com.google.cloud.dataflow.sdk.options.DefaultValueFactory Maven / Gradle / Ivy

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/*
 * Copyright (C) 2015 Google Inc.
 *
 * Licensed 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 com.google.cloud.dataflow.sdk.options;

/**
 * An interface used with {@link Default.InstanceFactory} annotation to specify the class that will
 * be an instance factory to produce default values for a given getter on {@link PipelineOptions}.
 * When a property on a {@link PipelineOptions} is fetched, and is currently unset, the default
 * value factory will be instantiated and invoked.
 * 
 * Care must be taken to not produce an infinite loop when accessing other fields on the
 * {@link PipelineOptions} object.
 *
 * @param  The type of object this factory produces.
 */
public interface DefaultValueFactory {
  /**
   * Creates a default value for a getter marked with {@link Default.InstanceFactory}.
   *
   * @param options The current pipeline options.
   * @return The default value to be used for the given pipeline options.
   */
  T create(PipelineOptions options);
}