Querydsl返回自定义字段

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我是靠谱客的博主怕孤独悟空，最近开发中收集的这篇文章主要介绍Querydsl返回自定义字段，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

方法一：使用Bean

return queryFactory.select(
                Projections.bean(PersonIDCardDto.class, QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name))
                .from(QIDCard.iDCard, QPerson.person)
                .where(predicate)
                .fetch();

方法二：使用fields

return queryFactory.select(
                Projections.fields(PersonIDCardDto.class, QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name))
                .from(QIDCard.iDCard, QPerson.person)
                .where(predicate)
                .fetch();

方法三：使用构造方法，注意构造方法中参数的顺序

     return queryFactory.select(
                Projections.constructor(PersonIDCardDto.class, QPerson.person.name, QPerson.person.address, QIDCard.iDCard.idNo))
                .from(QIDCard.iDCard, QPerson.person)
                .where(predicate)
                .fetch();

方法四：使用lambda

jpaQueryFactory
                .select(
                        user.username,
                        user.userId,
                        user.nickName,
                        user.birthday
                )
                .from(user)
                .offset(pageable.getOffset())
                .limit(pageable.getPageSize())
                .fetch()
                .stream()
                .map(tuple -> UserDTO.builder()
                        .username(tuple.get(user.username))
                        .nickname(tuple.get(user.nickName))
                        .userId(tuple.get(user.userId).toString())
                        .birthday(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(tuple.get(user.birthday)))
                        .build()
                )
                .collect(Collectors.toList());