edu.utah.further.core.util.context.EnumAliasService.java Source code

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Here is the source code for edu.utah.further.core.util.context.EnumAliasService.java

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/**
 * Copyright (C) [2013] [The FURTHeR Project]
 *
 * 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 edu.utah.further.core.util.context;

import static edu.utah.further.core.api.text.StringUtil.quote;
import static org.slf4j.LoggerFactory.getLogger;

import java.util.Set;

import org.apache.commons.collections15.BidiMap;
import org.apache.commons.collections15.bidimap.DualHashBidiMap;
import org.slf4j.Logger;

import edu.utah.further.core.api.collections.CollectionUtil;
import edu.utah.further.core.api.context.Alias;
import edu.utah.further.core.api.context.Labeled;
import edu.utah.further.core.api.exception.ApplicationException;
import edu.utah.further.core.api.lang.ReflectionUtil;
import edu.utah.further.core.util.io.ResourceMatchingFactoryBean;

/**
 * This class builds a map of aliases-to-enumerated-types. Includes only enumerated types
 * annotated by {@link Alias}.
 * <p>
 * -----------------------------------------------------------------------------------<br>
 * (c) 2008-2013 FURTHeR Project, AVP Health Sciences IT Office, University of Utah<br>
 * Contact: {@code <further@utah.edu>}<br>
 * Biomedical Informatics, 26 South 2000 East<br>
 * Room 5775 HSEB, Salt Lake City, UT 84112<br>
 * Day Phone: 1-801-581-4080<br>
 * -----------------------------------------------------------------------------------
 *
 * @author Oren E. Livne {@code <oren.livne@utah.edu>}
 * @version Oct 13, 2008
 */
// @Service("enumAlias") // no default constructor
public class EnumAliasService extends ResourceMatchingFactoryBean<Class<?>> {
    // ========================= CONSTANTS =================================

    /**
     * A logger that helps identify this class' printouts.
     */
    private static final Logger log = getLogger(EnumAliasService.class);

    // ========================= DEPENDENCIES ==============================

    // ========================= FIELDS ====================================

    /**
     * The list of annotated classes. May be set by a constructor or by scanning for
     * annotations.
     */
    private volatile BidiMap<String, Class<? extends Enum<?>>> enumAliases;

    /**
     * A set of enumerated classes that implement the {@link Labeled} interface.
     */
    private volatile Set<Class<? extends Enum<?>>> labeledClasses;

    // ========================= CONSTRUCTORS ==============================

    // ========================= METHODS ===================================

    /**
     * Return the enum aliases map.
     *
     * @return the enum aliases map
     */
    public BidiMap<String, Class<? extends Enum<?>>> getEnumAliases() {
        // using the double-checked locking with volatile
        // @see http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
        if (enumAliases == null) {
            synchronized (this) {
                if (enumAliases == null) {
                    enumAliases = initializeEnumAliases();
                }
            }
        }
        // Defensive copy. TODO: move to CollectionUtil as a generic factory method
        return new DualHashBidiMap<>(enumAliases);
    }

    /**
     * Return the labeled classes set.
     *
     * @return the labeled classes set
     */
    public Set<Class<? extends Enum<?>>> getLabeledClasses() {
        // using the double-checked locking with volatile
        // @see http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
        if (labeledClasses == null) {
            synchronized (this) {
                if (labeledClasses == null) {
                    labeledClasses = initializeLabeledClasses();
                }
            }
        }
        return CollectionUtil.newSet(labeledClasses);
    }

    // ========================= DEPENDENCY INJECTION ======================

    /**
     * Set the static enum alias map field.
     * <p>
     * Warning: do not call this method outside this class. It is meant to be called by
     * Spring when instantiating the singleton instance of this bean.
     */
    @SuppressWarnings("unchecked")
    private BidiMap<String, Class<? extends Enum<?>>> initializeEnumAliases() {
        final Class<Alias> annotationClass = Alias.class;
        // TODO: move to CollectionUtil as a generic factory method
        final BidiMap<String, Class<? extends Enum<?>>> map = new DualHashBidiMap<>();
        for (final Class<?> annotatedClass : this.getObject()) {
            if (annotatedClass.isEnum()) {
                final String alias = annotatedClass.getAnnotation(annotationClass).value();
                final Class<? extends Enum<?>> otherClass = map.get(alias);
                if (otherClass != null) {
                    // This is the second time that we encountered the alias
                    // key, signal name collision
                    final String errorMessage = "Enum alias collision!!! Both " + otherClass + ", " + annotatedClass
                            + " have the same alias: " + quote(alias) + ". Rename the @"
                            + annotationClass.getSimpleName() + " annotation value one of them.";
                    // Log message before throwing, otherwise Spring will
                    // show an incomprehensible TargetInvocationException
                    // without its cause here.
                    log.error(errorMessage);
                    throw new ApplicationException(errorMessage);
                }
                map.put(alias, (Class<? extends Enum<?>>) annotatedClass);
            }
        }
        return map;
    }

    /**
     * @return
     */
    @SuppressWarnings("unchecked")
    private Set<Class<? extends Enum<?>>> initializeLabeledClasses() {
        final Set<Class<? extends Enum<?>>> set = CollectionUtil.newSet();
        for (final Class<?> annotatedClass : this.getObject()) {
            if (annotatedClass.isEnum() && ReflectionUtil.classIsInstanceOf(annotatedClass, Labeled.class)) {
                set.add((Class<? extends Enum<?>>) annotatedClass);
            }
        }
        return set;
    }

}