extensions/indexing-sql/src/main/java/org/qi4j/index/sql/support/skeletons/SQLSkeletonUtil.java

/*
 * Copyright (c) 2010, Stanislav Muhametsin. All Rights Reserved.
 *
 * 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.qi4j.index.sql.support.skeletons;

import java.lang.reflect.AccessibleObject;
import org.qi4j.api.entity.Queryable;

/* package */ final class SQLSkeletonUtil
{

    /* package */ static boolean isQueryable( AccessibleObject accessor )
    {
        Queryable q = accessor.getAnnotation( Queryable.class );
        return q == null || q.value();
    }

    private SQLSkeletonUtil()
    {
    }

    /**
     * Required for Lazy.
     *
     * @param <T> The result variable type.
     */
    public static interface LazyInit<T, TException extends Throwable>
    {
        T create()
            throws TException;
    }

    /**
     * Non-threadsafe implementation of C#'s Lazy&lt;T&gt;. I wonder if Java has something like this
     * already done?
     *
     * @param <T> The result variable type.
     */
    public static final class Lazy<T, TException extends Throwable>
    {
        private final LazyInit<T, TException> m_init;
        private T m_cachedValue;

        public Lazy( LazyInit<T, TException> init )
        {
            this.m_init = init;
            this.m_cachedValue = null;
        }

        public T getValue()
            throws TException
        {
            if( this.m_cachedValue == null )
            {
                this.m_cachedValue = this.m_init.create();
            }
            return this.m_cachedValue;
        }

        public boolean hasValue()
        {
            return this.m_cachedValue != null;
        }
    }

    public static final class Reference<T>
    {
        private T m_reference;

        public void setReference( T reference )
        {
            this.m_reference = reference;
        }

        public T getReference()
        {
            return this.m_reference;
        }
    }

}