jfinal 文件上传问题

本人使用jfinal上传图片。由于用户手册没有给出详细的说明，所以不知道解决。
前台代码如下：

<form action="/admin/team/addsave" method="post" id="myform" name="myform" enctype="multipart/form-data">
                    <table class="insert-tab" width="100%">
                        <tbody>
                            <tr>
                                <th><i class="require-red">*</i>缩略图：</th>
                                <td><input name="img" id="" type="file"></td>
                            </tr>
                            <tr>
                                <th></th>
                                <td>
                                    <input class="btn btn-primary btn6 mr10" value="提交" type="submit">
                                    <input class="btn btn6" onclick="history.go(-1)" value="返回" type="button">
                                </td>
                            </tr>
                        </tbody>
                   </table>
</form>

后台代码：

UploadFile upFile = getFile("img");

控制台报错是：

2016-03-24 15:55:30
[ERROR]-[Thread: qtp927929668-14]-[com.jfinal.core.ActionHandler.handle()]: /admin/team/addsave
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
	at com.jfinal.core.ActionInvocation.invoke(ActionInvocation.java:61)
	at com.jfinal.core.ActionHandler.handle(ActionHandler.java:73)
	at com.jfinal.core.JFinalFilter.doFilter(JFinalFilter.java:72)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1307)
	at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:453)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
	at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:560)
	at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
	at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1072)
	at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:382)
	at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
	at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1006)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
	at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
	at org.eclipse.jetty.server.Server.handle(Server.java:365)
	at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:485)
	at org.eclipse.jetty.server.AbstractHttpConnection.content(AbstractHttpConnection.java:937)
	at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.content(AbstractHttpConnection.java:998)
	at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:856)
	at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:240)
	at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:628)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52)
	at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
	at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.jfinal.core.ActionInvocation.invoke(ActionInvocation.java:55)
	... 25 more
Caused by: java.lang.NoClassDefFoundError: com/oreilly/servlet/multipart/FileRenamePolicy
	at com.jfinal.core.Controller.getFiles(Controller.java:678)
	at com.jfinal.core.Controller.getFile(Controller.java:688)
	at com.wyj.controller.TeamAdminContoller.addsave(TeamAdminContoller.java:29)
	... 30 more
Caused by: java.lang.ClassNotFoundException: com.oreilly.servlet.multipart.FileRenamePolicy
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:430)
	at com.jfinal.server.JFinalClassLoader.loadClass(JFinalClassLoader.java:53)
	... 33 more

求高手指点怎么解决。