java.lang.IllegalStateException: getOutputStream() has already been called for this response

Boa tarde,

Estou gerando um arquivo excel com Apache POI + PrimeFaces, porém estou recebendo o erro abaixo, porém o arquivo está sendo gerado normalmente, sem nenhum erro, o que poderia estar ocasionando isso?

> Grave:   Error Rendering View[/pagina/departamentos/List.xhtml]
> java.lang.IllegalStateException: getOutputStream() has already been called for this response
> 	at org.apache.catalina.connector.Response.getWriter(Response.java:735)
> 	at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:221)
> 	at com.sun.faces.context.ExternalContextImpl.getResponseOutputWriter(ExternalContextImpl.java:1006)
> 	at javax.faces.context.ExternalContextWrapper.getResponseOutputWriter(ExternalContextWrapper.java:828)
> 	at com.sun.faces.application.view.FaceletViewHandlingStrategy.createResponseWriter(FaceletViewHandlingStrategy.java:1175)
> 	at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:438)
> 	at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:194)
> 	at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:151)
> 	at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:126)
> 	at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
> 	at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:223)
> 	at javax.faces.webapp.FacesServlet.service(FacesServlet.java:671)
> 	at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1580)
> 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:338)
> 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
> 	at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:100)
> 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:250)
> 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
> 	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
> 	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
> 	at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:652)
> 	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:591)
> 	at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
> 	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
> 	at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:371)
> 	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:238)
> 	at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:463)
> 	at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:168)
> 	at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
> 	at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
> 	at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:242)
> 	at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
> 	at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
> 	at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:539)
> 	at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
> 	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
> 	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
> 	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
> 	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:593)
> 	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:573)
> 	at java.lang.Thread.run(Thread.java:748)
> 
> Informações:   Exception when handling error trying to reset the response.
> java.lang.IllegalStateException: getOutputStream() has already been called for this response
> 	at org.apache.catalina.connector.Response.getWriter(Response.java:735)
> 	at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:221)
> 	at com.sun.faces.context.ExternalContextImpl.getResponseOutputWriter(ExternalContextImpl.java:1006)
> 	at javax.faces.context.ExternalContextWrapper.getResponseOutputWriter(ExternalContextWrapper.java:828)
> 	at com.sun.faces.application.view.FaceletViewHandlingStrategy.createResponseWriter(FaceletViewHandlingStrategy.java:1175)
> 	at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:438)
> 	at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:194)
> 	at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:151)
> 	at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:126)
> 	at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
> 	at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:223)
> 	at javax.faces.webapp.FacesServlet.service(FacesServlet.java:671)
> 	at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1580)
> 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:338)
> 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
> 	at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:100)
> 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:250)
> 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
> 	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
> 	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
> 	at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:652)
> 	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:591)
> 	at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
> 	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
> 	at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:371)
> 	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:238)
> 	at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:463)
> 	at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:168)
> 	at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
> 	at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
> 	at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:242)
> 	at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
> 	at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
> 	at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:539)
> 	at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
> 	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
> 	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
> 	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
> 	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:593)
> 	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:573)
> 	at java.lang.Thread.run(Thread.java:748)
> 
> Advertência:   StandardWrapperValve[Faces Servlet]: Servlet.service() for servlet Faces Servlet threw exception
> java.lang.IllegalStateException: getOutputStream() has already been called for this response
> 	at org.apache.catalina.connector.Response.getWriter(Response.java:735)
> 	at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:221)
> 	at com.sun.faces.context.ExternalContextImpl.getResponseOutputWriter(ExternalContextImpl.java:1006)
> 	at javax.faces.context.ExternalContextWrapper.getResponseOutputWriter(ExternalContextWrapper.java:828)
> 	at com.sun.faces.application.view.FaceletViewHandlingStrategy.createResponseWriter(FaceletViewHandlingStrategy.java:1175)
> 	at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:438)
> 	at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:194)
> 	at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:151)
> 	at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:126)
> 	at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
> 	at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:223)
> 	at javax.faces.webapp.FacesServlet.service(FacesServlet.java:671)
> 	at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1580)
> 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:338)
> 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
> 	at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:100)
> 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:250)
> 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
> 	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
> 	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
> 	at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:652)
> 	at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:591)
> 	at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
> 	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
> 	at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:371)
> 	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:238)
> 	at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:463)
> 	at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:168)
> 	at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
> 	at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
> 	at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:242)
> 	at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
> 	at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
> 	at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
> 	at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:539)
> 	at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
> 	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
> 	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
> 	at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
> 	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:593)
> 	at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:573)
> 	at java.lang.Thread.run(Thread.java:748)

Código responsável por gerar o arquivo:

public void handleFileDownload() throws IOException{
        List<Departamentos> listTmp = getFacade().findAll(getConsultarPor(), getParametroConsulta());
        Workbook workbook = new XSSFWorkbook();
        Sheet sheet = workbook.createSheet("Plan1");
        
        int i = 0;
        for(Departamentos tmp : listTmp) {
            Row row = sheet.createRow(i);
            row.createCell(0).setCellValue(tmp.getDepartamento());
            i++;
        }
            FacesContext facesContext = FacesContext.getCurrentInstance();
            ExternalContext externalContext = facesContext.getExternalContext();
            externalContext.setResponseContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
            externalContext.setResponseHeader("Content-Disposition", "attachment; filename=\"my.xlsx\"");
            
            workbook.write(externalContext.getResponseOutputStream());
            
            workbook.close();
    }

JSP:
<p:commandButton action="#{departamentosController.handleFileDownload}" value="Export" ajax="false"/>