getOutputStream() has already been called for this response解决方案

严重: Servlet.service() for servlet jsp threw exceptionjava.lang.IllegalStateException: getOutputStream() has already been called for this response    at org.apache.catalina.connector.Response.getWriter(Response.java:610)    at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)    at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)    at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)    at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:186)    at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:118)    at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:77)    at org.apache.jsp.vcode_jsp._jspService(vcode_jsp.java:149)

public ActionForward doLogin(ActionMapping mapping, ActionForm form,            HttpServletRequest request, HttpServletResponse response) {        // TODO Auto-generated method stub        HttpSession session = request.getSession(true);                DynaActionForm dynaAction = (DynaActionForm)form ;        int petId = ((Integer)dynaAction.get("petId")).intValue();        String password = dynaAction.getString("petPassword");        String vCode2 = dynaAction.getString("valiCode");        String vCode1 = (String)session.getAttribute("vcode");        PetInfo pet = biz.login(petId, password);                if(pet != null && vCode1.equals(vCode1)){            session.setAttribute("current_pet", pet);            try {                response.sendRedirect("ShowBaby.do?id="+petId);            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }            return null ;        }        ActionMessages errors = new ActionMessages();        if(!vCode1.equals(vCode2)){            errors.add("login_valiCode", new ActionMessage("errors.login.valiCode"));            super.addErrors(request, errors);            return mapping.findForward("fail");        }                errors.add("login_fail", new ActionMessage("errors.login.fail"));        super.saveErrors(request, errors);        return mapping.findForward("fail");