求各位高手帮助解决JSP上传文件错误

Question

代码：
<%
//新建一个SmartUpload对象
SmartUpload su = new SmartUpload();
//上传初始化,pageContext为JSP的内置对象
su.initialize(pageContext);
//设定允许上传的文件（通过扩展名限制）,仅允许jpg,bmp,gif文件。
su.setAllowedFilesList("jpg,bmp,gif");
//上传文件
su.upload();
//将上传文件全部保存到指定目录
su.save("/upload",SmartUpload.SAVE_VIRTUAL);
%>错误提示：
org.apache.jasper.JasperException: An exception occurred processing JSP page /uploadFileAccept.jsp at line 1512: //设定允许上传的文件（通过扩展名限制）,仅允许jpg,bmp,gif文件。
13: su.setAllowedFilesList("jpg,bmp,gif");
14: //上传文件
15: su.upload();
16: //将上传文件全部保存到指定目录
17: su.save("/upload",SmartUpload.SAVE_VIRTUAL);
18: %>
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:521)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:430)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
root cause java.lang.NegativeArraySizeException
com.jspsmart.upload.SmartUpload.upload(SmartUpload.java:218)
org.apache.jsp.uploadFileAccept_jsp._jspService(uploadFileAccept_jsp.java:68)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)