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core module for querydsl
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/*
 * Copyright 2011, Mysema Ltd
 * 
 * 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 com.mysema.query.support;

import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import javax.annotation.Nullable;

import com.mysema.commons.lang.CloseableIterator;
import com.mysema.commons.lang.IteratorAdapter;
import com.mysema.query.NonUniqueResultException;
import com.mysema.query.Projectable;
import com.mysema.query.ResultTransformer;
import com.mysema.query.Tuple;
import com.mysema.query.types.Expression;

/**
 * ProjectableQuery extends the {@link QueryBase} class to provide default
 * implementations of the methods of the {@link Projectable} interface
 *
 * @author tiwe
 */
public abstract class ProjectableQuery>
        extends QueryBase implements Projectable {

    public ProjectableQuery(QueryMixin queryMixin) {
        super(queryMixin);
    }

    @Override
    public List list(Expression... args) {
        return IteratorAdapter.asList(iterate(args));
    }

    @Override
    public  List list(Expression projection) {
        return IteratorAdapter.asList(iterate(projection));
    }

    @Override
    public final  Map map(Expression key, Expression value) {
        List list = list(key, value);
        Map results = new LinkedHashMap(list.size());
        for (Tuple row : list) {
            results.put(row.get(key), row.get(value));
        }
        return results;
    }

    @Override
    public final boolean notExists() {
        return !exists();
    }

    @Override
    public final Tuple singleResult(Expression... args) {
        return limit(1).uniqueResult(args);
    }

    @Override
    public final  RT singleResult(Expression expr) {
        return limit(1).uniqueResult(expr);
    }

    @Override
    public  T transform(ResultTransformer transformer) {
        return transformer.transform(this);
    }
    
    @Nullable
    protected  T uniqueResult(CloseableIterator it) {
        try{
            if (it.hasNext()) {
                T rv = it.next();
                if (it.hasNext()) {
                    throw new NonUniqueResultException();
                }
                return rv;
            } else {
                return null;
            }
        }finally{
            it.close();
        }
    }


}