org.apache.aurora.common.args.Verifiers.java Source code

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Here is the source code for org.apache.aurora.common.args.Verifiers.java

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/**
 * 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 org.apache.aurora.common.args;

import java.lang.annotation.Annotation;
import java.util.Map;

import javax.annotation.Nullable;

import com.google.common.collect.ImmutableMap;
import com.google.common.reflect.TypeToken;

import org.apache.aurora.common.args.apt.Configuration;
import org.apache.aurora.common.collections.Pair;

/**
 * Utility class to manage relationships between constraints and types.
 *
 * @author William Farner
 */
public final class Verifiers {

    private final ImmutableMap<Pair<Class<?>, Class<? extends Annotation>>, Verifier<?>> registry;

    private Verifiers(Map<Pair<Class<?>, Class<? extends Annotation>>, Verifier<?>> registry) {

        this.registry = ImmutableMap.copyOf(registry);
    }

    @Nullable
    <T> Verifier<T> get(TypeToken<T> type, Annotation constraint) {
        for (Map.Entry<Pair<Class<?>, Class<? extends Annotation>>, Verifier<?>> entry : registry.entrySet()) {
            if (entry.getKey().getSecond() == constraint.annotationType()
                    && entry.getKey().getFirst().isAssignableFrom(type.getRawType())) {

                // We control the registry which ensures a proper mapping of class -> verifier.
                @SuppressWarnings("unchecked")
                Verifier<T> verifier = (Verifier<T>) entry.getValue();
                return verifier;
            }
        }

        return null;
    }

    static Verifiers fromConfiguration(Configuration configuration) {
        ImmutableMap.Builder<Pair<Class<?>, Class<? extends Annotation>>, Verifier<?>> registry = ImmutableMap
                .builder();

        for (Configuration.VerifierInfo info : configuration.verifierInfo()) {
            Class<?> verifiedType = forName(info.verifiedType);
            Class<? extends Annotation> verifyingAnnotation = forName(info.verifyingAnnotation);
            Class<? extends Verifier<?>> verifierClass = forName(info.verifierClass);
            try {
                registry.put(Pair.<Class<?>, Class<? extends Annotation>>of(verifiedType, verifyingAnnotation),
                        verifierClass.newInstance());
            } catch (InstantiationException e) {
                throw new Configuration.ConfigurationException(e);
            } catch (IllegalAccessException e) {
                throw new Configuration.ConfigurationException(e);
            }
        }
        return new Verifiers(registry.build());
    }

    @SuppressWarnings("unchecked")
    private static <T> Class<T> forName(String name) {
        try {
            return (Class<T>) Class.forName(name);
        } catch (ClassNotFoundException e) {
            throw new Configuration.ConfigurationException(e);
        }
    }
}