Injecting in HttpServletRequest to a Spring Bean

This is a little counter intuitive, you can actually inject in HttpServletRequest into any Spring component!

For eg:

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import javax.servlet.http.HttpServletRequest;   import org.springframework.beans.factory.annotation.Autowired;   public class HttpRequestServiceImpl implements HttpRequestService{    @Autowired private HttpServletRequest httpServletRequest;  @Override  public String getAttribute(String name) {   return (String)this.httpServletRequest.getAttribute(name);  } }

So when multiple requests come to this service, how is the correct httpServletRequest corresponding to the user request injected into this service object. The answer is that a real HttpServletRequest is not really injected, only a proxy is injected in. The proxy is internally a reference to RequestContextHolder which at some point binds the HttpServletRequest to a threadlocal variable.