Domain class export error

[mikko1986]

Error : org.codehaus.groovy.grails.web.pages.exceptions.GroovyPagesException: Error processing GroovyPageView: getOutputStream() has already been called for this response

Code:

def export() {
    def list = financialSettlementService.getDietitianList(params)
    def headers = ['Tax']
    def withProperties = ['tax']
    new WebXlsxExporter().with {
        setResponseHeaders(response)
        fillHeader(headers)
        add(list, withProperties)
        save(response.outputStream)
    }
}