Spring MVC - Can I autowire HttpServletRequest in RestController

Question

Can I autowire HttpServletRequest in my RestController like following and will it returns different servletRequest even if it is executed in highly concurrent environment. I have a restriction that I can not have as method parameter because I am implementing an interface which is auto generated and will not have HttpServletRequest as the method parameter.

@RestController
public class MyController implements MyInterface {
        
    @Autowired
    private HttpServletRequest servletRequest;
        
    @Override
    @RequestMapping(value = "/test", produces = {"application/json"}, consumes = {"application/json"}, method = RequestMethod.POST)
    public ResponseEntity<MyResponse> test(@RequestBody final MyRequest payload){
        ...
    }
    ...
}

I have gone through these SO questions and some other articles on this. But just wanted to ensure that when we autowire HttpServletRequest in the controller then its Scope is Request?

Spring 3 MVC accessing HttpRequest from controller

How are Threads allocated to handle Servlet request?

Scope of a Spring-Controller and its instance-variables

How do I get a HttpServletRequest in my spring beans?

How To Get HTTP Request Header In Java

Note: I did try this and it seems to work fine. But just wanted to confirm that it's a foolproof solution even in a highly concurrent environment. Also if this is the correct way to do it, I would appreciate if someone can explain how exactly it works.

Why not `public ResponseEntity test(@RequestBody final MyRequest payload, HttpServletRequest request) {...}`? Wouldn't Spring inject the request automatically? — lealceldeiro, Apr 05 '18 at 20:09
I did mention that in my question that I cannot do that. Because I need to implement `MyInterface` in my `RestController` which is auto generated from a Spec and it cannot have `HttpServletRequest ` as the method parameter. — Learner, Apr 05 '18 at 20:31

score 9 · Accepted Answer · answered Apr 11 '18 at 20:26

I have used this and it works fine. But unfortunately I did not find any official documentation which mentions that this should work.

Here is the explanation based on my understanding from debugging the code with running multiple requests with different headers/payload etc.:

Whether we autowire on field or through the constructor, servletRequest acts like a Proxy object which delegates the call to Current HttpServletRequest which is different for each request. Thus, even though it's injected through constructor in a Singleton RestController, it will still have the call delegated to corresponding HttpServletRequest for each new request. This utilizes AutowireUtils.ObjectFactoryDelegatingInvocationHandler to access the current HttpServletRequest object. The java doc for it also says Reflective InvocationHandler for lazy access to the current target object.

Thus even if the autowired Proxy object is always the same for all requests, the underlying target object to which the call is delegated is the current HttpServletRequest object which is per-request.

There is another way you can get HttpServletRequest is using RequestContextHolder as mentioned in this answer

HttpServletRequest currentRequest = 
((ServletRequestAttributes) RequestContextHolder.currentRequestAttributes())
.getRequest();

Note: As this explanation is based on my understanding, please do share any official documentation about this if anyone has it.

Spring MVC - Can I autowire HttpServletRequest in RestController

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