问题描述

实现两个集合的关联并分页查询。
假设：
collection1中有deviceId等字段，collection2 中有deviceId、unitName等字段， 关联这两个colltion，并分页查询

代码实现

    public ResponseEntity<String> getPageList(@RequestBody DevQO qo) {Aggregation aggregation;int pageNo = qo.getPageNo(), pageSize = 2;List<AggregationOperation> operations = new ArrayList<>();if (qo.getDeviceId() != null) {operations.add(Aggregation.match(Criteria.where("deviceId").is(qo.getDeviceId())));}operations.add(Aggregation.lookup("collection2", "deviceId", "deviceId", "collection2"));if (qo.getUnitName() != null) {operations.add(Aggregation.match(Criteria.where("collection2.unitName").is(qo.getUnitName())));}operations.add(Aggregation.sort(Sort.Direction.DESC, "startTime"));operations.add(Aggregation.skip((long) (pageNo - 1) * pageSize));// 跳过之前页面的文档operations.add(Aggregation.limit(pageSize));// 跳过之前页面的文档aggregation = Aggregation.newAggregation(operations);AggregationResults<DeviceStatusInfo> pageData =mongoTemplate.aggregate(aggregation, "alarm_data", DeviceStatusInfo.class);List<DeviceInfo> list = pageData.getMappedResults();JSONObject res = new JSONObject();resJson.put("list", list);return new ResponseEntity<>(JSON.toJSONString(res, SerializerFeature.WriteDateUseDateFormat), HttpStatus.OK);}

返回json

{"list": [{"deviceId": "deviceId","startTime": 1713408948096,"colletion2": {"unitName": "华润北京unitName公司","unitCode": "unitCode",},}]
}

进一步优化代码

在聚合查询结果中将collection2中的unitName，移动到与“startTime”同级的位置，并删除“collection2”字段

    public ResponseEntity<String> getPageList(@RequestBody DevQO qo) {Aggregation aggregation;int pageNo = qo.getPageNo(), pageSize = 2;List<AggregationOperation> operations = new ArrayList<>();if (qo.getDeviceId() != null) {operations.add(Aggregation.match(Criteria.where("deviceId").is(qo.getDeviceId())));}operations.add(Aggregation.lookup("collection2", "deviceId", "deviceId", "collection2"));if (qo.getUnitName() != null) {operations.add(Aggregation.match(Criteria.where("collection2.unitName").is(qo.getUnitName())));}operations.add(Aggregation.project().andInclude("deviceId", "startTime").and("collection2.unitName").as("unitName"));operations.add(Aggregation.sort(Sort.Direction.DESC, "startTime"));operations.add(Aggregation.skip((long) (pageNo - 1) * pageSize));// 跳过之前页面的文档operations.add(Aggregation.limit(pageSize));// 跳过之前页面的文档aggregation = Aggregation.newAggregation(operations);AggregationResults<DeviceStatusInfo> pageData =mongoTemplate.aggregate(aggregation, "alarm_data", DeviceStatusInfo.class);List<DeviceInfo> list = pageData.getMappedResults();JSONObject res = new JSONObject();resJson.put("list", list);return new ResponseEntity<>(JSON.toJSONString(res, SerializerFeature.WriteDateUseDateFormat), HttpStatus.OK);}

返回json

{"list": [{"deviceId": "deviceId","startTime": 1713408948096,"unitName": "华润北京unitName公司"}]
}