How Do `@RequestParam` and `@PathVariable` Differ in Handling Special Characters in Spring?

Handling Special Characters with @RequestParam and @PathVariable

In web development, handling special characters in request parameters and path variables is crucial. @RequestParam and @PathVariable annotations in Spring Framework provide distinct approaches to managing these characters.

@PathVariable

This annotation binds a URI placeholder to a method parameter. Special characters are treated as part of the path variable value. For instance, in the URL "/user/1234/invoices", the plus sign ( ) represents a literal character.

@RequestParam

In contrast, @RequestParam binds a query parameter to a method parameter. Special characters are typically decoded and interpreted as spaces. For example, in the URL "/user/1234/invoices?date=12-05-2013", the plus sign ( ) is decoded as a space.

Role in Request Parameters and Path Variables

• @PathVariable: Captures URI placeholders, preserving special characters as part of the variable value.
• @RequestParam: Retrieves query parameters from the URI, decoding and interpreting special characters as spaces.

Usage in a Controller Method

Consider a controller method that handles invoices for a user:

@RequestMapping(value="/user/{userId}/invoices", method = RequestMethod.GET)
public List<Invoice> listUsersInvoices(
            @PathVariable("userId") int user,
            @RequestParam(value = "date", required = false) Date dateOrNull) {
  ...
}

Here, the @PathVariable binds the path variable "userId" to the parameter "user", while the @RequestParam retrieves the query parameter "date" into "dateOrNull".

Note: As of Spring 4.3.3, path variables can also be declared as optional, but be cautious of potential URL path hierarchy changes and mapping conflicts.

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