为什么我们需要注解“RequestParam()”

Question

I'm learning Spring Boot right now, I don't really understand why we need this annotation. In my opinion, this annotation is used to rename.

public String home(@RequestParam("name") String othername, HttpSession session){
          
          session.setAttribute("name", othername);
          return "home.jsp"

}

So if the above code is running, I can pass my name like this: http://127.0.0.1:8080/home?name=bob

But if I don't have the annotation, I can only do http://127.0.0.1:8080/home?othername=bob , why we don't just change the name of the parameter? I think I might misunderstand the concept of RequestParam.

Answer 1

If you only have a handful of request parameters with default behaviour and you can easily name them as you wish, then you are right, the RequestParam annotation is not strictly necessary. However, as soon as you add PathVariables in the mix, or a request parameter eg is not required anymore, but optional, you have to add the annotation there again. Handling the parameter names is just one small aspect of that annotation. Additionally, you might have to implement a legacy API, where the parameter names on the ReST API level cannot be changed, but you want to have a better name in your code for readability, clean code or other reasons.

Answer 2

You did not misunderstand the concept but your knowledge about it is limited.

• It is correct that @RequestParam can be used to rename the request parameter. Why we don't just change the name of the parameter? What if you want to have a parameter name as "package", you cannot just change the variable name to package as it is java reserved keyword, but you can have it as @RequestParam(name = "package") String othername .

Renaming is just one use case of @RequestParam some of the other uses are:

• Differentiates between @RequestParam and @PathVariable variables
• Make a parameter optional with required attribute @RequestParam(required = false) .
• Add a default value for the request parameter @RequestParam(defaultValue = "test") .
• Better code readability.