文件上传前filter出错的问题

兄弟们就是这个错,看了很多资料还是没有解决.求助大家啊
filter和web.xml写在了下面javax.servlet.ServletException: Servlet execution threw an exception
com.SunnyTown.eT.Filters.EncodingFilter.doFilter(EncodingFilter.java:37)
root cause java.lang.NoClassDefFoundError: org/apache/commons/io/output/DeferredFileOutputStream
org.apache.commons.fileupload.DefaultFileItemFactory.createItem(DefaultFileItemFactory.java:103)
org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:350)
org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:302)
org.apache.struts.upload.CommonsMultipartRequestHandler.handleRequest(CommonsMultipartRequestHandler.java:193)
org.apache.struts.util.RequestUtils.populate(RequestUtils.java:443)
org.apache.struts.action.RequestProcessor.processPopulate(RequestProcessor.java:805)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:203)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
com.SunnyTown.eT.Filters.EncodingFilter.doFilter(EncodingFilter.java:37)
以下是我的filter:
public void doFilter(ServletRequest srequest, ServletResponse sresponse,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest request=(HttpServletRequest)srequest;
String contentType=srequest.getContentType();
 if (request.getCharacterEncoding() != null) {
            if ( (contentType != null) &&
                contentType.startsWith("multipart/form-data")) {             } else {
             request.setCharacterEncoding(targetEncoding);
            }
        }      System.out.print("encoding="+targetEncoding);
错误就出现在这里>>>>chain.doFilter(srequest, sresponse);
}下面是web.xml
<filter>
<filter-name>encoding</filter-name>
<filter-class>com.SunnyTown.eT.Filters.EncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>gb2312</param-value>
</init-param>
</filter> <filter-mapping>
    <filter-name>encoding</filter-name>
    <url-pattern>*.do</url-pattern>
    </filter-mapping>这个是form的提交方式
<html:form action="upload.do" method="post" enctype="multipart/form-data">