Java SDK

Get your Featureflow account at featureflow.io

GitHub: https://github.com/featureflow/featureflow-java-sdk

Installation

Add the dependency to your pom.xml:

<dependency>
    <groupId>io.featureflow</groupId>
    <artifactId>featureflow-java-sdk</artifactId>
    <version>1.2.1</version>
</dependency>

Or for Gradle, add to your build.gradle:

implementation 'io.featureflow:featureflow-java-sdk:1.2.1'

Quick Start

Create a Featureflow Client

Get your Server Environment API Key from the environment page in Featureflow and instantiate a singleton client:

String apiKey = "sdk-srv-env-YOUR_API_KEY";
FeatureflowClient featureflow = FeatureflowClient.builder(apiKey).build();

Singleton Pattern

The FeatureflowClient should be instantiated once and reused throughout your application. If using Spring, configure it as a @Bean in a @Configuration class.

Evaluate a Feature

Check the value of a feature flag in your code:

if (featureflow.evaluate("my-feature-key", user).isOn()) {
    // Feature is enabled
}

if (featureflow.evaluate("my-feature-key", user).isOff()) {
    // Feature is disabled
}

For custom variants beyond on/off:

if (featureflow.evaluate("my-feature-key", user).is("red")) {
    System.out.println("Variant: " + featureflow.evaluate("my-feature-key", user).value());
}

User Targeting

Pass user information to target features to specific users or segments:

FeatureflowUser user = new FeatureflowUser("unique-user-id")
    .withAttribute("tier", "silver")
    .withAttribute("age", 32)
    .withAttribute("signup_date", new DateTime(2017, 1, 1, 12, 0, 0, 0))
    .withAttribute("email", "user@example.com")
    .withAttributes("user_role", Arrays.asList("admin", "beta_tester"));

User attributes can be:

• String
• Number
• DateTime
• List<String>, List<Number>, or List<DateTime>

Evaluate with the user context:

featureflow.evaluate("my-feature", user).isOn();

note

When a list of attributes is passed, rules may match any value in the list. User attributes are stored in Featureflow for use in rule creation. Set .saveUser(false) on the user object to prevent this.

Spring Integration

Using a UserProvider

Create a FeatureflowUserProvider to automatically obtain the current user context (e.g., from a logged-in session):

@Configuration
public class FeatureflowConfig {

    @Autowired
    private UserService userService;

    @Bean
    public FeatureflowClient featureflowClient() {
        return FeatureflowClient.builder("sdk-srv-env-YOUR_API_KEY")
            .withUserProvider(() -> getFeatureflowUser())
            .build();
    }

    private FeatureflowUser getFeatureflowUser() {
        User currentUser = userService.getCurrentUser();
        return new FeatureflowUser(currentUser.getId())
            .withAttribute("name", currentUser.getName())
            .withAttributes("user_role", 
                currentUser.getRoles().stream()
                    .map(Role::getName)
                    .collect(Collectors.toList()));
    }
}

Using a UserLookupProvider

For user lookup by ID:

@Bean
public FeatureflowClient featureflowClient() {
    return FeatureflowClient.builder("sdk-srv-env-YOUR_API_KEY")
        .withUserLookupProvider(userId -> getFeatureflowUser(userId))
        .build();
}

private FeatureflowUser getFeatureflowUser(String userId) {
    User user = userService.findOneById(userId);
    return new FeatureflowUser(user.getId())
        .withAttribute("name", user.getName())
        .withAttributes("user_role", 
            user.getRoles().stream()
                .map(Role::getName)
                .collect(Collectors.toList()));
}

Then evaluate using just the user ID:

featureflow.evaluate("my-feature", "user123").isOn();

Real-time Updates

Listen for feature control updates using callbacks:

FeatureflowClient featureflow = FeatureflowClient.builder(apiKey)
    .withFeatures(Arrays.asList(
        new Feature("feature-one"),
        new Feature("feature-two")
    ))
    .withUpdateCallback(control -> 
        System.out.println("Feature updated: " + control.getKey()))
    .build();

API Reference

Evaluate Methods

Method	Description
evaluate(featureKey, user).isOn()	Returns true if variant equals "on"
evaluate(featureKey, user).isOff()	Returns true if variant equals "off"
evaluate(featureKey, user).is(value)	Returns true if variant equals the specified value
evaluate(featureKey, user).value()	Returns the current variant value as a string

FeatureflowUser Builder

Method	Description
withAttribute(key, value)	Add a single attribute (String, Number, or DateTime)
withAttributes(key, list)	Add a list attribute
saveUser(boolean)	Control whether user is saved in Featureflow (default: true)

Next Steps

• Gradual Rollouts — Release to a percentage of users
• Targeting Features — Control who sees what
• Managing Variants — Create custom feature states

License

Apache-2.0