SpringBoot 2 - OncePerRequestFilter - modify response Headers after processing of Controller - spring

Question

Hello I want to modify some of my API's response Headers after I have completed processing (executed logic) and have concluded with an HTTP status code.
For example if the response is 404, then include specific for example Cache-Control Headers example dont cache, or something like that.
I have already 2 OncePerRequestFilter registered, which work fine - but obviously I can not do logic - once the processing is complete. The CacheControlFilter already has logic that adds by default some Cache-Control headers - e.g cache for 15 sec etc. It seems though that this happens (the addition of headers on the response) on a very early stage of the dispatch and when it reaches to the phase of executing the actual Controller/Endpoint and there is an exception or Error that obviously is going to be handled by an advice etc, I can not mutate these already existing headers- that were already added by the filter.
#Bean
public FilterRegistrationBean filterOne() {
Filter filter = new FilterOne();
return createFilter(filter, "FilterOne",List.of("/*"));
}
#Bean
public FilterRegistrationBean cacheControlFilter() {
Filter filter = new CacheControlFilter();
return createFilter(filter, "CacheControlFilter", List.of("/*"));
}
private FilterRegistrationBean createFilter(Filter aFilter, String filterName,
List<String> urlPatterns) {
FilterRegistrationBean filterRegBean = new FilterRegistrationBean(aFilter);
filterRegBean.addUrlPatterns(urlPatterns.toArray(new String[0]));
filterRegBean.setName(filterName);
filterRegBean.setEnabled(true);
filterRegBean.setAsyncSupported(true);
return filterRegBean;
}
I have already tried, to add an HttpServletResponseWrapper as indicated on these post here and here on the CacheControlFilter but it does not seem to work. I have also seen a similar S.O thread here.
HttpServletResponseWrapper wrapper = new HttpServletResponseWrapper(response) {
#Override
public void setStatus(int sc) {
super.setStatus(sc);
handleStatus(sc);
}
#Override
#SuppressWarnings("deprecation")
public void setStatus(int sc, String sm) {
super.setStatus(sc, sm);
handleStatus(sc);
}
#Override
public void sendError(int sc, String msg) throws IOException {
super.sendError(sc, msg);
handleStatus(sc);
}
#Override
public void sendError(int sc) throws IOException {
super.sendError(sc);
handleStatus(sc);
}
private void handleStatus(int code) {
if(code == 404)
addHeader("Cache-Control, "xxx");
}
};
But the code is not executed at all! So I want to manipulate the Cache-Control headers on the second filter only after though the processing is complete and I am ready to return a response.
I am not sure if the fact that I also have, doing some clean up and setting responses upon errors - mixes things up!
#ControllerAdvice
#Slf4j
public class GlobalErrorHandler
Update: As a note, when my Controller is throwing an Exception or Error, the above GlobalErrorHandler is invoked and there I execute a special handling, returning an error response. What I see though is that magically the response has already the default headers populated by the Filter (CacheControlFilter). So it ends up being a bit weird, I add extra logic,to change the control header and I end up with a response that has the same header 2 times (1 with the value set by the CacheControlFilter and then any special value I am trying to override on the ControllerAdvice
Any tips or help appreciated thanks! I am using Spring Boot 2.1.2 with Undertow as my underlying servlet container.

Answer 1

The link you mentioned says that cannot get the status code or modify the headers in ResponseBodyAdvice is not true . If you cast ServerHttpResponse to ServletServerHttpResponse , you can do both of them. So simply implement a ResponseBodyAdvice :
#ControllerAdvice
public class CacheControlBodyAdvice implements ResponseBodyAdvice {
#Override
public boolean supports(MethodParameter returnType, Class converterType) {
return true;
}
#Override
public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,
Class selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {
if(response instanceof ServletServerHttpResponse) {
ServletServerHttpResponse res= (ServletServerHttpResponse)(response);
if(res.getServletResponse().getStatus() == 400){
res.getServletResponse().setHeader("Cache-Control", "XXXXX");
}
}
return body;
}
}
One more thing need to pay attention is that if your controller method throws an exception before complete normally , depending on how to handle the exceptions , the ResponseBodyAdvice may not be trigger. So , I suggest to implement the same logic in the GlobalErrorHandler for safety guard :
#ControllerAdvice
public class GlobalErrorHandler{
#ExceptionHandler(value = Exception.class)
public void handle(HttpServletRequest request, HttpServletResponse response) {
if(response.getStatus() == 400){
response.setHeader("Cache-Control", "XXXXX");
}
}
}

Answer 2

I supposed that you are using spring-mvc (As you mentioned in your tags); If so you can bind to HttpServletResponse to add your headers. You can do it in your method handler like so:
#RestController
class HelloWordController{
#GetMapping("/hello")
public String test(HttpServletResponse response){
response.addHeader("test", "123");
return "hola";
}
}
Another solution (fashion) would be to return a ResponseEntity instead :
#RestController
class HelloWorkController{
#GetMapping("/hello")
public ResponseEntity<String> test(HttpServletResponse response){
return ResponseEntity.status(HttpStatus.OK)
.header("test", "4567")
.body("hello world");
}
}

Answer 3

There are a dozen of ways of changing a HttpServletResponse before return to client in Spring and injecting the response into the handler method or leveraging ControllerAdvice are valid solutions. However, I don't understand the underlying premise of your question that filters can't do the job:
I have already 2 OncePerRequestFilter registered, which work fine -
but obviously I can not do logic - once the processing is complete.
As far as modifying HttpServletResponse is concerned, Filters work totally fine for me and are at least as suitable as any other tool for that job:
#Bean
public FilterRegistrationBean createFilter() {
Filter filter = new OncePerRequestFilter() {
#Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
super.doFilter(request, response, filterChain);
response.setHeader("Cache-Control", "xxx");
}
};
return new FilterRegistrationBean(filter);
}