io.cdap.wrangler.registry.CompositeDirectiveRegistry Maven / Gradle / Ivy
/*
* Copyright © 2017-2019 Cask Data, 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 io.cdap.wrangler.registry;
import com.google.common.collect.Iterables;
import io.cdap.wrangler.api.DirectiveLoadException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.annotation.Nullable;
/**
* This class implements a Composition of multiple registries.
*
* It implements the DirectiveRegistry interface. Search for a directives
* uses the order of the directives specified at the construction time.
*
* If the directive is not found in any of the registry, then a null
* is returned.
*/
public final class CompositeDirectiveRegistry implements DirectiveRegistry {
private final DirectiveRegistry[] registries;
public CompositeDirectiveRegistry(DirectiveRegistry ... registries) {
this.registries = registries;
}
/**
* This method looks for the directive in all the registered registries.
*
* The order of search is as specified by the collection order. Upon finding
* the first valid instance of directive, the DirectiveInfo is returned.
*
* @param directive of the directive to be retrived from the registry.
* @return an instance of {@link DirectiveInfo} if found, else null.
*/
@Nullable
@Override
public DirectiveInfo get(String namespace, String directive) throws DirectiveLoadException {
for (int i = 0; i < registries.length; ++i) {
DirectiveInfo info = registries[i].get(namespace, directive);
if (info != null) {
return info;
}
}
return null;
}
@Override
public void reload(String namespace) throws DirectiveLoadException {
for (int idx = 0; idx < registries.length; ++idx) {
registries[idx].reload(namespace);
}
}
/**
* @return Returns an iterator to iterate through all the DirectiveInfo objects
* maintained within the registry.
*/
@Override
public Iterable list(String namespace) {
List> lists = new ArrayList<>();
for (DirectiveRegistry registry : registries) {
lists.add(registry.list(namespace));
}
return Iterables.concat(lists);
}
/**
* Closes any resources acquired during initialization or otherwise.
*/
@Override
public void close() throws IOException {
for (int idx = 0; idx < registries.length; ++idx) {
registries[idx].close();
}
}
}