;@WebServlet("/DoDownloadServlet")public class DoDownloadServlet extends HttpServlet { private static final long serialVersionUID = 1L; public DoDownloadServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //得到下載文件的名稱 //String filename = request.getParameter("filename"); //String filename = new String(FileName.getBytes("iso8859-1"),"UTF-8"); //新建SmartUpload對象 SmartUpload su = new SmartUpload(); PageContext pagecontext = JspFactory.getDefaultFactory().getPageContext(this, request, response, null, true, 8192, true); //上傳初始化 su.initialize(pagecontext); //設置禁止打開該文件 su.setContentDisposition(null); //下載文件 try { su.downloadFile("/listener/"+filename); } catch (SmartUploadException e) { // TODO Auto-generated catch block e.printStackTrace(); } } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}(第三種下載的方法)
同上的jsp頁面代碼，這里就不再重復了。
新建Serlvet類，實現下載功能（注意：這里文件名就算是中文名，也不會出現亂碼問題了！）
package com.load;import java.io.BufferedInputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.URLEncoder;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 javax.servlet.jsp.JspFactory;import javax.servlet.jsp.PageContext;import org.hsqldb.lib.StringUtil;import com.jspsmart.upload.SmartUpload;import com.jspsmart.upload.SmartUploadException;@WebServlet("/DoDownloadServlet")public class DoDownloadServlet extends HttpServlet { private static final long serialVersionUID = 1L; public DoDownloadServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //獲得文件名稱 String path1 = request.getParameter("filename"); //獲得路徑名稱 String path = request.getSession().getServletContext().getRealPath("/listener/"+path1); // path是根據日志路徑和文件名拼接出來的 File file = new File(path); String filename = file.getName(); try { //判斷是否是IE11 Boolean flag= request.getHeader("User-Agent").indexOf("like Gecko")>0; //IE11 User-Agent字符串:Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko //IE6~IE10版本的User-Agent字符串:Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.0; Trident/6.0) if (request.getHeader("User-Agent").toLowerCase().indexOf("msie") >0||flag){ filename = URLEncoder.encode(filename, "UTF-8");//IE瀏覽器 }else { //先去掉文件名稱中的空格,然后轉換編碼格式為utf-8,保證不出現亂碼, //這個文件名稱用于瀏覽器的下載框中自動顯示的文件名 filename = new String(filename.replaceAll(" ", "").getBytes("UTF-8"), "ISO8859-1"); //firefox瀏覽器 //firefox瀏覽器User-Agent字符串: //Mozilla/5.0 (Windows NT 6.1; WOW64; rv:36.0) Gecko/20100101 Firefox/36.0 } InputStream fis = new BufferedInputStream(new FileInputStream(path)); byte[] buffer; buffer = new byte[fis.available()]; fis.read(buffer); fis.close(); response.reset(); response.addHeader("Content-Disposition", "attachment;filename=" +filename); response.addHeader("Content-Length", "" + file.length()); OutputStream os = response.getOutputStream(); response.setContentType("application/octet-stream"); os.write(buffer);// 輸出文件 os.flush(); os.close(); } catch (IOException e) { e.printStackTrace(); } System.out.println(filename); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。
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