集合为空时Spring数据mongodb计数错误

这两个问题之间有什么区别

当集合上存在或不存在值时，此查询工作正常

@Query(value = "{'request.req_number':?0, 'product.prod_number':?1}", count = true)
int myMethod(String requestNumber, String productNumber){...

但当集合为空时，这将导致空指针

    @Aggregation(pipeline = {"{'$match':{'request.req_number':?0, 'product.prod_number':?1} }","{'$count':'total'}"}) 
int myMethod(String requestNumber, String productNumber){...

java.lang.NullPointerException:null 在org.springframework.data.mongodb.repository.query.AggregationUtils.extractSimpleTypeResult（AggregationUtils.java:192）~[spring-data-mongodb-2.2.1.RELEASE.jar:2.2.1.RELEASE]

---

在org.springframework.data.mongodb.repository.query.StringBasedAggregation.doExecute（StringBasedAggregation.java:114）~[spring-data-mongodb-2.2.1.RELEASE.jar:2.2.1.RELEASE]

聚合返回“对象”，您应该使用类似这样的内容：

@Data
@AllArgsConstructor
class Count {
    Long total;
}
...
@Aggregation(pipeline = {"{'$match':{'request.req_number':?0, 'product.prod_number':?1} }","{'$count':'total'}"}) 
Count myMethod(String requestNumber, String productNumber){...