Implementing Feature Flag Management in Your Spring Boot Application Using API Calls and UI with Togglz

In modern software development, the ability to control features in a live application without deploying new code is crucial. This capability, known as feature flag management, allows teams to turn features on or off in real-time, enabling continuous delivery, A/B testing, and canary releases. It also plays a significant role in reducing risks associated with new deployments by controlling the exposure of new features to users.

In this article, we’ll walk through the process of implementing feature flag management in a Spring Boot application using Togglz. We’ll explore how to configure Togglz, define feature flags, and control their behaviour within your application.

1. Setting Up Togglz in Your Spring Boot Application

To get started with Togglz, you’ll need to add the necessary dependencies to your Spring Boot project. Open your build.gradle or pom.xml file and add the following dependencies:

implementation 'org.togglz:togglz-spring-boot-starter:3.1.2'
implementation 'org.togglz:togglz-console:3.3.3'

These dependencies include the core Togglz functionality and an optional web-based console for managing your feature flags.

2. Configuring Togglz

Next, you’ll need to configure Togglz in your Spring Boot application. This involves setting up a FeatureManager bean that Togglz uses to manage your feature flags.

Here’s how you can do it:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.togglz.core.manager.FeatureManager;
import org.togglz.core.manager.FeatureManagerBuilder;
import org.togglz.core.repository.jdbc.JdbcStateRepository;
import org.togglz.core.user.NoOpUserProvider;

import javax.sql.DataSource;

@Configuration
public class TogglzConfiguration {

    private final DataSource dataSource;

    @Autowired
    public TogglzConfiguration(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    @Bean
    public FeatureManager featureManager() {
        return new FeatureManagerBuilder()
                .featureEnum(ProductCheckFeature.class)
                .stateRepository(new JdbcStateRepository(dataSource))
                .userProvider(new NoOpUserProvider())
                .build();
    }
}

Explanation:

• DataSource: The DataSource is injected to be used by the JdbcStateRepository. This allows Togglz to persist feature flag states in a database.
• FeatureManager: The FeatureManager is built using a FeatureManagerBuilder. We specify the enum that defines the features (ProductCheckFeature.class), use a JdbcStateRepository for storing feature states, and a NoOpUserProvider since we’re not associating users with features in this example.

3. Defining Feature Flags with Enums

Togglz uses enums to define feature flags. Each constant in the enum represents a feature that can be toggled on or off. Here’s an example:

import org.togglz.core.Feature;
import org.togglz.core.annotation.Label;

public enum ProductCheckFeature implements Feature {

    @Label("product-check")
    PRODUCT_CHECK,

}

Explanation:

Label: The @Label annotation provides a human-readable name for the feature. This name will be displayed in the Togglz console if you decide to use it.

4. Using Feature Flags in Your Application

Once the feature flags are defined and the configuration is in place, you can start using them in your application. Here’s an example of how to check if a feature is active before executing certain code:

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.togglz.core.manager.FeatureManager;
import reactor.core.publisher.Mono;

import javax.servlet.http.HttpServletRequest;

@RestController
@RequestMapping("/api/products")
public class ProductController {

    private final FeatureManager featureManager;
    private final ProductService productService;

    public ProductController(FeatureManager featureManager, ProductService productService) {
        this.featureManager = featureManager;
        this.productService = productService;
    }

    @GetMapping("/check")
    public Mono<ResponseEntity<?>> checkProduct(@RequestParam String isbn, HttpServletRequest httpServletRequest) {
        if (featureManager.isActive(ProductCheckFeature.PRODUCT_CHECK)) {
            return productService
                    .productCheck(isbn, JwtUtils.getUserJwt(httpServletRequest), Boolean.FALSE)
                    .flatMap(response -> Mono.just(ResponseEntity.ok(response)));
        } 
        return Mono.just(ResponseEntity.status(HttpStatus.NOT_IMPLEMENTED).body("Feature is disabled"));
    }
}

Explanation:

• FeatureManager: The FeatureManager is injected into the controller and used to check if the PRODUCT_CHECK feature is active.
• Conditional Logic: If the feature is active, the product check operation is performed; otherwise, a “Feature is disabled” message is returned.

5. Managing Feature Flags via Togglz Console

The Togglz console is a powerful tool that allows you to manage your feature flags through a web interface. To enable the Togglz console, simply add the following property to your application.properties or application.yml file:

togglz.console.enabled=true

You can access the console by navigating to /togglz-console in your web browser. The console provides an easy-to-use interface for turning features on or off, changing their strategies, and viewing their current state.

Conclusion

Implementing feature flag management with Togglz in your Spring Boot application is a straightforward process that offers powerful control over your features. By following the steps outlined in this article, you can easily configure, define, and manage feature flags, allowing you to release new features with confidence and flexibility.

Whether you’re rolling out a new feature gradually, conducting A/B testing, or simply want to minimize deployment risks, Togglz provides a robust solution that integrates seamlessly into your Spring Boot application.

Happy Coding! 🚀