java.lang.IllegalStateException at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFa

严重: Servlet.service() for servlet default threw exception

java.lang.IllegalStateException

at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:407)

at org.apache.struts2.dispatcher.Dispatcher.sendError(Dispatcher.java:839)

at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:533)

at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)

at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:291)

at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)

at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)

at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)

at java.lang.Thread.run(Thread.java:619)

在用action 里返回json 数据时，不能return SUCCESS ，必须return null 否则报此错误!
http://blog.csdn.net/aaa1117a8w5s6d/article/details/8439584