net.cassite.daf4j.stream.QueryStream Maven / Gradle / Ivy

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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.*;

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

/**
 * QueryStream查询.

 * 用于查询实体序列
 *
 * @param  实体类型
 */
public class QueryStream extends QueryStreamBase> implements Iterable {
        public QueryStream(E entity, DataAccess dataAccess) {
                super(entity, dataAccess);
        }

        /**
         * 将结果转换为List[实体]
         *
         * @return List类型的结果
         */
        public List list() {
                return dataAccess.list(entity, andOr, parameter);
        }

        /**
         * 执行计数
         *
         * @return long类型的计数结果
         */
        public long count() {
                return DataUtils.executeCount(entity, andOr, parameter, dataAccess);
        }

        /**
         * 映射所有非集合字段
         *
         * @return 映射后的stream
         */
        public QueryProjectionStream mapAll() {
                return map((Focus) null);
        }

        /**
         * 映射指定字段/表达式
         *
         * @param focus 要映射的字段/表达式
         * @return 映射后的stream
         */
        public QueryProjectionStream map(Focus focus) {
                QueryParameterWithFocus p = new QueryParameterWithFocus(parameter, focus);
                return new QueryProjectionStream(entity, dataAccess, andOr, p);
        }

        /**
         * 映射到整型的stream
         *
         * @param data 表示整型的字段
         * @return 映射后的stream
         */
        public QueryIntStream mapToInt(DataComparable data) {
                return new QueryIntStream(entity, dataAccess, andOr, parameter, data);
        }

        /**
         * 映射到Long的stream
         *
         * @param data 表示Long的字段
         * @return 映射后的stream
         */
        public QueryLongStream mapToLong(DataComparable data) {
                return new QueryLongStream(entity, dataAccess, andOr, parameter, data);
        }

        /**
         * 映射到Double的stream
         *
         * @param data 表示Double的字段
         * @return 映射后的stream
         */
        public QueryDoubleStream mapToDouble(DataComparable data) {
                return new QueryDoubleStream(entity, dataAccess, andOr, parameter, data);
        }

        public PreResult subQuery() {
                PreResult preResult = new PreResult(dataAccess, entity, andOr);
                preResult.parameter = this.parameter;
                return preResult;
        }

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

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