QueryDSL自定義實體映射，Predicate多條件查詢

 @Override
    public List<ProjectStatusDTO> getProjectStatus(Long departId) {
        QProject qProject = QProject.project;
        Predicate predicate = qProject.isNotNull().or(qProject.isNull());
        predicate = StringUtils.isEmpty(departId) ? predicate : ExpressionUtils.and(predicate, qProject.departId.eq(departId));

        List<ProjectStatusDTO> projectStatusDTOList = jpaQueryFactory.select(
                Projections.bean(
                        ProjectStatusDTO.class,
                        qProject.status,
                        qProject.id.count().as("count")
                )
        )
                .from(qProject)
                .where(predicate)
                .groupBy(qProject.status)
                .fetch();
        return projectStatusDTOList;
    }

核心代碼：

 Projections.bean(
                        ProjectStatusDTO.class,
                        qProject.status,
                        qProject.id.count().as("count")
                )

注意點：

如果實體中的字段屬性和自定義的對象的屬性不一樣，請使用   .as("自定義對象中的屬性名稱")