Java SDK - GrowthBook Documentation

This supports Java applications using Java version 1.8 and higher.

Installation

Gradle

To install in a Gradle project, add Jitpack to your repositories, and then add the dependency with the latest version to your project’s dependencies.

allprojects {
    repositories {
        maven { url 'https://jitpack.io' }
    }
}

dependencies {
    implementation 'com.github.growthbook:growthbook-sdk-java:0.5.0'
}

repositories {
    maven {
        setUrl("https://jitpack.io")
    }
}

dependencies {
    implementation("com.github.growthbook:growthbook-sdk-java:0.5.0")
}

Maven

To install in a Maven project, add Jitpack to your repositories:

<repositories>
    <repository>
        <id>jitpack.io</id>
        <url>https://jitpack.io</url>
    </repository>
</repositories>

Next, add the dependency with the latest version to your project’s dependencies:

<dependency>
    <groupId>com.github.growthbook</groupId>
    <artifactId>growthbook-sdk-java</artifactId>
    <version>0.5.0</version>
</dependency>

Usage

There are two main approaches to using the GrowthBook Java SDK:

Enhanced Client (Recommended) - For better performance with multi-context support
Traditional per-request approach - Create a new context and SDK instance per request

Enhanced Client (Recommended)

Available starting in version 0.9.0 For improved performance and better resource management, especially in web applications, use the enhanced client pattern. This approach allows you to reuse a single client instance across multiple requests while providing different user contexts for each evaluation while calling the feature methods like isOn(). This GrowthBookClient instance is decoupled from the GBContext, creates a singleton featureRepository based on your refreshStrategy and uses the latest features at the time of evaluation, all managed internally.

Basic Enhanced Client Usage

// build options to configure your Growthbook instance
Options options = Options.builder()
        .apiHost("https://cdn.growthbook.io")
        .clientKey("sdk-abc123")
        .build();

// Create growthbook instance using the options you need
GrowthBookClient gb = new GrowthBookClient(options);

// call the init method to load features
gb.initialize();

gb.isOn("featureKey", UserContext.builder()
    .attributesJson("{\"id\" : \"123\"}").build()
);

Using the Enhanced Client with Different User Contexts

// build options to configure your Growthbook instance
Options options = Options.builder()
        .apiHost("https://cdn.growthbook.io")
        .clientKey("sdk-abc123")
        .build();

// Create growthbook instance using the options you need
GrowthBookClient gb = new GrowthBookClient(options);

// call the init method to load features
gb.initialize();

// Use the same client instance with different user contexts
// User 1 context
UserContext user1Context = UserContext.builder()
    .attributesJson("{\"id\":\"user_123\",\"country\":\"US\",\"premium\":true}")
    .build();

boolean showNewFeature = gb.isOn("new-homepage", user1Context);
String buttonColor = gb.getFeatureValue("button-color", "blue", user1Context);

// User 2 context - same client, different context
UserContext user2Context = UserContext.builder()
    .attributesJson("{\"id\":\"user_456\",\"country\":\"CA\",\"premium\":false}")
    .build();

boolean showFeatureForUser2 = gb.isOn("new-homepage", user2Context);
String colorForUser2 = gb.getFeatureValue("button-color", "blue", user2Context);

Thread Safety Note

While the enhanced client is designed for concurrent use, full concurrency support is still being refined. For high-concurrency applications, consider:

Using connection pooling for database-backed sticky bucket services
Implementing proper synchronization for custom tracking callbacks
Testing thoroughly under expected load conditions

Traditional Usage

For new projects, we recommend using the Enhanced Client instead for better performance. There are 2 steps to initializing the traditional GrowthBook SDK:

Create a GrowthBook context GBContext with the features JSON and the user attributes
Create the GrowthBook SDK class with the context

GrowthBook context

The GrowthBook context GBContext can be created either by implementing the builder class, available at GBContext.builder(), or by using the GBContext constructor.

Field name	Type	Description
`attributesJson`	`String`	The user attributes JSON. See Attributes.
`featuresJson`	`String`	The features JSON served by the GrowthBook API (or equivalent). See Features.
`enabled`	`Boolean`	Whether to enable the functionality of the SDK (default: `true`)
`isQaMode`	`Boolean`	Whether the SDK is in QA mode. Not for production use. If true, random assignment is disabled and only explicitly forced variations are used (default: `false`)
`url`	`String`	The URL of the current page. Useful when evaluating features and experiments based on the page URL.
`forcedVariationsMap`	`Map<String, Integer>`	Force specific experiments to always assign a specific variation (used for QA)
`trackingCallback`	`TrackingCallback`	A callback that will be invoked with every experiment evaluation where the user is included in the experiment. See TrackingCallback. To subscribe to all evaluated events regardless of whether the user is in the experiment, see Subscribing to experiment runs.
`featureUsageCallback`	`FeatureUsageCallback`	A callback that will be invoked every time a feature is viewed. See FeatureUsageCallback

Using the GBContext builder

The builder is the easiest to use way to construct a GBContext, allowing you to provide as many or few arguments as you’d like. All fields mentioned above are available via the builder.

// Fetch feature definitions from the GrowthBook API
// We recommend adding a caching layer in production
// Get your endpoint in the Environments tab -> SDK Endpoints: https://app.growthbook.io/environments
URI featuresEndpoint = new URI("https://cdn.growthbook.io/api/features/<environment_key>");
HttpRequest request = HttpRequest.newBuilder().uri(featuresEndpoint).GET().build();
HttpResponse<String> response = HttpClient.newBuilder().build()
    .send(request, HttpResponse.BodyHandlers.ofString());
String featuresJson = new JSONObject(response.body()).get("features").toString();

// JSON serializable user attributes
String userAttributesJson = user.toJson();

// Initialize the GrowthBook SDK with the GBContext
GBContext context = GBContext
    .builder()
    .featuresJson(featuresJson)
    .attributesJson(userAttributesJson)
    .build();

GrowthBook growthBook = new GrowthBook(context);

// Fetch feature definitions from the GrowthBook API
// We recommend adding a caching layer in production
// Get your endpoint in the Environments tab -> SDK Endpoints: https://app.growthbook.io/environments
val featuresEndpoint = URI.create("https://cdn.growthbook.io/api/features/<environment_key>")
val request = HttpRequest.newBuilder().uri(featuresEndpoint).GET().build();
val response = HttpClient.newBuilder().build()
    .send(request, HttpResponse.BodyHandlers.ofString());
val featuresJson = JSONObject(response.body()).get("features").toString()

// JSON serializable user attributes
val userAttributes = """
    {
        "id": "user-abc123",
        "country": "canada"
    }
""".trimIndent()

// Initialize the GrowthBook SDK with the GBContext
val context = GBContext
    .builder()
    .featuresJson(featuresJson)
    .attributesJson(userAttributes)
    .build()

val growthBook = GrowthBook(context)

HttpClient recommendationThe above example uses java.net.http.HttpClient which, depending on your web framework, may not be the best option, in which case it is recommended to use a networking library more suitable for your implementation.

Using the GBContext constructor

You can also use GBContext constructor if you prefer, which will require you to pass all arguments explicitly.

// Fetch feature definitions from the GrowthBook API
// We recommend adding a caching layer in production
// Get your endpoint in the Environments tab -> SDK Endpoints: https://app.growthbook.io/environments
URI featuresEndpoint = new URI("https://cdn.growthbook.io/api/features/<environment_key>");
HttpRequest request = HttpRequest.newBuilder().uri(featuresEndpoint).GET().build();
HttpResponse<String> response = HttpClient.newBuilder().build()
    .send(request, HttpResponse.BodyHandlers.ofString());
String featuresJson = new JSONObject(response.body()).get("features").toString();

// JSON serializable user attributes
String userAttributesJson = user.toJson();

boolean isEnabled = true;
boolean isQaMode = false;
String url = null;
Map<String, Integer> forcedVariations = new HashMap<>();
TrackingCallback trackingCallback = new TrackingCallback() {
    @Override
    public <ValueType> void onTrack(Experiment<ValueType> experiment, ExperimentResult<ValueType> experimentResult) {
        // TODO: Something after it's been tracked
    }
};

// Initialize the GrowthBook SDK with the GBContext
GBContext context = new GBContext(
    userAttributesJson,
    featuresJson,
    isEnabled,
    isQaMode,
    url,
    forcedVariations,
    trackingCallback
);

GrowthBook growthBook = new GrowthBook(context);

// Fetch feature definitions from the GrowthBook API
// We recommend adding a caching layer in production
// Get your endpoint in the Environments tab -> SDK Endpoints: https://app.growthbook.io/environments
val featuresEndpoint = URI.create("https://cdn.growthbook.io/api/features/<environment_key>")
val request = HttpRequest.newBuilder().uri(featuresEndpoint).GET().build();
val response = HttpClient.newBuilder().build()
    .send(request, HttpResponse.BodyHandlers.ofString());
val featuresJson = JSONObject(response.body()).get("features").toString()

// JSON serializable user attributes
val userAttributes = """
    {
        "id": "user-abc123",
        "country": "canada"
    }
""".trimIndent()

val isEnabled = true
val isQaMode = false
val url: String? = null
val forcedVariations = mapOf<String, Int>()
val trackingCallback: TrackingCallback = object : TrackingCallback {
    override fun <ValueType : Any?> onTrack(
        experiment: Experiment<ValueType>?,
        experimentResult: ExperimentResult<ValueType>?
    ) {
        // TODO: Something after it's been tracked
    }
}

// Initialize the GrowthBook SDK with the GBContext
val context = GBContext(
    userAttributes,
    featuresJson,
    isEnabled,
    isQaMode,
    url,
    forcedVariations,
    trackingCallback
)

val growthBook = GrowthBook(context)

For complete examples, see the Examples section below.

Features

The features JSON is equivalent to the features property that is returned from the SDK Connection endpoint.

You can read more about features here
You can see an example features JSON here

Attributes

Attributes are a JSON string. You can specify attributes about the current user and request. Here’s an example:

String userAttributes = "{\"country\": \"canada\", \"id\": \"user-abc123\"}";

val userAttributes = """
    {
        "id": "user-abc123",
        "country": "canada"
    }
""".trimIndent()

If you need to set or update attributes asynchronously, you can do so with Context#attributesJson or GrowthBook#setAttributes. This will completely overwrite the attributes object with whatever you pass in. Also, be aware that changing attributes may change the assigned feature values. This can be disorienting to users if not handled carefully.

Secure Attributes

When secure attribute hashing is enabled, all targeting conditions in the SDK payload referencing attributes with datatype secureString or secureString[] will be anonymized via SHA-256 hashing. This allows you to safely target users based on sensitive attributes. You must enable this feature in your SDK Connection for it to take effect. If your SDK Connection has secure attribute hashing enabled, you will need to manually hash any secureString or secureString[] attributes that you pass into the GrowthBook SDK. To hash an attribute, use a cryptographic library with SHA-256 support, and compute the SHA-256 hashed value of your attribute plus your organization’s secure attribute salt.

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Base64;

// Your secure attribute salt (set in Organization Settings)
String salt = "f09jq3fij";

// Create and initialize the enhanced client once
Options options = Options.builder()
        .apiHost("https://cdn.growthbook.io")
        .clientKey("sdk-abc123")
        .build();

GrowthBookClient gb = new GrowthBookClient(options);
gb.initialize();

// Helper method to hash secure attributes
private String hashSecureAttribute(String value, String salt) {
    try {
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        byte[] hash = digest.digest((salt + value).getBytes(StandardCharsets.UTF_8));
        return Base64.getEncoder().encodeToString(hash);
    } catch (NoSuchAlgorithmException e) {
        throw new RuntimeException("SHA-256 not available", e);
    }
}

// Hash secure attributes for each user evaluation
String userEmail = user.getEmail();
String hashedEmail = hashSecureAttribute(userEmail, salt);

List<String> userTags = user.getTags();
List<String> hashedTags = userTags.stream()
    .map(tag -> hashSecureAttribute(tag, salt))
    .collect(Collectors.toList());

// Create user context with hashed attributes
UserContext userContext = UserContext.builder()
    .attributesJson(String.format(
        "{\"id\":\"%s\",\"loggedIn\":true,\"email\":\"%s\",\"tags\":%s}",
        user.getId(),
        hashedEmail,
        new Gson().toJson(hashedTags)
    ))
    .build();

// Use the enhanced client with hashed attributes
boolean hasFeature = gb.isOn("premium-feature", userContext);
String theme = gb.getFeatureValue("theme", "light", userContext);

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Base64;

// Your secure attribute salt (set in Organization Settings)
String salt = "f09jq3fij";

// Hashing a secureString attribute
String userEmail = user.getEmail();
String hashedEmail = "";

try {
    MessageDigest digest = MessageDigest.getInstance("SHA-256");
    byte[] hash = digest.digest((salt + userEmail).getBytes(StandardCharsets.UTF_8));
    hashedEmail = Base64.getEncoder().encodeToString(hash);
} catch (NoSuchAlgorithmException e) {
    // Handle exception
}

// Hashing a secureString[] attribute
List<String> userTags = user.getTags();
List<String> hashedTags = new ArrayList<>();

try {
    MessageDigest digest = MessageDigest.getInstance("SHA-256");
    for (String tag : userTags) {
        byte[] hash = digest.digest((salt + tag).getBytes(StandardCharsets.UTF_8));
        hashedTags.add(Base64.getEncoder().encodeToString(hash));
    }
} catch (NoSuchAlgorithmException e) {
    // Handle exception
}

// Create attributes JSON with hashed values
String attributesJson = String.format(
    "{\"id\":\"%s\",\"loggedIn\":true,\"email\":\"%s\",\"tags\":%s}",
    user.getId(),
    hashedEmail,
    Arrays.toString(hashedTags.toArray())
);

// Use the hashed attributes when creating your GrowthBook instance
GBContext context = GBContext
    .builder()
    .featuresJson(featuresJson)
    .attributesJson(attributesJson)
    .build();

GrowthBook growthBook = new GrowthBook(context);

Using Features

Every feature has a “value” which is assigned to a user. This value can be any JSON data type. If a feature doesn’t exist, the value will be null. There are 4 main methods for evaluating features.

Method	Return type	Description
`isOn(String)`	`Boolean`	Returns true if the value is a truthy value
`isOff(String)`	`Boolean`	Returns true if the value is a falsy value
`getFeatureValue(String)`	generic `T` (nullable)	Returns the value cast to the generic type. Type is inferred based on the `defaultValue` argument provided.
`evalFeature(String)`	`FeatureResult<T>`	Returns a feature result with a value of generic type `T`. The value type needs to be specified in the generic parameter.

// Create enhanced client
Options options = Options.builder()
        .apiHost("https://cdn.growthbook.io")
        .clientKey("sdk-abc123")
        .build();

GrowthBookClient gb = new GrowthBookClient(options);
gb.initialize();

// Create user context for evaluations
UserContext userContext = UserContext.builder()
    .attributesJson("{\"id\":\"user_123\",\"premium\":true}")
    .build();

// Boolean feature checks
if (gb.isOn("dark_mode", userContext)) {
    // value is truthy
}

if (gb.isOff("dark_mode", userContext)) {
    // value is falsy
}

// Get feature values with defaults
Float donutPrice = gb.getFeatureValue("donut_price", 5.0f, userContext);
String theme = gb.getFeatureValue("theme", "light", userContext);
Integer maxItems = gb.getFeatureValue("max_items", 10, userContext);

// Get detailed feature result
FeatureResult<Float> priceResult = gb.evalFeature("donut_price", userContext);
Float price = priceResult.getValue();
String source = priceResult.getSource().toString();

// Create traditional client
GBContext context = GBContext
    .builder()
    .featuresJson(featuresJson)
    .attributesJson("{\"id\":\"user_123\",\"premium\":true}")
    .build();

GrowthBook growthBook = new GrowthBook(context);

// Boolean feature checks
if (growthBook.isOn("dark_mode")) {
    // value is truthy
}

if (growthBook.isOff("dark_mode")) {
    // value is falsy
}

// Get feature values with defaults
Float donutPrice = growthBook.getFeatureValue("donut_price", 5.0f);
String theme = growthBook.getFeatureValue("theme", "light");
Integer maxItems = growthBook.getFeatureValue("max_items", 10);

// Get detailed feature result
FeatureResult<Float> priceResult = growthBook.<Float>evalFeature("donut_price");
Float price = priceResult.getValue();
String source = priceResult.getSource().toString();

isOn() / isOff()

These methods return a boolean for truthy and falsy values. Only the following values are considered to be “falsy”:

null
false
""
0

Everything else is considered “truthy”, including empty arrays and objects. If the value is “truthy”, then isOn() will return true and isOff() will return false. If the value is “falsy”, then the opposite values will be returned.

getFeatureValue(featureKey, defaultValue)

This method has a variety of overloads to help with casting values to primitive and complex types. In short, the type of the defaultValue argument will determine the return type of the function.

Return type	Method	Additional Info
`Boolean`	`getFeatureValue(String featureKey, Boolean defaultValue)`
`Double`	`getFeatureValue(String featureKey, Double defaultValue)`
`Float`	`getFeatureValue(String featureKey, Float defaultValue)`
`Integer`	`getFeatureValue(String featureKey, Integer defaultValue)`
`String`	`getFeatureValue(String featureKey, String defaultValue)`
`<ValueType> ValueType`	`getFeatureValue(String featureKey, ValueType defaultValue, Class<ValueType> gsonDeserializableClass)`	Internally, the SDK uses Gson. You can pass any class that does not require a custom deserializer.
`Object`	`getFeatureValue(String featureKey, Object defaultValue)`	Use this method if you need to cast a complex object that uses a custom deserializer, or if you use a different JSON serialization library than Gson, and cast the type yourself.

See the Java Docs for more information. See the unit tests for example implementations including type casting for all above-mentioned methods.

evalFeature(String)

The evalFeature method returns a FeatureResult<T> object with more info about why the feature was assigned to the user. The T type corresponds to the value type of the feature. In the above example, T is Float. FeatureResult<T> It has the following getters.

Method	Return type	Description
`getValue()`	generic `T` (nullable)	The evaluated value of the feature
`getSource()`	`enum FeatureResultSource` (nullable)	The reason/source for the evaluated feature value.
`getRuleId()`	`String` (nullable)	ID of the rule that was used to assign the value to the user.
`getExperiment()`	`Experiment<T>` (nullable)	The experiment details, available only if the feature evaluates due to an experiment.
`getExperimentResult()`	`ExperimentResult<T>` (nullable)	The experiment result details, available only if the feature evaluates due to an experiment.

As expected in Kotlin, you can access these getters using property accessors.

Inline Experiments

Instead of declaring all features up-front in the context and referencing them by IDs in your code, you can also just run an experiment directly. This is done with the growthbook.run(Experiment<T>) method.

// Create enhanced client
Options options = Options.builder()
        .apiHost("https://cdn.growthbook.io")
        .clientKey("sdk-abc123")
        .build();

GrowthBookClient gb = new GrowthBookClient(options);
gb.initialize();

// Create user context
UserContext userContext = UserContext.builder()
    .attributesJson("{\"id\":\"user_123\",\"employee\":true}")
    .build();

// Create and run inline experiment
Experiment<Float> donutPriceExperiment = Experiment
    .<Float>builder()
    .key("donut-price-test")
    .variations(Arrays.asList(2.50f, 3.00f, 3.50f))
    .weights(Arrays.asList(0.33f, 0.33f, 0.34f))
    .conditionJson("{\"employee\": true}")
    .build();

ExperimentResult<Float> result = gb.run(donutPriceExperiment, userContext);
Float donutPrice = result.getValue();

// Check if user was included in experiment
if (result.getInExperiment()) {
    System.out.println("User is in experiment, variation: " + result.getVariationId());
    System.out.println("Donut price: $" + donutPrice);
} else {
    System.out.println("User not in experiment");
}

// String experiment example
Experiment<String> buttonColorExperiment = Experiment
    .<String>builder()
    .key("button-color")
    .variations(Arrays.asList("blue", "red", "green"))
    .build();

ExperimentResult<String> colorResult = gb.run(buttonColorExperiment, userContext);
String buttonColor = colorResult.getValue();

// Create traditional client
GBContext context = GBContext
    .builder()
    .featuresJson(featuresJson)
    .attributesJson("{\"id\":\"user_123\",\"employee\":true}")
    .build();

GrowthBook growthBook = new GrowthBook(context);

// Create and run inline experiment
Experiment<Float> donutPriceExperiment = Experiment
    .<Float>builder()
    .key("donut-price-test")
    .variations(Arrays.asList(2.50f, 3.00f, 3.50f))
    .weights(Arrays.asList(0.33f, 0.33f, 0.34f))
    .conditionJson("{\"employee\": true}")
    .build();

ExperimentResult<Float> result = growthBook.run(donutPriceExperiment);
Float donutPrice = result.getValue();

// Check if user was included in experiment
if (result.getInExperiment()) {
    System.out.println("User is in experiment, variation: " + result.getVariationId());
    System.out.println("Donut price: $" + donutPrice);
} else {
    System.out.println("User not in experiment");
}

// String experiment example
Experiment<String> buttonColorExperiment = Experiment
    .<String>builder()
    .key("button-color")
    .variations(Arrays.asList("blue", "red", "green"))
    .build();

ExperimentResult<String> colorResult = growthBook.run(buttonColorExperiment);
String buttonColor = colorResult.getValue();

Inline experiment return value ExperimentResult

An ExperimentResult<T> is returned where T is the generic value type for the experiment. There’s also a number of methods available.

Method	Return type	Description
`getValue()`	generic `T` (nullable)	The evaluated value of the feature
`getVariationId()`	`Integer` (nullable)	Index of the variation used, if applicable
`getInExperiment()`	`Boolean`	If the user was in the experiment. This will be false if the user was excluded from being part of the experiment for any reason (e.g. failed targeting conditions).
`getHashAttribute()`	`String`	User attribute used for hashing, defaulting to `id` if not set.
`getHashValue()`	`String` (nullable)	The hash value used for evaluating the experiment, if applicable.
`getFeatureId()`	`String`	The feature key/ID
`getHashUsed()`	`Boolean`	If a hash was used to evaluate the experiment. This flag will only be true if the user was randomly assigned a variation. If the user was forced into a specific variation instead, this flag will be false.

As expected in Kotlin, you can access these getters using property accessors.

Tracking feature usage and experiment impressions

This section covers how to track and monitor feature usage and experiment impressions in your application. There are several types of callbacks and events you can subscribe to:

Tracking Callback - Called when a user is included in an experiment
Feature Usage Callback - Called every time a feature is evaluated
Experiment Run Callback - Called for every experiment evaluation (regardless of inclusion)

Tracking Callback

Any time an experiment is run to determine the value of a feature, we may call this callback so you can record the assigned value in your event tracking or analytics system of choice. The tracking callback is only called when the user is in the experiment. If they are not in the experiment, this will not be called.

// Create tracking callback
TrackingCallback trackingCallback = new TrackingCallback() {
    @Override
    public <ValueType> void onTrack(
        Experiment<ValueType> experiment,
        ExperimentResult<ValueType> experimentResult
    ) {
        // Send to your analytics system
        analytics.track("experiment_viewed", Map.of(
            "experiment_id", experiment.getKey(),
            "variation_id", experimentResult.getVariationId(),
            "user_id", experimentResult.getHashAttribute()
        ));
    }
};

// Create enhanced client with tracking
Options options = Options.builder()
        .apiHost("https://cdn.growthbook.io")
        .clientKey("sdk-abc123")
        .trackingCallback(trackingCallback)
        .build();

GrowthBookClient gb = new GrowthBookClient(options);
gb.initialize();

// Use features - tracking callback will be called automatically when user is in experiment
UserContext userContext = UserContext.builder()
    .attributesJson("{\"id\":\"user_123\",\"employee\":true}")
    .build();

boolean newFeature = gb.isOn("new-checkout-flow", userContext);

// Create tracking callback
TrackingCallback trackingCallback = new TrackingCallback() {
    @Override
    public <ValueType> void onTrack(
        Experiment<ValueType> experiment,
        ExperimentResult<ValueType> experimentResult
    ) {
        // Send to your analytics system
        System.out.println("Experiment tracked: " + experiment.getKey());
        System.out.println("Variation: " + experimentResult.getVariationId());
    }
};

// Create context with tracking callback
GBContext context = GBContext
    .builder()
    .featuresJson(featuresJson)
    .attributesJson(userAttributesJson)
    .trackingCallback(trackingCallback)
    .build();

GrowthBook growthBook = new GrowthBook(context);

// Use features - tracking callback will be called when user is in experiment
boolean newFeature = growthBook.isOn("new-checkout-flow");

Feature Usage Callback

Any time a feature is evaluated (regardless of experiment participation), this callback is called with the feature key and result.

// Create feature usage callback
FeatureUsageCallback featureUsageCallback = new FeatureUsageCallback() {
    @Override
    public <ValueType> void onFeatureUsage(
        String featureKey,
        FeatureResult<ValueType> featureResult
    ) {
        // Log feature usage
        logger.info("Feature '{}' evaluated with value: {}",
                   featureKey, featureResult.getValue());

        // Send to analytics
        analytics.track("feature_used", Map.of(
            "feature_key", featureKey,
            "feature_value", featureResult.getValue(),
            "source", featureResult.getSource().toString()
        ));
    }
};

// Create enhanced client with feature usage tracking
Options options = Options.builder()
        .apiHost("https://cdn.growthbook.io")
        .clientKey("sdk-abc123")
        .featureUsageCallback(featureUsageCallback)
        .build();

GrowthBookClient gb = new GrowthBookClient(options);
gb.initialize();

// Feature usage callback will be called for every feature evaluation
UserContext userContext = UserContext.builder()
    .attributesJson("{\"id\":\"user_123\"}")
    .build();

String theme = gb.getFeatureValue("theme", "light", userContext);
boolean darkMode = gb.isOn("dark_mode", userContext);

// Create feature usage callback
FeatureUsageCallback featureUsageCallback = new FeatureUsageCallback() {
    @Override
    public <ValueType> void onFeatureUsage(
        String featureKey,
        FeatureResult<ValueType> featureResult
    ) {
        // Log feature usage
        System.out.println("Feature used: " + featureKey +
                          " = " + featureResult.getValue());
    }
};

// Create context with feature usage callback
GBContext context = GBContext
    .builder()
    .featuresJson(featuresJson)
    .attributesJson(userAttributesJson)
    .featureUsageCallback(featureUsageCallback)
    .build();

GrowthBook growthBook = new GrowthBook(context);

// Feature usage callback will be called for every feature evaluation
String theme = growthBook.getFeatureValue("theme", "light");
boolean darkMode = growthBook.isOn("dark_mode");

Experiment Run Callback

You can subscribe to experiment run evaluations using the ExperimentRunCallback. This callback is called for every experiment evaluation, regardless of whether the user is included in the experiment.

// Create experiment run callback
ExperimentRunCallback experimentRunCallback = new ExperimentRunCallback() {
    @Override
    public <ValueType> void onExperimentRun(
        Experiment<ValueType> experiment,
        ExperimentResult<ValueType> experimentResult
    ) {
        // Track all experiment evaluations (included and excluded users)
        analytics.track("experiment_evaluated", Map.of(
            "experiment_id", experiment.getKey(),
            "user_in_experiment", experimentResult.getInExperiment(),
            "variation_id", experimentResult.getVariationId(),
            "hash_used", experimentResult.getHashUsed()
        ));
    }
};

// Enhanced client doesn't directly support ExperimentRunCallback
// Use inline experiments with the callback
Options options = Options.builder()
        .apiHost("https://cdn.growthbook.io")
        .clientKey("sdk-abc123")
        .build();

GrowthBookClient gb = new GrowthBookClient(options);
gb.initialize();

// Subscribe to experiment runs (you can subscribe multiple callbacks)
gb.subscribe(experimentRunCallback);

// Run inline experiments - callback will be triggered
UserContext userContext = UserContext.builder()
    .attributesJson("{\"id\":\"user_123\",\"employee\":true}")
    .build();

Experiment<String> buttonColorExperiment = Experiment
    .<String>builder()
    .key("button-color")
    .variations(Arrays.asList("blue", "red", "green"))
    .build();

ExperimentResult<String> result = gb.run(buttonColorExperiment, userContext);

// Create experiment run callback
ExperimentRunCallback experimentRunCallback = new ExperimentRunCallback() {
    @Override
    public <ValueType> void onExperimentRun(
        Experiment<ValueType> experiment,
        ExperimentResult<ValueType> experimentResult
    ) {
        // Track all experiment evaluations
        System.out.println("Experiment evaluated: " + experiment.getKey());
        System.out.println("User in experiment: " + experimentResult.getInExperiment());
    }
};

// Create GrowthBook instance
GBContext context = GBContext
    .builder()
    .featuresJson(featuresJson)
    .attributesJson(userAttributesJson)
    .build();

GrowthBook growthBook = new GrowthBook(context);

// Subscribe to experiment runs (you can subscribe multiple callbacks)
growthBook.subscribe(experimentRunCallback);

// Run inline experiments - callback will be triggered
Experiment<String> buttonColorExperiment = Experiment
    .<String>builder()
    .key("button-color")
    .variations(Arrays.asList("blue", "red", "green"))
    .build();

ExperimentResult<String> result = growthBook.run(buttonColorExperiment);

Multiple Callback Subscriptions

You can subscribe to multiple experiment run callbacks:

// Multiple callbacks for different purposes
ExperimentRunCallback analyticsCallback = (experiment, result) -> {
    // Send to analytics
    analytics.track("experiment_run", Map.of(
        "experiment", experiment.getKey(),
        "included", result.getInExperiment()
    ));
};

ExperimentRunCallback loggingCallback = (experiment, result) -> {
    // Log for debugging
    logger.debug("Experiment {} evaluated for user {}",
                experiment.getKey(), result.getHashAttribute());
};

// Subscribe multiple callbacks
gb.subscribe(analyticsCallback);
gb.subscribe(loggingCallback);

// Multiple callbacks for different purposes
ExperimentRunCallback analyticsCallback = (experiment, result) -> {
    // Send to analytics
    System.out.println("Analytics: " + experiment.getKey());
};

ExperimentRunCallback loggingCallback = (experiment, result) -> {
    // Log for debugging
    System.out.println("Debug: " + experiment.getKey());
};

// Subscribe multiple callbacks
growthBook.subscribe(analyticsCallback);
growthBook.subscribe(loggingCallback);

Working with Encrypted features

As of version 0.3.0, the Java SDK supports decrypting encrypted features. You can learn more about SDK Connection Endpoint Encryption. The main difference is you create a GBContext by passing an encryption key (.encryptionKey() when using the builder) and using the encrypted payload as the features JSON (.featuresJson() for the builder).

// Fetch feature definitions from the GrowthBook API
// We recommend adding a caching layer in production
// Get your endpoint in the Environments tab -> SDK Endpoints: https://app.growthbook.io/environments
URI featuresEndpoint = new URI("https://cdn.growthbook.io/api/features/<environment_key>");
HttpRequest request = HttpRequest.newBuilder().uri(featuresEndpoint).GET().build();
HttpResponse<String> response = HttpClient.newBuilder().build()
    .send(request, HttpResponse.BodyHandlers.ofString());
String encryptedFeaturesJson = new JSONObject(response.body()).get("encryptedFeatures").toString();

// JSON serializable user attributes
String userAttributesJson = user.toJson();

// You can store your encryption key as an environment variable rather than hardcoding in plain text in your codebase
String encryptionKey = "<key-for-decrypting>";

// Initialize the GrowthBook SDK with the GBContext and the encryption key
GBContext context = GBContext
.builder()
.featuresJson(encryptedFeaturesJson)
.encryptionKey(encryptionKey)
.attributesJson(userAttributesJson)
.build();

GrowthBook growthBook = new GrowthBook(context);

// Fetch feature definitions from the GrowthBook API
// We recommend adding a caching layer in production
// Get your endpoint in the Environments tab -> SDK Endpoints: https://app.growthbook.io/environments
val featuresEndpoint = URI.create("https://cdn.growthbook.io/api/features/<environment_key>")
val request = HttpRequest.newBuilder().uri(featuresEndpoint).GET().build();
val response = HttpClient.newBuilder().build()
    .send(request, HttpResponse.BodyHandlers.ofString());
val encryptedFeaturesJson = JSONObject(response.body()).get("encryptedFeatures").toString()

// JSON serializable user attributes
val userAttributes = """
    {
        "id": "user-abc123",
        "country": "canada"
    }
""".trimIndent()

// You can store your encryption key as an environment variable rather than hardcoding in plain text in your codebase
val encryptionKey = "<key-for-decrypting>";

// Initialize the GrowthBook SDK with the GBContext and the encryption key
val context = GBContext
    .builder()
    .featuresJson(encryptedFeaturesJson)
    .encryptionKey(encryptionKey)
    .attributesJson(userAttributes)
    .build()

val growthBook = GrowthBook(context)

Fetching, Caching, and Refreshing features with GBFeaturesRepository

As of version 0.4.0, the Java SDK provides an optional GBFeaturesRepository class which will manage networking for you in the following ways:

Fetching features from the SDK endpoint when initialize() is called
Decrypting encrypted features when provided with the client key, e.g. .builder().encryptionKey(clientKey)
Caching features (in-memory)
Refreshing features

If you wish to manage fetching, refreshing, and caching features on your own, you can choose to not implement this class.

RecommendationThis class should be implemented as a singleton class as it includes caching and refreshing functionality.

If you have more than one SDK endpoint you’d like to implement, you can extend the GBFeaturesRepository class with your own class to make it easier to work with dependency injection frameworks. Each of these instances should be singletons.

Fetching the features

You will need to create a singleton instance of the GBFeaturesRepository class either by implementing its .builder() or by using its constructor. Then, you would call myGbFeaturesRepositoryInstance.initialize() in order to make the initial (blocking) request to fetch the features. Then, you would call myGbFeaturesRepositoryInstance.getFeaturesJson() and provided that to the GBContext initialization.

GBFeaturesRepository featuresRepository = GBFeaturesRepository
    .builder()
    .apiHost("https://cdn.growthbook.io")
    .clientKey("<environment_key>") // replace with your client key
    .encryptionKey("<client-key-for-decrypting>") // optional, nullable
    .refreshStrategy(FeatureRefreshStrategy.SERVER_SENT_EVENTS) // optional; options: STALE_WHILE_REVALIDATE, SERVER_SENT_EVENTS (default: STALE_WHILE_REVALIDATE)
    .build();

// Optional callback for getting updates when features are refreshed
featuresRepository.onFeaturesRefresh(new FeatureRefreshCallback() {
    @Override
    public void onRefresh(String featuresJson) {
        System.out.println("Features have been refreshed");
        System.out.println(featuresJson);
    }
});

try {
    featuresRepository.initialize();
} catch (FeatureFetchException e) {
    // TODO: handle the exception
    e.printStackTrace();
}

// Initialize the GrowthBook SDK with the GBContext and features
GBContext context = GBContext
    .builder()
    .featuresJson(featuresRepository.getFeaturesJson())
    .attributesJson(userAttributesJson)
    .build();

GrowthBook growthBook = new GrowthBook(context);

val featuresRepository = GBFeaturesRepository(
    "https://cdn.growthbook.io",
    "<environment_key>",
    "<client-key-for-decrypting>", // optional, nullable
    30,
).apply {
    // Optional callback for getting updates when features are refreshed
    onFeaturesRefresh {
        println("Features have been refreshed \n $it")
    }
}

// Fetch the features
try {
    featuresRepository.initialize()
} catch (e: FeatureFetchException) {
    // TODO: handle the exception
    e.printStackTrace()
}

// Initialize the GrowthBook SDK with the GBContext and features
val context = GBContext
    .builder()
    .featuresJson(featuresRepository.featuresJson)
    .attributesJson(userAttributes)
    .build()

val growthBook = GrowthBook(context)

For more references, see the Examples below.

Caching and refreshing behavior

As of version 0.9.0, there are 2 refresh strategies available.

Stale While Revalidate

This is the default strategy but can be explicitly stated by passing FeatureRefreshStrategy.STALE_WHILE_REVALIDATE as the refresh strategy option to the GBFeaturesRepository builder or constructor. The GBFeaturesRepository will automatically refresh the features when the features become stale. Features are considered stale every 60 seconds. This amount is configurable with the ttlSeconds option. When you fetch features and they are considered stale, the stale features are returned from the getFeaturesJson() method and a network call to refresh the features is enqueued asynchronously. When that request succeeds, the features are updated with the newest features, and the next call to getFeaturesJson() will return the refreshed features.

Server-Sent Events

This is a new strategy that can be enabled by passing FeatureRefreshStrategy.SERVER_SENT_EVENTS as the refresh strategy option to the GBFeaturesRepository builder or constructor. If you’re using GrowthBook Cloud , this is ready for you to use. If you are self-hosting, you will need to set up the GrowthBook Proxy to enable it.

Overriding Feature Values

The Java SDK allows you to override feature values and experiments using the URL.

Force Experiment Variations

You can force an experiment variation by passing the experiment key and variation index as query parameters in the URL you set on the GBContext. For example, if you add ?my-experiment-id=2 to the URL, users will be forced into the variation at index 2 in the variations list when evaluating the experiment with key my-experiment-id.

Force Feature Values via the URL

You can force a value for a feature by passing the key, prefixed by gb~, and the URI-encoded value in the URL’s query parameters. You must also set allowUrlOverrides to true when building your GBContext in order to enable this feature as it is not enabled by default.

GBContext context = GBContext
    .builder()
    .url("http://localhost:8080/url-feature-force?gb~dark_mode=true&gb~donut_price=3.33&gb~banner_text=Hello%2C%20everyone!%20I%20hope%20you%20are%20all%20doing%20well!")
    .allowUrlOverrides(true)
    .build();

The above code sample sets the following:

dark_mode: true
banner_text: "Hello, everyone! I hope you are all doing well!"
donut_price: 3.33

Supported types

Type	Value
`String`	A URI-encoded string value
`Float`	A float value, e.g. `3.33`
`Double`	A double value, e.g. `3.33`
`Integer`	An integer value, e.g. `1337`
`Boolean`	A boolean value, e.g. `true` or `false`. You can also represent boolean values with on/off state as `on` or `off` or binary values `1` or `0`.
JSON as `Gson`-deserializable	A class that can be deserialized using Gson and that does not have any dependencies on custom type adapters.
JSON as `String`	A URI-encoded string value that should be a valid JSON string that you can deserialize with your own JSON deserialization implementation.

The value passed in the URL is cast at runtime based on the generic type argument passed in when evaluating the feature. This means that when you call <ValueType>getFeatureValue(), what you pass into the URL must successfully cast as ValueType otherwise the value in the URL will be ignored. All keys must be prefixed with gb~.

Using with Proguard and R8

Many Android projects use code-shrinking and obfuscation tools like Proguard and R8 in production. If you are experiencing unexpected feature evaluation results with your release Android builds that do not occur in your debug builds, it’s most likely related to this. You will need to add the following to your proguard-rules.pro file to ensure that all of the GrowthBook SDK classes are kept so that your features are evaluated properly in projects that use Proguard and R8:

# Growthbook Java SDK classes
-keep class growthbook.sdk.java.** { *; }

Code Examples

Web Framework Integration with Spring RestController

@RestController
public class FeatureController {

    // Singleton enhanced client instance
    private final GrowthBookClient growthBookClient;

    @Autowired
    public FeatureController() {
        // build options to configure your Growthbook instance
        Options options = Options.builder()
                .apiHost("https://cdn.growthbook.io")
                .clientKey("sdk-abc123")
                .build();

        // Create growthbook instance using the options you need
        this.growthBookClient = new GrowthBookClient(options);

        // Initialize features once
        this.growthBookClient.initialize();
    }

    @GetMapping("/api/features")
    public ResponseEntity<Map<String, Object>> getFeatures(HttpServletRequest request) {
        // Create user context per request
        UserContext userContext = createUserContext(request);

        // Evaluate features using shared client
        Map<String, Object> features = new HashMap<>();
        features.put("darkMode", growthBookClient.isOn("dark-mode", userContext));
        features.put("maxItems", growthBookClient.getFeatureValue("max-items", 10, userContext));
        features.put("newLayout", growthBookClient.isOn("new-layout", userContext));

        return ResponseEntity.ok(features);
    }

    @GetMapping("/api/user/{userId}/features")
    public ResponseEntity<Map<String, Object>> getUserFeatures(@PathVariable String userId) {
        // Create user-specific context
        UserContext userContext = UserContext.builder()
            .attributesJson(String.format("{\"id\":\"%s\",\"loggedIn\":true}", userId))
            .build();

        // Evaluate features for specific user
        Map<String, Object> features = new HashMap<>();
        features.put("premiumFeature", growthBookClient.isOn("premium-feature", userContext));
        features.put("theme", growthBookClient.getFeatureValue("theme", "light", userContext));

        return ResponseEntity.ok(features);
    }

    private UserContext createUserContext(HttpServletRequest request) {
        // Extract user attributes from request
        String userId = getUserIdFromSession(request);
        String userAgent = request.getHeader("User-Agent");
        String country = getCountryFromRequest(request);

        // Build attributes JSON
        String attributesJson = String.format(
            "{\"id\":\"%s\",\"userAgent\":\"%s\",\"country\":\"%s\",\"loggedIn\":%s}",
            userId, userAgent, country, userId != null
        );

        return UserContext.builder()
            .attributesJson(attributesJson)
            .build();
    }

    private String getUserIdFromSession(HttpServletRequest request) {
        // Your implementation to extract user ID from session/JWT/etc
        return request.getSession().getAttribute("userId") != null
            ? request.getSession().getAttribute("userId").toString()
            : null;
    }

    private String getCountryFromRequest(HttpServletRequest request) {
        // Your implementation to determine user's country
        return request.getHeader("CF-IPCountry"); // Example using Cloudflare header
    }
}

​Installation

​Gradle

​Maven

​Usage

​Enhanced Client (Recommended)

​Basic Enhanced Client Usage

​Using the Enhanced Client with Different User Contexts

​Thread Safety Note

​Traditional Usage

​GrowthBook context

​Using the GBContext builder

​Using the GBContext constructor

​Features

​Attributes

​Secure Attributes

​Using Features

​isOn() / isOff()

​getFeatureValue(featureKey, defaultValue)

​evalFeature(String)

​Inline Experiments

​Inline experiment return value ExperimentResult

​Tracking feature usage and experiment impressions

​Tracking Callback

​Feature Usage Callback

​Experiment Run Callback

​Multiple Callback Subscriptions

​Working with Encrypted features

​Fetching, Caching, and Refreshing features with GBFeaturesRepository

​Fetching the features

​Caching and refreshing behavior

Stale While Revalidate

Server-Sent Events

​Overriding Feature Values

​Force Experiment Variations

​Force Feature Values via the URL

​Supported types

​Using with Proguard and R8

​Code Examples

​Web Framework Integration with Spring RestController

​Additional Examples

​Further Reading

​Supported Features

Installation

Gradle

Maven

Usage

Enhanced Client (Recommended)

Basic Enhanced Client Usage

Using the Enhanced Client with Different User Contexts

Thread Safety Note

Traditional Usage

GrowthBook context

Using the GBContext builder

Using the GBContext constructor

Features

Attributes

Secure Attributes

Using Features

isOn() / isOff()

getFeatureValue(featureKey, defaultValue)

evalFeature(String)

Inline Experiments

Inline experiment return value ExperimentResult

Tracking feature usage and experiment impressions

Tracking Callback

Feature Usage Callback

Experiment Run Callback

Multiple Callback Subscriptions

Working with Encrypted features

Fetching, Caching, and Refreshing features with GBFeaturesRepository

Fetching the features

Caching and refreshing behavior

Overriding Feature Values

Force Experiment Variations

Force Feature Values via the URL

Supported types

Using with Proguard and R8

Code Examples

Web Framework Integration with Spring RestController

Additional Examples

Further Reading

Supported Features