What is the role of the @RequestParam annotation in Spring Boot?

Table of Contents

• Introduction
• Role of @RequestParam in Spring Boot
  • 1. Binding Request Parameters to Method Arguments
    • Example: Using @RequestParam in a Controller
    • Example Request:
  • 2. Specifying Default Values for Request Parameters
    • Example: Default Value for @RequestParam
    • Example Request:
  • 3. Handling Optional Parameters
    • Example: Optional @RequestParam
    • Example Request:
  • 4. Extracting Multiple Values for a Parameter
    • Example: Multiple Values for a Parameter
    • Example Request:
• Practical Example: Handling Query Parameters in a REST API
  • • Example: Filtering Products with @RequestParam
    • Example Request:
• Conclusion

Introduction

In Spring Boot, the @RequestParam annotation is used to extract query parameters from the URL of a request. It allows developers to handle dynamic data input from clients, such as form submissions or URL parameters, in a flexible and efficient manner. The annotation simplifies the process of extracting values from the request, providing an easy way to work with client input in a REST API or web controller.

Role of @RequestParam in Spring Boot

1. Binding Request Parameters to Method Arguments

The @RequestParam annotation binds query parameters from the URL to method parameters in a Spring controller. This enables the automatic extraction and conversion of data from the URL, making it easy to handle inputs in web applications.

Example: Using @RequestParam in a Controller

Example Request:

In this example, the category query parameter is extracted and passed to the getProductByCategory method, which processes the request.

2. Specifying Default Values for Request Parameters

You can specify default values for query parameters using the defaultValue attribute in @RequestParam. If a parameter is missing from the request, the default value is used instead.

Example: Default Value for @RequestParam

Example Request:

If no category parameter is provided in the URL, the method will use "all" as the default value for the category parameter.

3. Handling Optional Parameters

The @RequestParam annotation also allows you to mark parameters as optional by setting required = false. This is useful when a parameter may or may not be provided by the client.

Example: Optional @RequestParam

Example Request:

If the category parameter is not provided, the method defaults to fetching all products.

4. Extracting Multiple Values for a Parameter

@RequestParam can handle multiple values for the same parameter by specifying the List or Set collection type.

Example: Multiple Values for a Parameter

Example Request:

This request would bind the categories parameter to a list containing ["electronics", "clothing"].

Practical Example: Handling Query Parameters in a REST API

Consider a scenario where you need to filter products based on their category and price range in a Spring Boot application.

Example: Filtering Products with @RequestParam

Example Request:

In this example, the category, minPrice, and maxPrice parameters are used to filter the products returned by the service.

Conclusion

The @RequestParam annotation in Spring Boot plays a crucial role in extracting and processing query parameters in REST APIs. By using @RequestParam, developers can easily handle input data from clients, specify default values, and make parameters optional. This flexibility allows for more dynamic and responsive API design, making it easier to work with various client-side requests and parameters.