用JSP实现文件上传功能，参考如下：
UploadExample.jsp
<%@ page contentType="text/html;charset=gb2312"%>
<%= application.getServerInfo() %>上传文件程序应用示例
doUpload.jsp
<%@ page contentType="text/html; charset=GBK" %>
<%@ page import="java.io.*"%>
<%@ page import="java.util.*"%>
<%@ page import="javax.servlet.*"%>
<%@ page import="javax.servlet.http.*"%>
upFile<%
//定义上载文件的最大字节
int MAX_SIZE = 102400 * 102400;
// 创建根路径的保存变量
String rootPath;
//声明文件读入类
DataInputStream in = null;
FileOutputStream fileOut = null;
//取得客户端的网络地址
String remoteAddr = request.getRemoteAddr();
//获得服务器的名字
String serverName = request.getServerName();
//取得互联网程序的绝对地址
String realPath = request.getRealPath(serverName);
realPath = realPath.substring(0,realPath.lastIndexOf("\\"));
//创建文件的保存目录
rootPath = realPath + "\\upload\\";
//取得客户端上传的数据类型
String contentType = request.getContentType();
try{
if(contentType.indexOf("multipart/form-data") >= 0){
//读入上传的数据
in = new DataInputStream(request.getInputStream());
int formDataLength = request.getContentLength();
if(formDataLength > MAX_SIZE){
out.println("
上传的文件字节数不可以超过" + MAX_SIZE + "
");
return;
}
//保存上传文件的数据
byte dataBytes[] = new byte[formDataLength];
int byteRead = 0;
int totalBytesRead = 0;
//上传的数据保存在byte数组
while(totalBytesRead < formDataLength){
byteRead = in.read(dataBytes,totalBytesRead,formDataLength);
totalBytesRead += byteRead;
}
//根据byte数组创建字符串
String file = new String(dataBytes);
//out.println(file);
//取得上传的数据的文件名
String saveFile = file.substring(file.indexOf("filename=\"") + 10);
saveFile = saveFile.substring(0,saveFile.indexOf("\n"));
saveFile = saveFile.substring(saveFile.lastIndexOf("\\") + 1,saveFile.indexOf("\""));
int lastIndex = contentType.lastIndexOf("=");
//取得数据的分隔字符串
String boundary = contentType.substring(lastIndex + 1,contentType.length());
//创建保存路径的文件名
String fileName = rootPath + saveFile;
//out.print(fileName);
int pos;
pos = file.indexOf("filename=\"");
pos = file.indexOf("\n",pos) + 1;
pos = file.indexOf("\n",pos) + 1;
pos = file.indexOf("\n",pos) + 1;
int boundaryLocation = file.indexOf(boundary,pos) - 4;
//out.println(boundaryLocation);
//取得文件数据的开始的位置
int startPos = ((file.substring(0,pos)).getBytes()).length;
//out.println(startPos);
//取得文件数据的结束的位置
int endPos = ((file.substring(0,boundaryLocation)).getBytes()).length;
//out.println(endPos);
//检查上载文件是否存在
File checkFile = new File(fileName);
if(checkFile.exists()){
out.println("
" + saveFile + "文件已经存在.
");
}
//检查上载文件的目录是否存在
File fileDir = new File(rootPath);
if(!fileDir.exists()){
fileDir.mkdirs();
}
//创建文件的写出类
fileOut = new FileOutputStream(fileName);
//保存文件的数据
fileOut.write(dataBytes,startPos,(endPos - startPos));
fileOut.close();
out.println(saveFile + "文件成功上载.");
}else{
String content = request.getContentType();
out.println("
上传的数据类型不是multipart/form-data
");
}
}catch(Exception ex){
throw new ServletException(ex.getMessage());
}
%>
运行方法，将这两个JSP文件放在同一路径下，运行UploadExample.jsp即可。
