Difference RequestParam and PathVariable

`@RequestParam`:

The `@RequestParam` annotation is used to extract query parameters from the URL of an HTTP request. It is commonly used to retrieve values from the query string or form data.

• Usage: Typically used for optional or default parameters in a URL. It is commonly used in form submissions or when data is passed in the query string of the URL.
• Scope: Works with query parameters, form data, and URL parameters.

`@PathVariable`:

The `@PathVariable` annotation is used to extract values from URI template variables. It is used when you want to capture values from the URL path.

• Usage: Typically used to extract values from the URL path that are part of the URI template. It is often used for RESTful services where resources are identified by path segments.
• Scope: Works with path segments in the URL.

1. Using `@RequestParam`

Example: Handling Query Parameters

UserController.java
```java
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
	
@RestController
public class UserController {

    @GetMapping("/user")
    public String getUser(@RequestParam(name = "id", defaultValue = "1") Long userId, 
                          @RequestParam(name = "name", required = false) String username) {
        return "User ID: " + userId + ", Username: " + username;
    }
}
```

Example URL: `/user?id=123&name=JohnDoe`

In this example:

• @RequestParam(name = "id", defaultValue = "1") extracts the query parameter id from the URL. If not provided, it defaults to 1.
• @RequestParam(name = "name", required = false) extracts the optional query parameter name from the URL.

2. Using `@PathVariable`
Example: Handling Path Variables

UserController.java
```java
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    @GetMapping("/user/{id}")
    public String getUserById(@PathVariable Long id) {
        return "User ID: " + id;
    }
}
```

Example URL: `/user/123`

In this example:

• @PathVariable Long id extracts the value of id from the URL path.

Summary of Differences RequestParam and PathVariable

• @RequestParam:
• Purpose: Extracts parameters from the query string or form data.
• Usage: Common for optional or default parameters.
• Example: /user?id=123&name=JohnDoe
• @PathVariable:
• Purpose: Extracts values from URI template variables in the path.
• Usage: Common for identifying resources in RESTful services.
• Example: /user/123

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