| /* |
| * 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.drill.exec.server.options; |
| |
| import java.util.Iterator; |
| |
| import org.apache.drill.shaded.guava.com.google.common.collect.Iterables; |
| |
| /** |
| * An {@link OptionManager} which allows for falling back onto another |
| * {@link OptionManager} when retrieving options. |
| * <p/> |
| * {@link FragmentOptionManager} and {@link SessionOptionManager} use |
| * {@link SystemOptionManager} as the fall back manager. |
| * {@link QueryOptionManager} uses {@link SessionOptionManager} as the fall back |
| * manager. |
| */ |
| public abstract class FallbackOptionManager extends BaseOptionManager { |
| |
| protected final OptionManager fallback; |
| |
| public FallbackOptionManager(OptionManager fallback) { |
| /** |
| * TODO(DRILL-2097): Add a Preconditions.checkNotNull(fallback, "A fallback manager must be provided.") and remove |
| * the null check in {@link #getOption(String)}. This is not added currently only to avoid modifying the long list |
| * of test files. |
| */ |
| this.fallback = fallback; |
| } |
| |
| @Override |
| public Iterator<OptionValue> iterator() { |
| return Iterables.concat(fallback, getLocalOptions()).iterator(); |
| } |
| |
| @Override |
| public OptionValue getOption(final String name) { |
| final OptionValue value = getLocalOption(name); |
| if (value == null && fallback != null) { |
| return fallback.getOption(name); |
| } else { |
| return value; |
| } |
| } |
| |
| /** |
| * Gets the option values managed by this manager as an iterable. |
| * |
| * @return iterable of option values |
| */ |
| abstract Iterable<OptionValue> getLocalOptions(); |
| |
| /** |
| * Gets the option value from this manager without falling back. |
| * |
| * @param name the option name |
| * @return the option value, or null if the option does not exist locally |
| */ |
| abstract OptionValue getLocalOption(String name); |
| |
| @Override |
| public OptionDefinition getOptionDefinition(String name) { |
| return fallback.getOptionDefinition(name); |
| } |
| |
| @Override |
| public OptionList getOptionList() { |
| final OptionList list = new OptionList(); |
| for (final OptionValue value : getLocalOptions()) { |
| list.add(value); |
| } |
| return list; |
| } |
| } |