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Configuration Core module.
There is a newer version: 4.1.1
/*
 * Copyright (c) 2020 Oracle and/or its affiliates.
 *
 * 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 io.helidon.config;

import java.util.Optional;

import io.helidon.config.spi.ChangeWatcher;
import io.helidon.config.spi.PollingStrategy;
import io.helidon.config.spi.RetryPolicy;
import io.helidon.config.spi.Source;

/**
 * Source options as a super set of all possible combinations of source implementation.
 * When used as a base class, together with {@link io.helidon.config.AbstractSourceBuilder}, you can set up any
 * source type.
 *
 * @see io.helidon.config.AbstractSourceBuilder
 * @see io.helidon.config.AbstractConfigSource
 * @see io.helidon.config.AbstractConfigSourceBuilder
 */
public class AbstractSource implements Source {
    // any source
    private final boolean optional;
    private final Optional retryPolicy;
    // pollable source
    private final Optional pollingStrategy;
    // watchable source
    private final Optional> changeWatcher;

    /**
     * A new instance configured from the provided builder.
     * The builder is used to set the following:
     * 
     *     {@link #optional()} - for any source, whether the content must be present, or is optional
     *     {@link #retryPolicy()} - for any source, policy used to retry attempts at reading the content
     *     {@link #pollingStrategy()} - for {@link io.helidon.config.spi.PollableSource}, the polling strategy (if any)
     *     {@link #changeWatcher()} - for {@link io.helidon.config.spi.WatchableSource}, the change watcher (if any)
     * 
     * @param builder builder used to read the configuration options
     */
    @SuppressWarnings("unchecked")
    protected AbstractSource(AbstractSourceBuilder builder) {
        this.optional = builder.isOptional();
        this.pollingStrategy = builder.pollingStrategy();
        this.retryPolicy = builder.retryPolicy();
        this.changeWatcher = builder.changeWatcher().map(it -> (ChangeWatcher