文件上傳在web應用中非常普遍，要在jsp環境中實現文件上傳功能是非常容易的，因為網上有許多用java開發的文件上傳組件，本文以commons-fileupload組件為例，為jsp應用添加文件上傳功能。
common-fileupload組件是apache的一個開源項目之一，可以從http://jakarta.apache.org/commons/fileupload/下載。
用該組件可實現一次上傳一個或多個文件，並可限製文件大小。
下載後解壓zip包，將commons-fileupload-1.0.jar複製到tomcat的webapps你的webappWEB-INFlib下，目錄不存在請自建目錄。
新建一個servlet: Upload.java用於文件上傳：
import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; import org.apache.commons.fileupload.*; public class Upload extends HttpServlet {private String uploadPath = "C:upload"; // 上傳文件的目錄private String tempPath = "C:uploadtmp"; // 臨時文件目錄public void doPost(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException{}}在doPost()方法中，當servlet收到瀏覽器發出的Post請求後，實現文件上傳。以下是示例代碼：
public void doPost(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException{try {DiskFileUpload fu = new DiskFileUpload(); // 設置最大文件尺寸，這裡是4MBfu.setSizeMax(4194304); // 設置緩衝區大小，這裡是4kbfu.setSizeThreshold(4096); // 設置臨時目錄：fu.setRepositoryPath(tempPath); // 得到所有的文件：List fileItems = fu.parseRequest(request); Iterator i = fileItems.iterator(); // 依次處理每一個文件：while(i.hasNext()) {FileItem fi = (FileItem)i.next(); // 獲得文件名，這個文件名包括路徑：String fileName = fi.getName(); // 在這裡可以記錄用戶和文件信息// ...// 寫入文件，暫定文件名為a.txt，可以從fileName中提取文件名：fi.write(new File(uploadPath + "a.txt")); }}catch(Exception e) {// 可以跳轉出錯頁面}}如果要在配置文件中讀取指定的上傳文件夾，可以在init()方法中執行：
public void init() throws ServletException {uploadPath = ....tempPath = ....// 文件夾不存在就自動創建：if(!new File(uploadPath).isDirectory())new File(uploadPath).mkdirs(); if(!new File(tempPath).isDirectory())new File(tempPath).mkdirs(); }編譯該servlet，注意要指定classpath，確保包含commons-upload-1.0.jar和tomcatcommonlibservlet-api.jar。
配置servlet，用記事本打開tomcatwebapps你的webappWEB-INFweb.xml，沒有的話新建一個。
典型配置如下：
〈?xml version="1.0" encoding="ISO-8859-1"?〉〈!DOCTYPE web-appPUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN""http://java.sun.com/dtd/web-app_2_3.dtd"〉〈web-app〉〈servlet〉〈servlet-name〉Upload〈/servlet-name〉〈servlet-class〉Upload〈/servlet-class〉〈/servlet〉〈servlet-mapping〉〈servlet-name〉Upload〈/servlet-name〉〈url-pattern〉/fileupload〈/url-pattern〉〈/servlet-mapping〉〈/web-app〉
配置好servlet後，啟動tomcat，寫一個簡單的html測試：
〈form action="fileupload" method="post"enctype="multipart/form-data" name="form1"〉〈input type="file" name="file"〉〈input type="submit" name="Submit" value="upload"〉〈/form〉
注意action="fileupload"其中fileupload是配置servlet時指定的url-pattern。
下面是某個大蝦的代碼：
這個Upload比smartUpload好用多了.完全是我一個個byte調試出來的,不像smartUpload的bug具多.
調用方法:
Upload up = new Upload(); up.init(request); /**此處可以調用setSaveDir(String saveDir); 設置保存路徑調用setMaxFileSize(long size)設置上傳文件的最大字節.調用setTagFileName(String)設置上傳後文件的名字(只對第一個文件有效)*/up. uploadFile();
然後String[] names = up.getFileName(); 得到上傳的文件名,文件絕對路徑應該是
保存的目錄saveDir+"/"+names[i];
可以通過up.getParameter("field"); 得到上傳的文本或up.getParameterValues("filed")
得到同名字段如多個checkBox的值.
其它的自己試試.
源碼如下所示:____________________________________________________________
package com.inmsg.beans; import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public class Upload {private String saveDir = "."; //要保存文件的路徑private String contentType = ""; //文檔類型private String charset = ""; //字符集private ArrayList tmpFileName = new ArrayList(); //臨時存放文件名的數據結構private Hashtable parameter = new Hashtable(); //存放參數名和值的數據結構private ServletContext context; //程序上下文,用於初始化private HttpServletRequest request; //用於傳入請求對象的實例private String boundary = ""; //內存數據的分隔符private int len = 0; //每次從內在中實際讀到的字節長度private String queryString; private int count; //上載的文件總數private String[] fileName; //上載的文件名數組private long maxFileSize = 1024 * 1024 * 10; //最大文件上載字節; private String tagFileName = ""; public final void init(HttpServletRequest request) throws ServletException {this.request = request; boundary = request.getContentType().substring(30); //得到內存中數據分界符queryString = request.getQueryString(); }public String getParameter(String s) { //用於得到指定字段的參數值,重寫request.getParameter(String s)if (parameter.isEmpty()) {return null; }return (String) parameter.get(s); }public String[] getParameterValues(String s) { //用於得到指定同名字段的參數數組,重寫request.getParameterValues(String s)ArrayList al = new ArrayList(); if (parameter.isEmpty()) {return null; }Enumeration e = parameter.keys(); while (e.hasMoreElements()) {String key = (String) e.nextElement(); if ( -1 != key.indexOf(s + "||||||||||") || key.equals(s)) {al.add(parameter.get(key)); }}if (al.size() == 0) {return null; }String[] value = new String[al.size()]; for (int i = 0; i 〈 value.length; i++) {value[i] = (String) al.get(i); }return value; }public String getQueryString() {return queryString; }public int getCount() {return count; }public String[] getFileName() {return fileName; }public void setMaxFileSize(long size) {maxFileSize = size; }public void setTagFileName(String filename) {tagFileName = filename; }public void setSaveDir(String saveDir) { //設置上載文件要保存的路徑this.saveDir = saveDir; File testdir = new File(saveDir); //為了保證目錄存在,如果沒有則新建該目錄if (!testdir.exists()) {testdir.mkdirs(); }}public void setCharset(String charset) { //設置字符集this.charset = charset; }public boolean uploadFile() throws ServletException, IOException { //用戶調用的上載方法setCharset(request.getCharacterEncoding()); return uploadFile(request.getInputStream()); }private boolean uploadFile(ServletInputStream servletinputstream) throws //取得央存數據的主方法ServletException, IOException {String line = null; byte[] buffer = new byte[256]; while ( (line = readLine(buffer, servletinputstream, charset)) != null) {if (line.startsWith("Content-Disposition: form-data; ")) {int i = line.indexOf("filename="); if (i 〉= 0) { //如果一段分界符內的描述中有filename=,說明是文件的編碼內容String fName = getFileName(line); if (fName.equals("")) {continue; }if (count == 0 && tagFileName.length() != 0) {String ext = fName.substring( (fName.lastIndexOf(".") + 1)); fName = tagFileName + "." + ext; }tmpFileName.add(fName); count++; while ( (line = readLine(buffer, servletinputstream, charset)) != null) {if (line.length() 〈= 2) {break; }}File f = new File(saveDir, fName); FileOutputStream dos = new FileOutputStream(f); long size = 0l; while ( (line = readLine(buffer, servletinputstream, null)) != null) {if (line.indexOf(boundary) != -1) {break; }size += len; if (size 〉 maxFileSize) {throw new IOException("文件超過" + maxFileSize + "字節!"); }dos.write(buffer, 0, len); }dos.close(); }else { //否則是字段編碼的內容String key = getKey(line); String value = ""; while ( (line = readLine(buffer, servletinputstream, charset)) != null) {if (line.length() 〈= 2) {break; }}while ( (line = readLine(buffer, servletinputstream, charset)) != null) {if (line.indexOf(boundary) != -1) {break; }value += line; }put(key, value.trim(), parameter); }}}if (queryString != null) {String[] each = split(queryString, "&"); for (int k = 0; k 〈 each.length; k++) {String[] nv = split(each[k], "="); if (nv.length == 2) {put(nv[0], nv[1], parameter); }}}fileName = new String[tmpFileName.size()]; for (int k = 0; k 〈 fileName.length; k++) {fileName[k] = (String) tmpFileName.get(k); //把ArrayList中臨時文件名倒入數據中供用戶調用}if (fileName.length == 0) {return false; //如果fileName數據為空說明沒有上載任何文件}return true; }private void put(String key, String value, Hashtable ht) {if (!ht.containsKey(key)) {ht.put(key, value); }else { //如果已經有了同名的KEY,就要把當前的key更名,同時要注意不能構成和KEY同名try {Thread.currentThread().sleep(1); //為了不在同一ms中產生兩個相同的key}catch (Exception e) {}key += "||||||||||" + System.currentTimeMillis(); ht.put(key, value); }}/*調用ServletInputstream.readLine(byte[] b,int offset,length)方法,該方法是從ServletInputstream流中讀一行到指定的byte數組,為了保證能夠容納一行,該byte[]b不應該小於256,重寫的readLine中,調用了一個成員變量len為實際讀到的字節數(有的行不滿256),則在文件內容寫入時應該從byte數組中寫入這個len長度的字節而不是整個byte[]的長度,但重寫的這個方法返回的是String以便分析實際內容,不能返回len,所以把len設為成員變量,在每次讀操作時把實際長度賦給它.也就是說在處理到文件的內容時數據既要以String形式返回以便分析開始和結束標記,又要同時以byte[]的形式寫到文件輸出流中.*/private String readLine(byte[] Linebyte,ServletInputStream servletinputstream, String charset) {try {len = servletinputstream.readLine(Linebyte, 0, Linebyte.length); if (len == -1) {return null; }if (charset == null) {return new String(Linebyte, 0, len); }else {return new String(Linebyte, 0, len, charset); }}catch (Exception _ex) {return null; }}private String getFileName(String line) { //從描述字符串中分離出文件名if (line == null) {return ""; }int i = line.indexOf("filename="); line = line.substring(i + 9).trim(); i = line.lastIndexOf(""); if (i 〈 0 || i 〉= line.length() - 1) {i = line.lastIndexOf("/"); if (line.equals("""")) {return ""; }if (i 〈 0 || i 〉= line.length() - 1) {return line; }}return line.substring(i + 1, line.length() - 1); }private String getKey(String line) { //從描述字符串中分離出字段名if (line == null) {return ""; }int i = line.indexOf("name="); line = line.substring(i + 5).trim(); return line.substring(1, line.length() - 1); }public static String[] split(String strOb, String mark) {if (strOb == null) {return null; }StringTokenizer st = new StringTokenizer(strOb, mark); ArrayList tmp = new ArrayList(); while (st.hasMoreTokens()) {tmp.add(st.nextToken()); }String[] strArr = new String[tmp.size()]; for (int i = 0; i 〈 tmp.size(); i++) {strArr[i] = (String) tmp.get(i); }return strArr; }}下載其實非常簡單，只要如下處理，就不會發生問題。 public void downLoad(String filePath,HttpServletResponse response,boolean isOnLine)throws Exception{File f = new File(filePath); if(!f.exists()){response.sendError(404,"File not found!"); return; }BufferedInputStream br = new BufferedInputStream(new FileInputStream(f)); byte[] buf = new byte[1024]; int len = 0; response.reset(); //非常重要if(isOnLine){ //在線打開方式URL u = new URL("file:///"+filePath); response.setContentType(u.openConnection().getContentType()); response.setHeader("Content-Disposition", "inline; filename="+f.getName()); //文件名應該編碼成UTF-8}else{ //純下載方式response.setContentType("application/x-msdownload"); response.setHeader("Content-Disposition", "attachment; filename=" + f.getName()); }OutputStream out = response.getOutputStream(); while((len = br.read(buf)) 〉0)out.write(buf,0,len); br.close(); out.close(); }