@RequestParam vs. @PathVariable: How Do They Differ When Handling Special Characters in Spring MVC?

Understanding the Differences Between @RequestParam and @PathVariable in Handling Special Characters

When working with special characters in web applications, it is crucial to understand the distinctions between @RequestParam and @PathVariable annotations.

@RequestParam vs. @PathVariable

In Spring MVC applications, @RequestParam is used to extract parameters from the request query string, while @PathVariable is employed to extract placeholders from the URI template. They both serve distinct purposes:

• @RequestParam: Obtains parameters from the URI query string, such as "?param=value". It allows for optional parameters and supports data binding (e.g., converting strings to integers).
• @PathVariable: Extracts placeholders from the URI template, such as "/user/{userId}/invoices". It does not support optional parameters or data binding.

Handling Special Characters

When handling special characters, such as " ", the behavior of @RequestParam and @PathVariable differs:

• @RequestParam: Treats " " as a space character.
• @PathVariable: Preserves " " as a special character.

This difference arises due to the purpose of each annotation. @RequestParam treats parameters as non-path components and may decode special characters to improve usability. Conversely, @PathVariable maintains the integrity of the URI template and does not alter special characters.

Practical Example

Consider the following controller method:

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

With the URL "http://localhost:8080/MyApp/user/1234/invoices?date=12-05-2013", the @RequestParam parameter "date" will be populated with the value "12-05-2013". On the other hand, the @PathVariable "userId" will contain the value 1234, regardless of any special characters in the URI.

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