I find the source code in org.springframework.integration.http.inbound.HttpRequestHandlingEndpointSupport
@SuppressWarnings({ "rawtypes", "unchecked" })
private Message<?> actualDoHandleRequest(HttpServletRequest servletRequest, HttpServletResponse servletResponse) throws IOException {
//omitted codes
LinkedMultiValueMap<String, String> requestParams = this.convertParameterMap(servletRequest.getParameterMap());
evaluationContext.setVariable("requestParams", requestParams);
//omitted codes
}
so the #requestParameters is a LinkedMultiValueMap object. I can use
#requestParams.get('your key')?:''//null safe
to get the desired String request parameter.