In spring data mongodb how to achieve pagination for aggregation

Question

In spring data mongodb using mongotemplate or mongorepository, how to achieve pagination for aggregateion

Answer 1

As per the answer https://stackoverflow.com/a/39784851/4546949 I wrote code for Java.

Use aggregation group to get count and array of data with other paging information.

    AggregationOperation group = Aggregation.group().count().as("total")
            .addToSet(pageable.getPageNumber()).as("pageNumber")
            .addToSet(pageable.getPageSize()).as("pageSize")
            .addToSet(pageable.getOffset()).as("offset")
            .push("$$ROOT").as("data");

Use Aggregation project to slice as per the paging information.

    AggregationOperation project = Aggregation.project()
            .andInclude("pageSize", "pageNumber", "total", "offset")
            .and(ArrayOperators.Slice.sliceArrayOf("data").offset((int) pageable.getOffset()).itemCount(pageable.getPageSize()))
            .as("data");

Use mongo template to aggregate.

    Aggregation aggr = newAggregation(group, project);
    CustomPage page = mongoTemplate.aggregate(aggregation, Foo.class, CustomPage.class).getUniqueMappedResult();

Create a CustomPage.

    public class CustomPage {
        private long pageSize;
        private long pageNumber;
        private long offset;
        private long total;
        private List data;
    }