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A library provides facade api for data accessing.

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package net.cassite.daf4j.stream;

import net.cassite.daf4j.AndOr;
import net.cassite.daf4j.DataAccess;
import net.cassite.daf4j.QueryParameterWithFocus;

import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 * Stream风格查询

 * 用于查询{别名:值}序列
 *
 * @param  实体类型
 */
public class QueryProjectionStream extends QueryStreamBase> implements Iterable> {

        QueryProjectionStream(E entity, DataAccess dataAccess, AndOr andOr, QueryParameterWithFocus parameter) {
                super(entity, dataAccess);
                this.andOr = andOr;
                this.parameter = parameter;
        }

        /**
         * 执行映射,列出List[Map[]]
         *
         * @return List[Map[]]格式的映射结果
         */
        public List> list() {
                return dataAccess.projection(entity, andOr, (QueryParameterWithFocus) parameter);
        }

        @Override
        public Iterator> iterator() {
                return list().iterator();
        }

        /**
         * 获取第一条记录
         *
         * @return 第一条记录
         */
        public Map first() {
                List> list = this.limit(1).list();
                return list == null || list.size() == 0 ? null : list.get(0);
        }
}