@RequestParam vs @PathVariable in Spring Boot

1. Introduction

In Spring Boot, @RequestParam and @PathVariable are two annotations used for reading the values of request parameters. @RequestParam is used to extract query parameters from the query string of the HTTP request, while @PathVariable is used to extract values from the URI path.

2. Key Points

1. @RequestParam is used to access the query parameters from the URL (e.g., /api/items?name=Table).

2. @PathVariable is used to extract values from the URI path itself (e.g., /api/items/Table).

3. @RequestParam is typically optional and has a default value if not included in the request.

4. @PathVariable is usually required as part of the URI pattern.

3. Differences

@RequestParam	@PathVariable
Used to extract query parameters from the URL. For example, in /search?name=John, name is a query parameter and can be accessed using @RequestParam.	Used to extract values from the URI path itself. For example, in /users/John, John can be extracted as a path variable using @PathVariable.
Suitable for optional parameters as it allows specifying default values if a parameter is not present in the request.	Typically used for required parameters as part of the URI path, essential for processing the request.
Primarily used in scenarios where the parameter value does not affect the overall URI structure, such as filtering results (/users?role=admin)	Essential for RESTful web services where the URI pattern identifies individual resources (/users/{userId}).
Supports multiple values from the same parameter (e.g., ?type=pdf&type=doc can map to a List or an array).	Maps a single URI path segment to a method parameter.
Can be made optional or required. If a parameter is optional, a default value can also be specified.	Considered required by default, but you can set it to optional by using the required attribute of the @PathVariable annotation.

4. Example

@RestController
@RequestMapping("/api/items")
public class ItemController {

    // Using @RequestParam to extract query parameter
    @GetMapping
    public String getItemByName(@RequestParam(name = "name") String name) {
        return "Item requested: " + name;
    }

    // Using @PathVariable to extract from URI path
    @GetMapping("/{name}")
    public String getItemByPath(@PathVariable("name") String name) {
        return "Item requested: " + name;
    }
}

Output:

// No direct output, since this code is part of a Spring Boot controller.

Explanation:

1. When you call /api/items?name=Table, the getItemByName method will be invoked with "Table" as the parameter value through @RequestParam.

2. When you call /api/items/Table, the getItemByPath method will be invoked with "Table" as the parameter value through @PathVariable.

5. When to use?

- Use @RequestParam when the parameter is optional, or you need to handle complex scenarios with default values or not strictly tied to a URI structure.

- Use @PathVariable for required parameters that are a natural part of the URI and when you're modeling RESTful endpoints.