Preface

Spring MVC analyzes the signature of a handler method and binds HTTP request information to the corresponding parameters of that method. In a new project I recently took over, they put a lot of commonly used info into headers, so I ended up using the @RequestHeader annotation. It’s pretty ordinary and I don’t use it that often, but it suddenly occurred to me that I should summarize it.

Of course, Spring MVC is very flexible about controller method signatures—you can pretty much define them however you like and still get the parameters you need.

Main Content

The more commonly used ways to get parameters at work:

• @PathVariable

  This is a commonly used parameter in RESTful APIs. The value corresponds to the part inside {} in the endpoint URL, and it can be used to retrieve parameters from the URL.
  

• @RequestParam

  This used to be a pretty common annotation for receiving parameters from the frontend, mainly for handling content encoded with the default HTTP content-type.
  // By default, the parameters are of type application/x-www-form-urlencoded
  

• @RequestBody

  This is a more popular way to receive parameters nowadays, generally used to handle data that is not encoded as Content-Type: application/x-www-form-urlencoded.
  The most common one is JSON, of course.
  

• @RequestHeader

  This is the annotation I’ve been using a lot recently, because my company puts the user’s userid and userkey in the header as required fields for every request message,
  so I often use this annotation to receive them.
  

• @CookieValue

  This is used similarly to @RequestParam, except it retrieves values from cookies. It’s actually very convenient—much more elegant than pulling it out manually in code.
  

  For most of the annotations above, besides the value, there’s also a required field. It defaults to true, meaning an exception will be thrown if the client doesn’t provide it. In practice, we usually change it to false manually—of course, because we’d rather return a friendly error message from our code.

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