jfreeChart 序列化问题怎么解决?

jfreeChart 序列化问题怎么解决?
java.lang.IllegalArgumentException: Attribute [JFreeChart_Deleter] is not serializable 
at org.apache.catalina.cluster.session.DeltaSession.setAttribute(DeltaSession.java:1253) 
at org.apache.catalina.cluster.session.DeltaSession.setAttribute(DeltaSession.java:1231) 
at org.apache.catalina.cluster.session.DeltaSessionFacade.setAttribute(DeltaSessionFacade.java:131) 
at org.jfree.chart.servlet.ServletUtilities.registerChartForDeletion(ServletUtilities.java:307) 
at org.jfree.chart.servlet.ServletUtilities.saveChartAsPNG(ServletUtilities.java:192) 
at com.cdg.isp.chart.command.BankChartCommand.generateStepRendererChart(BankChartCommand.java:214) 
at com.cdg.isp.chart.command.BankChartCommand.execute(BankChartCommand.java:125) 
at com.cdg.isp.core.MainServlet.perform(MainServlet.java:58) 
at com.cdg.isp.core.MainServlet.doPost(MainServlet.java:38) 
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710) 
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269) 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) 
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) 
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174) 
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) 
at org.apache.catalina.cluster.tcp.ReplicationValve.invoke(ReplicationValve.java:347) 
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117) 
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108) 
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174) 
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874) 
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665) 
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528) 
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81) 
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689) 
at java.lang.Thread.run(Thread.java:595)