<form id="uploadFileForm" action="UploadServlet" target="hiddenFrame" method="post" enctype="multipart/form-data">
<input id="fileInput" type="file" onchange="uploadFile();" name="upload" >
<input type="hidden" value="/image/" name="directory">
</form>

package UI.FileManage;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
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.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class UploadServlet extends HttpServlet {

@SuppressWarnings("unchecked")
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
String errorMessage = null;
try {
DiskFileItemFactory fac = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(fac);
upload.setHeaderEncoding("utf-8");
List fileList = null;
fileList = upload.parseRequest(request);

String dir = ((FileItem)fileList.get(1)).getString(); //获取directory参数
if (dir == null) {
dir = "/";
}
String savePath = getServletContext().getRealPath("/test" + dir);
System.out.println("save at:" + savePath);
File f1 = new File(savePath);
if (!f1.exists()) {
f1.mkdirs();
}

Iterator<FileItem> it = fileList.iterator();
String name = "";
while (it.hasNext()) {
FileItem item = it.next();
if (!item.isFormField()) {
name = item.getName();
File file = new File(savePath + File.separatorChar + name);
if (file.exists()) {
errorMessage = "该文件已经存在！请重命名后再上传。";
}
item.write(file);
item.delete(); //释放输出流
}
}
if (errorMessage == null) {
response.getWriter().print("<script> parent.finishUploading(1);</script>");
} else {
response.getWriter().print("<script> parent.finishUploading(0,'" + errorMessage + "');</script>");
}
} catch (Exception exception) {
response.getWriter().print("<script> parent.finishUploading(0,'上传失败，请重试。');</script>");
}
}
}