net.derquinse.common.orm.Entities.java Source code

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Here is the source code for net.derquinse.common.orm.Entities.java

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/*
 * Copyright (C) the original author or authors.
 *
 * 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 net.derquinse.common.orm;

import static com.google.common.base.Preconditions.checkNotNull;

import java.io.Serializable;
import java.util.Map;
import java.util.Set;

import net.derquinse.common.base.NotInstantiable;

import com.google.common.base.Objects;
import com.google.common.base.Predicates;
import com.google.common.collect.Iterables;
import com.google.common.collect.Maps;

/**
 * Support methods for entities.
 * @author Andres Rodriguez
 */
public final class Entities extends NotInstantiable {
    private Entities() {
    }

    /** Returns the id of the provided entity or {@code null } if the argument is {@code null}. */
    public static <ID extends Serializable, T extends Entity<ID>> ID entityId(Entity<ID> entity) {
        if (entity == null) {
            return null;
        }
        return entity.getId();
    }

    /**
     * Checks if two entities are both {@code null} or have the same id (that can be {@code null}.
     */
    public static <ID extends Serializable, T extends Entity<ID>> boolean idEquals(Entity<ID> entity1,
            Entity<ID> entity2) {
        return Objects.equal(entityId(entity1), entityId(entity2));
    }

    /**
     * Checks if an object is an instance of an entity type and its id is equals to the provided
     * entity id.
     * @param entity Entity.
     * @param type Entity type.
     * @param obj Object to check.
     * @return The object casts to type if neither the object nor the entity are null, obj is an
     *         instance of type and the object and the entity have the same id (even if the id is
     *         null). Null otherwise.
     */
    public static <ID extends Serializable, T extends Entity<ID>> T idEquals(Entity<ID> entity,
            Class<? extends T> type, Object obj) {
        if (entity == null || obj == null) {
            return null;
        }
        if (type.isInstance(obj)) {
            T other = type.cast(obj);
            if (Objects.equal(entity.getId(), other.getId())) {
                return other;
            }
        }
        return null;
    }

    /**
     * Returns the hash code of the id of the entity. If either the entity or its id are null a
     * constant number is returned.
     */
    public static int idHashCode(Entity<?> entity) {
        if (entity != null) {
            Object id = entity.getId();
            if (id != null) {
                return id.hashCode();
            }
        }
        return 1046;
    }

    /** Clears the target map and inserts every non-null element from the source one. */
    public static <K, V> void pushMap(Map<K, V> target, Map<? extends K, ? extends V> source) {
        checkNotNull(target);
        target.clear();
        if (source != null) {
            target.putAll(Maps.filterKeys(Maps.filterValues(source, Predicates.notNull()), Predicates.notNull()));
        }
    }

    /** Clears the target set and inserts every non-null element from the source iterable. */
    public static <T> void pushSet(Set<T> target, Iterable<? extends T> source) {
        checkNotNull(target);
        target.clear();
        if (source != null) {
            Iterables.addAll(target, Iterables.filter(source, Predicates.notNull()));
        }
    }

}