Getting Started with Spring Boot Request Interceptor: A Step-by-Step Tutorial

Introduction:
In this tutorial, we’ll delve into the world of Spring Boot request interceptors, exploring what they are, why they’re useful, and how to implement them in your applications. Request interceptors provide a mechanism to intercept and potentially modify HTTP requests and responses before they reach the controller layer. Let’s dive in!

Prerequisites:
Before we begin, make sure you have:

1. Basic knowledge of Spring Boot and Spring MVC.
2. JDK installed on your system.
3. An Integrated Development Environment (IDE) such as IntelliJ IDEA or Eclipse.

1. What is a Request Interceptor?
A request interceptor in Spring Boot is a component that intercepts incoming HTTP requests before they are processed by the controller. It allows you to perform pre-processing tasks, such as logging, authentication, validation, or modifying the request/response, before passing it to the controller.

2. Creating a Request Interceptor:
To create a request interceptor in Spring Boot, follow these steps:

Step 1: Create a class that implements the HandlerInterceptor interface.

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CustomInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // Logic to execute before the request is handled by the controller
        return true; // Return true to proceed with the handler execution, false otherwise
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        // Logic to execute after the controller method is invoked, but before the view is rendered
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        // Logic to execute after the request has been processed, both controller and view rendering are done
    }
}

Step 2: Register the interceptor in your Spring Boot application.

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new CustomInterceptor()).addPathPatterns("/**");
    }
}

3. Using the Request Interceptor:
Now that we have created and registered our interceptor, it will be invoked for every incoming request. You can customize the interceptor’s behavior by implementing the preHandle, postHandle, and afterCompletion methods as per your requirements.

Example Use Cases:

• Logging incoming requests.
• Authentication and authorization.
• Request/response modification.
• Adding custom headers.

Conclusion:
In this tutorial, we explored the concept of request interceptors in Spring Boot and learned how to create and use them in our applications. Interceptors provide a powerful mechanism to intercept and modify HTTP requests and responses, allowing you to implement cross-cutting concerns effectively. Experiment with different use cases to leverage the full potential of request interceptors in your Spring Boot projects. Happy coding!