说明：需要添加commons-fileupload-1.2.2.jar和commons-io-2.4.jar
操作的示例代码如下：
<%
FileItem item = (FileItem)iter,next();
if(!item.isFormFileld()){
String filename=item.getName();
//通过Arrays类的asList()方法创建固定长度的集合
List<String> fileType = Arrays.asList("gif","bmp","jpg");
String ext = fileName.substring(fileName.lastIndexOf(".")+1);
if(!fileType.contains(ext)){
out.print("上传文件失败，文件类型只能为gif,bmp,jpg");
}else{
if(fileName!= null && !fileName.equals("")){
File fullFile = new File(item.getName());
File saveFile = new File(uploadFilePath,fullFile.getName());
item.wrtie(saveFile );
uploadFileName = fullFile.getName();
out.print("上传后的文件名是："+uploadFileName);
}
}
}
%>