MongoDao.java 文件源码

/**
 * 合统计
 *
 * @param collectionName
 * @param match
 * @param sumField
 * @return
 */
public Double sum(String collectionName, Document match, String sumField) {
    AggregateIterable<Document> aggregate = getDB().getCollection(collectionName).aggregate(
            Arrays.asList(
                    match(match)
                    , group(null, Accumulators.sum("_sum", "$" + sumField))
            )
    );
    Document first = aggregate.first();
    if (first != null) {
        return first.getDouble("_sum");
    }
    return null;
}