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Quickstart

The Eppo Java SDK enables feature flags and experiments in your Java applications with only a few lines of code.

Installation​

You can install the SDK using Gradle or Maven:

implementation 'cloud.eppo:eppo-server-sdk:5.0.0'

Feature Flags​

Initialize the SDK​

Create an SDK key if you don't already have one.

Initialize the SDK with your key:

EppoClient eppoClient = EppoClient.builder(sdkKey).buildAndInit();

Assign a variant​

After initialization, you can access the client with EppoClient.getInstance(). The SDK supports different types of assignments:

String assignedVariation = eppoClient.getStringAssignment(
    "flagKey",
    "subjectKey",
    "defaultValue"
);

// With subject attributes
Attributes subjectAttributes = new Attributes(
  Map.of(
    "country", EppoValue.valueOf("FR"),
    "age", EppoValue.valueOf(60)
  )
);

String assignedVariation = eppoClient.getStringAssignment(
    "flagKey",
    "subjectKey",
    subjectAttributes, 
    "defaultValue"
);

Assignment Types​

The SDK provides different assignment functions based on the type of value you need:

FunctionReturn Type
getStringAssignment()String
getBooleanAssignment()Boolean
getJSONAssignment()JSON object
getIntegerAssignment()Integer
getDoubleAssignment()Double

Experiments​

For experiments, you'll need to add an assignment logger (see AssignmentLogger) when initializing the SDK:

EppoClient.builder(sdkKey)
  .assignmentLogger(assignmentLogData -> {
    // TODO: Send assignment event data to data warehouse
    System.out.println(assignmentLogData);
  })
  .buildAndInit();

After that, you can make assignments the same way as with feature flags.

Contextual Bandits​

For bandits, you'll need both an assignment logger and a bandit logger:

EppoClient.builder(sdkKey)
  .assignmentLogger(assignmentLogData -> {
    // TODO: Send assignment event data to data warehouse
    System.out.println(assignmentLogData);
  })
  .banditLogger(banditLogData -> {
    // TODO: Send bandit event data to data warehouse
    System.out.println(banditLogData);
  })
  .buildAndInit();

Query the bandit for actions​

String flagKey = "shoe-bandit";
String subjectKey = "user123";
DiscriminableAttributes subjectAttributes = new Attributes(
  Map.of(
    "age", EppoValue.valueOf(25),
    "country", EppoValue.valueOf("BG")
  )
);

Actions actions = new BanditActions(
  Map.of(
    "nike",
    new Attributes(
      Map.of(
        "brandAffinity", EppoValue.valueOf(2.3),
        "previouslyPurchased", EppoValue.valueOf(true)
      )
    ),
    "adidas",
    new Attributes(
      Map.of(
        "brandAffinity", EppoValue.valueOf(0.2),
        "previouslyPurchased", EppoValue.valueOf(false)
      )
    )
  )
);

String defaultValue = "control";

BanditResult banditResult = eppoClient.getBanditAction(
  flagKey,
  subjectKey,
  subjectAttributes,
  actions,
  defaultValue
);

if (banditResult.getAction() != null) {
  renderShoeAd(banditResult.getAction());
} else {
  renderDefaultShoeAd();
}