JavaWeb文件上傳下載功效示例解析。本站提示廣大學習愛好者：（JavaWeb文件上傳下載功效示例解析）文章只能為提供參考，不一定能成為您想要的結果。以下是JavaWeb文件上傳下載功效示例解析正文
在Web運用體系開辟中，文件上傳和下載功效長短經常用的功效，明天來說一下JavaWeb中的文件上傳和下載功效的完成。
1. 上傳簡略示例
Jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>文件上傳下載</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/UploadServlet" enctype="multipart/form-data" method="post">
上傳用戶：<input type="text" name="username" /> <br />
上傳文件1：<input type="file" name="file1" /> <br />
上傳文件2：<input type="file" name="file2" /> <br />
<input type="submit" value="上傳 "/>
</form>
<br />
${requestScope.message}
</body>
</html>
Servlet
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try{
//1.獲得解析器工場
DiskFileItemFactory factory = new DiskFileItemFactory();
//2.獲得解析器
ServletFileUpload upload = new ServletFileUpload(factory);
//3.斷定上傳表單的類型
if(!upload.isMultipartContent(request)){
//上傳表單為通俗表單，則依照傳統方法獲得數據便可
return;
}
//為上傳表單，則挪用解析器解析上傳數據
List<FileItem> list = upload.parseRequest(request); //FileItem
//遍歷list，獲得用於封裝第一個上傳輸出項數據fileItem對象
for(FileItem item : list){
if(item.isFormField()){
//獲得的是通俗輸出項
String name = item.getFieldName(); //獲得輸出項的稱號
String value = item.getString();
System.out.println(name + "=" + value);
}else{
//獲得上傳輸出項
String filename = item.getName(); //獲得上傳文件名 C:\Documents and Settings\ThinkPad\桌面\1.txt
filename = filename.substring(filename.lastIndexOf("\\")+1);
InputStream in = item.getInputStream(); //獲得上傳數據
int len = 0;
byte buffer[]= new byte[1024];
//用於保留上傳文件的目次應當制止外界直接拜訪
String savepath = this.getServletContext().getRealPath("/WEB-INF/upload");
System.out.println(savepath);
FileOutputStream out = new FileOutputStream(savepath + "/" + filename); //向upload目次中寫入文件
while((len=in.read(buffer))>0){
out.write(buffer, 0, len);
}
in.close();
out.close();
request.setAttribute("message", "上傳勝利");
}
}
}catch (Exception e) {
request.setAttribute("message", "上傳掉敗");
e.printStackTrace();
}
}
2. 修正後的上傳功效：
留意事項：
1、上傳文件名的中文亂碼和上傳數據的中文亂碼
upload.setHeaderEncoding("UTF-8"); //處理上傳文件名的中文亂碼
//表單為文件上傳，設置request編碼有效,只妙手工轉換
1.1 value = new String(value.getBytes("iso8859-1"),"UTF-8");
1.2 String value = item.getString("UTF-8");
2.為包管辦事器平安，上傳文件應當放在外界沒法直接拜訪的目次
3、為避免文件籠罩的景象產生，要為上傳文件發生一個獨一的文件名
4、為避免一個目次上面湧現太多文件，要應用hash算法打散存儲
5.要限制上傳文件的最年夜值，可以經由過程：ServletFileUpload.setFileSizeMax(1024)辦法完成，並經由過程捕捉：
FileUploadBase.FileSizeLimitExceededException異常以給用戶友愛提醒
6.想確保暫時文件被刪除，必定要在處置完上傳文件後，挪用item.delete辦法
7.要限止上傳文件的類型：在收到上傳文件名時，斷定後綴名能否正當
8、監聽文件上傳進度：
ServletFileUpload upload = new ServletFileUpload(factory);
upload.setProgressListener(new ProgressListener(){
public void update(long pBytesRead, long pContentLength, int arg2) {
System.out.println("文件年夜小為：" + pContentLength + ",以後已處置：" + pBytesRead);
}
});
9. 在web頁面中靜態添加文件上傳輸出項
function addinput(){
var div = document.getElementById("file");
var input = document.createElement("input");
input.type="file";
input.name="filename";
var del = document.createElement("input");
del.type="button";
del.value="刪除";
del.onclick = function d(){
this.parentNode.parentNode.removeChild(this.parentNode);
}
var innerdiv = document.createElement("div");
innerdiv.appendChild(input);
innerdiv.appendChild(del);
div.appendChild(innerdiv);
}
上傳jsp:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'upload2.jsp' starting page</title>
<script type="text/javascript">
function addinput(){
var div = document.getElementById("file");
var input = document.createElement("input");
input.type="file";
input.name="filename";
var del = document.createElement("input");
del.type="button";
del.value="刪除";
del.onclick = function d(){
this.parentNode.parentNode.removeChild(this.parentNode);
}
var innerdiv = document.createElement("div");
innerdiv.appendChild(input);
innerdiv.appendChild(del);
div.appendChild(innerdiv);
}
</script>
</head>
<body>
<form action="" enctype="mutlipart/form-data"></form>
<table>
<tr>
<td>上傳用戶：</td>
<td><input type="text" name="username"></td>
</tr>
<tr>
<td>上傳文件：</td>
<td>
<input type="button" value="添加上傳文件" onclick="addinput()">
</td>
</tr>
<tr>
<td></td>
<td>
<div id="file">
</div>
</td>
</tr>
</table>
</body>
</html>
上傳servlet
public class UploadServlet1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//request.getParameter("username"); //****毛病
request.setCharacterEncoding("UTF-8"); //表單為文件上傳，設置request編碼有效
//獲得上傳文件的保留目次
String savePath = this.getServletContext().getRealPath("/WEB-INF/upload");
try{
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setRepository(new File(this.getServletContext().getRealPath("/WEB-INF/temp")));
ServletFileUpload upload = new ServletFileUpload(factory);
/*upload.setProgressListener(new ProgressListener(){
public void update(long pBytesRead, long pContentLength, int arg2) {
System.out.println("文件年夜小為：" + pContentLength + ",以後已處置：" + pBytesRead);
}
});*/
upload.setHeaderEncoding("UTF-8"); //處理上傳文件名的中文亂碼
if(!upload.isMultipartContent(request)){
//依照傳統方法獲得數據
return;
}
/*upload.setFileSizeMax(1024);
upload.setSizeMax(1024*10);*/
List<FileItem> list = upload.parseRequest(request);
for(FileItem item : list){
if(item.isFormField()){
//fileitem中封裝的是通俗輸出項的數據
String name = item.getFieldName();
String value = item.getString("UTF-8");
//value = new String(value.getBytes("iso8859-1"),"UTF-8");
System.out.println(name + "=" + value);
}else{
//fileitem中封裝的是上傳文件
String filename = item.getName(); //分歧的閱讀器提交的文件是紛歧樣 c:\a\b\1.txt 1.txt
System.out.println(filename);
if(filename==null || filename.trim().equals("")){
continue;
}
filename = filename.substring(filename.lastIndexOf("\\")+1);
InputStream in = item.getInputStream();
String saveFilename = makeFileName(filename); //獲得文件保留的稱號
String realSavePath = makePath(saveFilename, savePath); //獲得文件的保留目次
FileOutputStream out = new FileOutputStream(realSavePath + "\\" + saveFilename);
byte buffer[] = new byte[1024];
int len = 0;
while((len=in.read(buffer))>0){
out.write(buffer, 0, len);
}
in.close();
out.close();
item.delete(); //刪除暫時文件
}
}
}catch (FileUploadBase.FileSizeLimitExceededException e) {
e.printStackTrace();
request.setAttribute("message", "文件超越最年夜值！！！");
request.getRequestDispatcher("/message.jsp").forward(request, response);
return;
}
catch (Exception e) {
e.printStackTrace();
}
}
public String makeFileName(String filename){ //2.jpg
return UUID.randomUUID().toString() + "_" + filename;
}
public String makePath(String filename,String savePath){
int hashcode = filename.hashCode();
int dir1 = hashcode&0xf; //0--15
int dir2 = (hashcode&0xf0)>>4; //0-15
String dir = savePath + "\\" + dir1 + "\\" + dir2; //upload\2\3 upload\3\5
File file = new File(dir);
if(!file.exists()){
file.mkdirs();
}
return dir;
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
3. 下載功效
//列出網站一切下載文件
public class ListFileServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String filepath = this.getServletContext().getRealPath("/WEB-INF/upload");
Map map = new HashMap();
listfile(new File(filepath),map);
request.setAttribute("map", map);
request.getRequestDispatcher("/listfile.jsp").forward(request, response);
}
public void listfile(File file,Map map){
if(!file.isFile()){
File files[] = file.listFiles();
for(File f : files){
listfile(f,map);
}
}else{
String realname = file.getName().substring(file.getName().indexOf("_")+1); //9349249849-88343-8344_阿_凡_達.avi
map.put(file.getName(), realname);
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
jsp顯示
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'listfile.jsp' starting page</title>
</head>
<body>
<c:forEach var="me" items="${map}">
<c:url value="/servlet/DownLoadServlet" var="downurl">
<c:param name="filename" value="${me.key}"></c:param>
</c:url>
${me.value } <a href="${downurl}">下載</a> <br/>
</c:forEach>
</body>
</html>
下載處置servlet
public class DownLoadServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String filename = request.getParameter("filename"); //23239283-92489-阿凡達.avi
filename = new String(filename.getBytes("iso8859-1"),"UTF-8");
String path = makePath(filename,this.getServletContext().getRealPath("/WEB-INF/upload"));
File file = new File(path + "\\" + filename);
if(!file.exists()){
request.setAttribute("message", "您要下載的資本已被刪除！！");
request.getRequestDispatcher("/message.jsp").forward(request, response);
return;
}
String realname = filename.substring(filename.indexOf("_")+1);
response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));
FileInputStream in = new FileInputStream(path + "\\" + filename);
OutputStream out = response.getOutputStream();
byte buffer[] = new byte[1024];
int len = 0;
while((len=in.read(buffer))>0){
out.write(buffer, 0, len);
}
in.close();
out.close();
}
public String makePath(String filename,String savePath){
int hashcode = filename.hashCode();
int dir1 = hashcode&0xf; //0--15
int dir2 = (hashcode&0xf0)>>4; //0-15
String dir = savePath + "\\" + dir1 + "\\" + dir2; //upload\2\3 upload\3\5
File file = new File(dir);
if(!file.exists()){
file.mkdirs();
}
return dir;
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
以上就是本文的全體內容，願望對年夜家的進修有所贊助，也願望年夜家多多支撐。
