Why does Spring Data fail on date queries? - spring

Question

I have records in my mongodb which are like this example record.
{
"_id" : ObjectId("5de6e329bf96cb3f8d253163"),
"changedOn" : ISODate("2019-12-03T22:35:21.126Z"),
"bappid" : "BAPP0131337",
}
I have code which is implemented as:
public List<ChangeEvent> fetchChangeList(Application app, Date from, Date to) {
Criteria criteria = null;
criteria = Criteria.where("bappid").is(app.getBappid());
Query query = Query.query(criteria);
if(from != null && to == null) {
criteria = Criteria.where("changedOn").gte(from);
query.addCriteria(criteria);
}
else if(to != null && from == null) {
criteria = Criteria.where("changedOn").lte(to);
query.addCriteria(criteria);
} else if(from != null && to != null) {
criteria = Criteria.where("changedOn").gte(from).lte(to);
query.addCriteria(criteria);
}
logger.info("Find change list query: {}", query.toString());
List<ChangeEvent> result = mongoOps.find(query, ChangeEvent.class);
return result;
This code always comes up empty. The logging statement generates a log entry like:
Find change list query: Query: { "bappid" : "BAPP0131337", "changedOn" : { "$gte" : { "$date" : 1575418473670 } } }, Fields: { }, Sort: { }
Playing around with variants of the query above in a database which has the record above gets the following results we get.
Returns records:
db["change-events"].find({ "bappid" : "BAPP0131337" }).pretty();
Returns empty set:
db["change-events"].find({ "bappid" : "BAPP0131337", "changedOn" : { "$gte" : { "$date" : 1575418473670 } } }).pretty();
Returns empty set:
db["change-events"].find({ "bappid" : "BAPP0131337", "changedOn" : { "$lte" : { "$date" : 1575418473670 } } }).pretty();
The record returned without the date query should be non empty on one of the two above. But it is empty on both.
What is wrong here?

Answer 1

Since the collection name change-events is different then Class name ChangeEvent so you have to pass the collection name in the find query of mongoOps as below:
List<ChangeEvent> result = mongoOps.find(query, ChangeEvent.class, "change-events");
I have tried it replicating and found that your query without dates in where clause also not working i.e:
Criteria criteria = null;
criteria = Criteria.where("bappid").is(bappid);
Query query = Query.query(criteria);
And the find query on mongoOps as below:
List<ChangeEvent> result = mongoTemplate.find(query, ChangeEvent.class);
Will not work, becuase collection name is missing, below query with collection name execute fine:
List<ChangeEvent> result1 = mongoTemplate.find(query, ChangeEvent.class, "changeEvents");
For details explanation of above discussion you can find out at my Github repo: https://github.com/krishnaiitd/learningJava/blob/master/spring-boot-sample-data-mongodb/src/main/java/sample/data/mongo/main/Application.java#L157