spring-boot - 在spring data mongodb中如何实现分页进行聚合

Question

spring data mongodb中使用mongotemplate或mongorepository，如何实现分页进行聚合

Answer 1

这是我的通用解决方案:

public Page<ResultObject> list(Pageable pageable) {
    // build your main stages
    List<AggregationOperation> mainStages = Arrays.asList(match(....), group(....));
    return pageAggregation(pageable, mainStages, "target-collection", ResultObject.class);
}

public <T> Page<T> pageAggregation(
        final Pageable pageable,
        final List<AggregationOperation> mainStages,
        final String collection,
        final Class<T> clazz) {
    final List<AggregationOperation> stagesWithCount = new ArrayList<>(mainStages);
    stagesWithCount.add(count().as("count"));
    final Aggregation countAgg = newAggregation(stagesWithCount);
    final Long count = Optional
            .ofNullable(mongoTemplate.aggregate(countAgg, collection, Document.class).getUniqueMappedResult())
            .map(doc -> ((Integer) doc.get("count")).longValue())
            .orElse(0L);

    final List<AggregationOperation> stagesWithPaging = new ArrayList<>(mainStages);
    stagesWithPaging.add(sort(pageable.getSort()));
    stagesWithPaging.add(skip(pageable.getOffset()));
    stagesWithPaging.add(limit(pageable.getPageSize()));
    final Aggregation resultAgg = newAggregation(stagesWithPaging);
    final List<T> result = mongoTemplate.aggregate(resultAgg, collection, clazz).getMappedResults();

    return new PageImpl<>(result, pageable, count);
}