Java Specification CriteriaBuilder 复杂查询

Question

我对规范、构建器、查询不是很有经验，我必须做一个相当复杂的查询，就像这样:

select * from table where
   code in ('code1',  'code2' //codes) and
    (
        (
            date between "2020-03-23 //from" and "2020-03-30 //to"
            and
            status in ('Status1' , 'Status2' //status)
        )
        or
        (
            date between "2021-03-23" and "2021-03-30"
            and
            status in ('Status3' , 'Status4')
        )
    )

我有一个这样的DTO:

public class SearchCriteria {

@Embedded
private Filters filters;

@Embeddable
@Getter
@Setter
public static class Filters {
    private List<String> codes;
    private List<TimePeriod> timePeriods;
}

@Embeddable
@Getter
@Setter
public static class TimePeriod {
    private List<String> status;
    private StartDate startDate;
}

@Embeddable
@Getter
@Setter
public static class StartDate {
    private LocalDate from;
    private LocalDate to;
}

对我来说很难。我什么都试过了。我宁愿给你看一个具体的案例，以免产生误解。有人能帮我吗？我将非常感激！

我不需要使用规范，我只需要能够重现那个查询示例，规范似乎是最好的选择。

谢谢大家。

Answer 1

我认为你走在正确的轨道上，标准类看起来很好。下面介绍如何在方法中使用它来构建 JPA 条件，并使用与您的实体对应的存储库执行查询：

public void query(List<String> codes, List<TimePeriod> timePeriods) {
    // build the code filter
    Specification<Table> codeSpec = (root, query, criteriaBuilder) -> {
        Path<String> codeField = root.get("code");
        var codePredicate = criteriaBuilder.in(codeField);
        codes.forEach(code -> codePredicate.value(code));
        return codePredicate;
    };
    // iterate over the time periods
    var timePeriodSpec = timePeriods.stream().map(timePeriod -> {
        Specification<Table> dateSpec = (root, query, criteriaBuilder) -> {
            Path<LocalDate> dateField = root.get("date");
            return criteriaBuilder.between(dateField, timePeriod.startDate.from, timePeriod.startDate.to);
        };
        Specification<Table> statusSpec = (root, query, criteriaBuilder) -> {
            Path<String> statusField = root.get("status");
            var statusPredicate = criteriaBuilder.in(statusField);
            timePeriod.status.forEach(status -> statusPredicate.value(status));
            return statusPredicate;
        };
        // combine the date and status filter
        return dateSpec.and(statusSpec);
    })
    .reduce(Specification::or).get(); // chain the time period filters together
    
    var fullSpec = codeSpec.and(timePeriodSpec);

    var result = tableRepository.findAll(fullSpec, Pageable.unpaged());
}

您还需要确保您的存储库实现了JpaSpecificationExecitor接口，但您可能已经弄清楚了。