roo java.lang.IllegalStateException: getOutputStream() has already been called for th

When I use roo, often appear to the following questions:


严重: Servlet.service() for servlet hr threw exception
java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(R esponse.java:611)
at org.apache.catalina.connector.ResponseFacade.getWr iter(ResponseFacade.java:198)


Why is there this problem? Who can give me a suggestion ? Thank you very much!