# QueryBuilderImpl.java

    /*
     * Copyright 2007-2009 Niclas Hedhman.
     * Copyright 2008 Alin Dreghiciu.
     *
     * 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.runtime.query;

    import org.qi4j.api.composite.Composite;
    import org.qi4j.api.query.Query;
    import org.qi4j.api.query.QueryBuilder;
    import org.qi4j.api.query.QueryExpressions;
    import org.qi4j.functional.Specification;
    import org.qi4j.spi.query.EntityFinder;
    import org.qi4j.spi.query.QueryBuilderSPI;
    import org.qi4j.spi.query.QuerySource;

    /**
     * Default implementation of {@link QueryBuilder}
     */
    final class QueryBuilderImpl<T>
        implements QueryBuilder<T>, QueryBuilderSPI<T>
    {

        /**
         * Entity finder to be used to locate entities.
         */
        private final EntityFinder entityFinder;

        /**
         * Type of queried entities.
         */
        private final Class<T> resultType;
        /**
         * Where clause.
         */
        private final Specification<Composite> whereClause;

        /**
         * Constructor.
         *
         * @param entityFinder entity finder to be used to locate entities; canot be null
         * @param resultType   type of queried entities; cannot be null
         * @param whereClause  current where-clause
         */
        QueryBuilderImpl( final EntityFinder entityFinder,
                          final Class<T> resultType,
                          final Specification<Composite> whereClause
        )
        {
            this.entityFinder = entityFinder;
            this.resultType = resultType;
            this.whereClause = whereClause;
        }

        @Override
        @SuppressWarnings( "unchecked" )
        public QueryBuilder<T> where( Specification<Composite> specification )
        {
            if( specification == null )
            {
                throw new IllegalArgumentException( "Where clause cannot be null" );
            }
            if( this.whereClause != null )
            {
                specification = QueryExpressions.and( this.whereClause, specification );
            }
            return new QueryBuilderImpl<>( entityFinder, resultType, specification );
        }

        @Override
        public Query<T> newQuery( Iterable<T> iterable )
        {
            return new QueryImpl<>( resultType, whereClause, new IterableQuerySource( iterable ) );
        }

        // SPI
        @Override
        public Query<T> newQuery( QuerySource querySource )
        {
            return new QueryImpl<>( resultType, whereClause, querySource );
        }
    }