I have such Spring MVC Controller:
@Controller
@RequestMapping(value = "/user")
public class UserController {
.....
@Cacheable(value = "users", key = "#id")
@RequestMapping(value = "/get", method = RequestMethod.GET)
@ResponseBody
public User getUser(Long id){
return userService.get(id);
}
....
}
I want to add header Last-Modified to HTTP Response of GetUser web service.
How can I get proper date when cache was added to my store?
How can I add header Last-Modified with this date to response of my Spring Controller Method?
Spring has an already build in support to handle the last-modified
and If-Modified-Since
header in for driven request handler methods.
It is based on WebRequest.checkNotModified(long lastModifiedTimestamp)
This example is just taken from the java doc:
This will also transparently set the appropriate response headers, for both the modified case and the not-modified case. Typical usage:
@RequestMapping(value = "/get", method = RequestMethod.GET)
public String myHandleMethod(WebRequest webRequest, Model model) {
long lastModified = // application-specific calculation
if (request.checkNotModified(lastModified)) {
// shortcut exit - no further processing necessary
return null;
}
// further request processing, actually building content
model.addAttribute(...);
return "myViewName";
}
But your @Cacheable
annotation is a problem, because it prevent that the method is executed (for the second invocation) and therefore the request.checkNotModified
is not invoked. - If the caching is important then you could remove the @Cacheable
annotation from the controller method and put it on an inner method that is invoked after request.checkNotModified
is done.
//use selfe in order to use annotation driven advices
@Autowire
YourController selfe;
@RequestMapping(value = "/get", method = RequestMethod.GET)
public String myHandleMethod(WebRequest webRequest, Model model) {
long lastModified = // application-specific calculation
if (request.checkNotModified(lastModified)) {
// shortcut exit - no further processing necessary
return null;
} else {
return selfe.innerMyHandleMethod(model);
}
}
@Cacheable(value = "users", key = "#id")
public String innerMyHandleMethod(Model model) {
model.addAttribute(...);
return "myViewName";
}