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package com.launchdarkly.sdk.server.integrations;
import com.launchdarkly.sdk.EvaluationDetail;
import com.launchdarkly.sdk.LDContext;
import com.launchdarkly.sdk.LDValue;
import com.launchdarkly.sdk.server.FlagsStateOption;
import java.util.Map;
/**
* A Hook is a set of user-defined callbacks that are executed by the SDK at various points of interest. To create
* your own hook with customized logic, implement the {@link Hook} interface.
*
* Hook currently defines an "evaluation" series, which is composed of two stages: "beforeEvaluation" and
* "afterEvaluation". These are executed by the SDK before and after the evaluation of a feature flag.
*
* Multiple hooks may be configured in the SDK. By default, the SDK will execute each hook's beforeEvaluation
* stage in the order they were configured, and afterEvaluation in reverse order. (i.e. myHook1.beforeEvaluation,
* myHook2.beforeEvaluation, myHook2.afterEvaluation, myHook1.afterEvaluation)
*/
public abstract class Hook {
private final HookMetadata metadata;
/**
* @return the hooks metadata
*/
public HookMetadata getMetadata() {
return metadata;
}
/**
* Creates an instance of {@link Hook} with the given name which will be put into its metadata.
*
* @param name a friendly naem for the hooks
*/
public Hook(String name) {
metadata = new HookMetadata(name) {};
}
/**
* {@link #beforeEvaluation(EvaluationSeriesContext, Map)} is executed by the SDK at the start of the evaluation of
* a feature flag. It will not be executed as part of a call to
* {@link com.launchdarkly.sdk.server.LDClient#allFlagsState(LDContext, FlagsStateOption...)}.
*
* To provide custom data to the series which will be given back to your {@link Hook} at the next stage of the
* series, return a map containing the custom data. You should initialize this map from the {@code seriesData}.
*
*
* {@code
* HashMap customData = new HashMap<>(seriesData);
* customData.put("foo", "bar");
* return Collections.unmodifiableMap(customData);
* }
*
*
* @param seriesContext container of parameters associated with this evaluation
* @param seriesData immutable data from the previous stage in evaluation series. {@link #beforeEvaluation(EvaluationSeriesContext, Map)}
* is the first stage in this series, so this will be an immutable empty map.
* @return a map containing custom data that will be carried through to the next stage of the series
*/
public Map beforeEvaluation(EvaluationSeriesContext seriesContext, Map seriesData) {
// default implementation is no-op
return seriesData;
}
/**
* {@link #afterEvaluation(EvaluationSeriesContext, Map, EvaluationDetail)} is executed by the SDK at the after the
* evaluation of a feature flag. It will not be executed as part of a call to
* {@link com.launchdarkly.sdk.server.LDClient#allFlagsState(LDContext, FlagsStateOption...)}.
*
* This is currently the last stage of the evaluation series in the {@link Hook}, but that may not be the case in
* the future. To ensure forward compatibility, return the {@code seriesData} unmodified.
*
*
* {@code
* String value = (String) seriesData.get("foo");
* doAThing(value);
* return seriesData;
* }
*
*
* @param seriesContext container of parameters associated with this evaluation
* @param seriesData immutable data from the previous stage in evaluation series. {@link #beforeEvaluation(EvaluationSeriesContext, Map)}
* is the first stage in this series, so this will be an immutable empty map.
* @param evaluationDetail the result of the evaluation that took place before this hook was invoked
* @return a map containing custom data that will be carried through to the next stage of the series (if added in the future)
*/
public Map afterEvaluation(EvaluationSeriesContext seriesContext, Map seriesData,
EvaluationDetail evaluationDetail) {
// default implementation is no-op
return seriesData;
}
}