project :控制返回的字段,例如一个实体类,我们只需要部分字段
1 插入数据
mongoTemplate.save(new Role("zhang1",5));
mongoTemplate.save(new Role("zhang2",6));
mongoTemplate.save(new Role("zhang3",12));
mongoTemplate.save(new Role("zhang4",14));
mongoTemplate.save(new Role("zhang5",23));
2 查询
TypedAggregation<Role> agg = Aggregation.newAggregation(Role.class,Aggregation.match(Criteria.where("name").is("zhang1")),
Aggregation.count().as("count1"),
Aggregation.project("count1"));
AggregationResults<Document> result = mongoTemplate.aggregate(agg,Document.class);
result.getMappedResults().forEach(document -> System.out.println(document));
3 结果
Document{{count1=1}}
4 注意:
这里多个Aggregation 是按先后顺序执行的,顺序不一致可能会报错