jsp文件上传大多采用开源项目Commons FileUpload来简化处理，可以在http://jakarta.apache.org/commons/fileupload/下载，这个包需要Commons IO的支持，可以在http://jakarta.apache.org/commons/io/下载。Commons FileUpload提供三种文件上传处理方式，DiskFileUpload、ServletFileUpload和 PortletFileUpload三种方式，其中DiskFileUpload已经在javadoc下已经被标记为过期的方法，建议用 ServletFileUpload代替，而PortletFileUpload需要配合portlet-api来使用，所以这里我们只介绍 ServletFileUpload，并且这个也是最常用的。使用如下：
test.jsp：
<%@ page language="java" import="java.util.*" contentType="text/html;charset=gbk" pageEncoding="gbk"%><html> <body> <form action="/MultipartTestServlet" enctype="multipart/form-data" method="post"> <input type="text" name="username" /><br /> <input type="file" name="myfile" /><br/> <input type="file" name="myfile" /><br/> <input type="submit" /> </form> </body></html>
MultipartTestServlet.java：
import java.io.File;import java.io.IOException;import java.util.ArrayList;import java.util.Iterator;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.FileUpload;import org.apache.commons.fileupload.FileUploadException;import org.apache.commons.fileupload.RequestContext;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;import org.apache.commons.fileupload.servlet.ServletRequestContext;public class MultipartTestServlet extends HttpServlet { public MultipartTestServlet() { super(); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); RequestContext requestContext = new ServletRequestContext(request); if(FileUpload.isMultipartContent(requestContext)){ DiskFileItemFactory factory = new DiskFileItemFactory(); factory.setRepository(new File("c:/tmp/")); ServletFileUpload upload = new ServletFileUpload(factory); //upload.setHeaderEncoding("utf-8"); upload.setSizeMax(2000000); List items = new ArrayList(); try { items = upload.parseRequest(request); } catch (FileUploadException e1) { System.out.println("文件上传发生错误" + e1.getMessage()); } Iterator it = items.iterator(); while(it.hasNext()){ FileItem fileItem = (FileItem) it.next(); if(fileItem.isFormField()){ System.out.println(fileItem.getFieldName() + " " + fileItem.getName() + " " + new String (fileItem.getString().getBytes("iso8859-1"), "gbk")); }else{ System.out.println(fileItem.getFieldName() + " " + fileItem.getName() + " " + fileItem.isInMemory() + " " + fileItem.getContentType() + " " + fileItem.getSize()); if(fileItem.getName()!=null && fileItem.getSize()!=0){ File fullFile = new File(fileItem.getName()); File newFile = new File("c:/temp/" + fullFile.getName()); try { fileItem.write(newFile); } catch (Exception e) { e.printStackTrace(); } }else{ System.out.println("文件没有选择 或 文件内容为空"); } } } } }}