我是MongoDB的新手。我在loginCollection.aggregate
中遇到错误:
类型Mongocollection中的方法汇总(列表)不适用于参数(BasicDBobject)
以下是我的代码段。预先感谢。
public MonthlyLoginCount monthlyLoginCount() {
MonthlyLoginCount monthlyLoginCount = new MonthlyLoginCount();
Map<String, Long> map = new HashMap<String, Long>();
MongoClient mongo = new MongoClient(dataSource, 27017);
MongoCollection<Document> loginCollection = mongo.getDatabase(mongoDataBase).getCollection(loginDetailsCollection);
AggregationOutput logincount = loginCollection.aggregate(new BasicDBObject("$group",
new BasicDBObject("_id", "$email_id").append("value", new BasicDBObject("$push", "$value"))));
Iterator<DBObject> results = logincount.results().iterator();
while (results.hasNext()) {
try {
Object str = results.next().get("_id");
long count = loginCollection.count(new BasicDBObject("email_id", str.toString()));
System.out.println("email id:: " + str.toString() + " count: " + count);
map.put(str.toString(), count);
} catch (Exception e) {
e.printStackTrace();
}
}
mongo.close();
monthlyLoginCount.setMap(map);
return monthlyLoginCount;
}
回答此问题有点棘手
自2.x火车中的某个时候,aggregate()
方法已接受List
。例如:
// in 2.14
AggregationOutput aggregate(List<DBObject> pipeline)
// in 3.x
AggregateIterable<TDocument> aggregate(List<? extends Bson> pipeline);
唯一的参数是List
,此列表表示聚合管道中的阶段。例如:
AggregateIterable<Document> documents = collection.aggregate(Arrays.asList(
new Document("$match", theMatchDocument),
new Document("$project", theProjectionDocument)
));
您的问题中包含的异常消息:
"类型Mongocollection中的方法汇总(列表)不适用于参数(BasicDBobject)"
...意味着您正在尝试致电aggregate(List)
,并且将其分配给AggregationOutput
使我怀疑您正在使用v2.1x(请参阅API文档。重述如下:
AggregationOutput logincount = loginCollection.aggregate(Arrays.asList(
new BasicDBObject("$group", new BasicDBObject("_id", "$email_id").append("value", new BasicDBObject("$push", "$value")))
));