org.apache.sling.featureflags.Feature Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.sling.featureflags;
import org.osgi.annotation.versioning.ConsumerType;
/**
* A feature is defined by its name. Features are registered as OSGi services.
*
* Feature {@link #getName() names} should be globally unique. If multiple
* features have the same name, the feature with the highest service ranking is
* accessible through the {@link Features} service while those with lower
* service rankings are ignored.
*
* This interface is expected to be implemented by feature providers.
*/
@ConsumerType
public interface Feature {
/**
* The name of the feature.
*
* @return The name of this feature which must not be {@code null} or an
* empty string.
*/
String getName();
/**
* The description of the feature.
*
* @return The optional description of this feature, which may be
* {@code null} or an empty string.
*/
String getDescription();
/**
* Checks whether the feature is enabled for the given execution context.
*
* Multiple calls to this method may but are not required to return the same
* value. For example the return value may depend on the time of day, some
* random number or some information provided by the given
* {@link ExecutionContext}.
*
* This method is called by the {@link Feature} manager and is not intended
* to be called by application code directly.
*
* @param context The {@link ExecutionContext} providing a context to
* evaluate whether the feature is enabled or not.
* Implementations must not hold on to this context instance or
* the values provided for longer than executing this method.
* @return {@code true} if this {@code Feature} is enabled in the given
* {@link ExecutionContext}.
*/
boolean isEnabled(ExecutionContext context);
}