How to Populate a Map<String, String> Using @RequestParam in Spring MVC

How can I populate a Map<String, String> with @RequestParam in Spring MVC?

@Controller
public class MyController {

    @GetMapping("/example")
    public String handleExample(@RequestParam Map<String, String> params) {
        // Access the populated params map here
        return "resultPage";
    }
}

In Spring MVC, the @RequestParam annotation is commonly used to extract query parameters from the URL into Java method parameters. When you want to collect all request parameters into a single map, you can use Map<String, String> as the parameter type. This allows you to handle dynamic parameter names efficiently, which is especially useful for APIs or forms with variable inputs.

@Controller
public class MyController {

    @GetMapping("/user")
    public String getUserInfo(@RequestParam Map<String, String> params) {
        // Log or process request params
        for (Map.Entry<String, String> entry : params.entrySet()) {
            System.out.println(entry.getKey() + " : " + entry.getValue());
        }
        return "userInfoPage";
    }
}

Causes

• Incorrect URL syntax when testing the endpoint.
• Forgetting to use the correct HTTP method (e.g., GET instead of POST).
• Mismatched parameter names in the request.

Solutions

• Ensure your HTTP request contains properly formatted query parameters.
• Test your endpoint using tools like Postman or cURL to verify the correct parameters are sent.
• Double-check your controller method annotations and parameter names for accuracy.

Mistake: Forgetting to add @RequestParam annotation

Solution: Always ensure you include @RequestParam before the Map parameter in the controller method.

Mistake: Using Map<Object, Object> instead of Map<String, String>

Solution: Use Map<String, String> to ensure type safety for the parameters.