sshd-core/src/main/java/org/apache/sshd/common/NamedFactory.java

/*
 * 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.sshd.common;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.apache.sshd.common.util.Transformer;

/**
 * A named factory is a factory identified by a name.
 * Such names are used mainly in the algorithm negotiation at the beginning of the SSH connection.
 *
 * @param <T> The create object instance type
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
public interface NamedFactory<T> extends Factory<T>, NamedResource {
    /**
     * Utility class to help using NamedFactories
     */
    // CHECKSTYLE:OFF
    final class Utils {
    // CHECKSTYLE:ON

        private Utils() {
            throw new UnsupportedOperationException("No instance allowed");
        }

        /**
         * Create an instance of the specified name by looking up the needed factory
         * in the list.
         *
         * @param factories list of available factories
         * @param name      the factory name to use
         * @param <T>       type of object to create
         * @return a newly created object or {@code null} if the factory is not in the list
         */
        public static <T> T create(Collection<? extends NamedFactory<T>> factories, String name) {
            NamedFactory<? extends T> f = NamedResource.Utils.findByName(name, String.CASE_INSENSITIVE_ORDER, factories);
            if (f != null) {
                return f.create();
            } else {
                return null;
            }
        }

        public static <S extends OptionalFeature, T, E extends NamedFactory<T>> List<NamedFactory<T>> setUpTransformedFactories(
                boolean ignoreUnsupported, Collection<? extends S> preferred, Transformer<? super S, ? extends E> xform) {
            List<NamedFactory<T>> avail = new ArrayList<>(preferred.size());
            for (S f : preferred) {
                if (ignoreUnsupported || f.isSupported()) {
                    avail.add(xform.transform(f));
                }
            }
            return avail;
        }

        public static <T, E extends NamedFactory<T> & OptionalFeature> List<NamedFactory<T>> setUpBuiltinFactories(
                boolean ignoreUnsupported, Collection<? extends E> preferred) {
            List<NamedFactory<T>> avail = new ArrayList<>(preferred.size());
            for (E f : preferred) {
                if (ignoreUnsupported || f.isSupported()) {
                    avail.add(f);
                }
            }

            return avail;
        }
    }
}