I'm having a duplicate query when performing a simple query. The files:
SomeClass.java:
#Document(collection = "someCollection")
public class SomeClass {
private String _id;
private String someField;
//...
}
SomeClassRepository.java:
#Repository
public interface SomeClassRepository extends MongoRepository<SomeClass, String> {
}
Service.java:
#Autowired
private SomeClassRepository someClassRepository;
public SomeClass find(String id){
return someClassRepository.findOne(id);
}
application.properties:
logging.level.org.springframework.data.mongodb.core.MongoTemplate=DEBUG
Log file:
14:14:46.514 [qtp1658534033-19] DEBUG o.s.data.mongodb.core.MongoTemplate - findOne using query: { "_id" : "40c23743-afdb-45ca-9231-c467f8e8b320"} fields: null for class: class com.somepackage.SomeClass in collection: someCollection
14:14:46.534 [qtp1658534033-19] DEBUG o.s.data.mongodb.core.MongoTemplate - findOne using query: { "_id" : "40c23743-afdb-45ca-9231-c467f8e8b320"} in db.collection: someDatabase.someCollection
I also tried to:
1) use #Id annotation with a field named "someId"
2) use #Id annotation with a field named "id"
3) use a field named "id" (without #Id annotation)
Unfortunately, I always have two queries to the database.
Anyone knows how to perform a single query?
Thanks!
Its only single query that is sent to database. Your log messages are coming from two different places.
First place : doFindOne method - link; Second place :
FindOneCallback class - link
You can also confirm the logs by looking at db logs. More info here
Related
I am using Spring data mongo with azure cosmos. My structure looks like below.
I have an Id field in my collection that is not annotated with #Id. I see both _id and id are in the DB but When I retrieve id field comes with the value is in _id.
#Document(collection = "mycollection")
class MyObject{
private String id;
...
}
public interface MyRepository extends MongoRepository<MyObject, Void> {
}
Used #Field("id") to tell spring data threat this field as is not as _id/pk field for mongo
I'm trying to implement a rest api using RepositoryRestResource and RestTemplate
It all works rather well, except for loading #DBRef's
Consider this data model:
public class Order
{
#Id
String id;
#DBRef
Customer customer;
... other stuff
}
public class Customer
{
#Id
String id;
String name;
...
}
And the following repository (similar one for customer)
#RepositoryRestResource(excerptProjection = OrderSummary.class)
public interface OrderRestRepository extends MongoRepositor<Order,String>{}
The rest api returns the following JSON:
{
"id" : 4,
**other stuff**,
"_links" : {
"self" : {
"href" : "http://localhost:12345/api/orders/4"
},
"customer" : {
"href" : "http://localhost:12345/api/orders/4/customer"
}
}
}
Which if loaded correctly by the resttemplate will create a new Order instance with customer = null
Is it possible to eagerly resolve the customer on the repository end and embed the JSON?
Eagerly resolving dependent entities in this case will raise most probably N+1 database access problem.
I don't think there is a way to do that using default Spring Data REST/Mongo repositories implementation.
Here are some alternatives:
Construct an own custom #RestController method that would access the database and construct desired output
Use Projections to populate fields from related collection, e.g.
#Projection(name = "main", types = Order.class)
public interface OrderProjection {
...
// either
#Value("#{customerRepository.findById(target.customerId)}")
Customer getCustomer();
// or
#Value("#{customerService.getById(target.customerId)}")
Customer getCustomer();
// or
CustomerProjection getCustomer();
}
#Projection(name = "main", types = Customer.class)
public interface CustomerProjection {
...
}
The customerService.getById can employ caching (e.g. using Spring #Cachable annotation) to mitigate the performance penalty of accessing the database additionally for each result set record.
Add redundancy to your data model and store copies of the Customer object fields in the Order collection on creation/update.
This kind of problem arises, in my opinion, because MongoDB doesn't support joining different document collections very well (its "$lookup" operator has significant limitations in comparison to the common SQL JOINs).
MongoDB docs also do not recommend using #DBRef fields unless joining collections hosted in distinct servers:
Unless you have a compelling reason to use DBRefs, use manual references instead.
Here's also a similar question.
I have a collection of entities that look like this:
public class ClientEntity {
#Id
private String id;
#Indexed(unique = true)
private String clientId;
private String name;
#DBRef
private List<ClientMachineEntity> machines;
...
}
...where ClientMachineEntity looks like:
public class ClientMachineEntity {
#Id
private String id;
#Indexed(unique = true)
private String clientMachineId;
private String hostName;
...
}
I have a working search that finds ClientEntities by matching against "clientId" and "name":
public List<ClientEntity> searchByIdAndName(String id, String name) {
Criteria idCriteria = Criteria.where("clientId").regex(id, "i");
Criteria nameCriteria = Criteria.where("name").regex(name, "i");
Query query = new Query(new Criteria().orOperator(idCriteria, nameCriteria));
...
}
So my question is, how can I expand this search so that it also matches against "clientMachineId" in the list of sub-entities? I tried adding the following criteria:
Criteria machineCriteria = Criteria.where("machines.clientMachineId").regex(id, "i");
...but that doesn't work, presumably because machines is a LIST of entities, not just a single sub-entity.
UPDATE: It seems like what I'm looking for is the .elemMatch() functionality, but when I try that:
Criteria machineCriteria = Criteria.where("machines").elemMatch(Criteria.where("clientMachineId").regex(id, "i"));
...I get the following error:
org.springframework.data.mapping.model.MappingException: No mapping metadata found for class com.mongodb.BasicDBObject
You can't query by fields in subentities linked with DBRef. If ClientMachineEntity would be embedded in ClientMachine - then you could use dot notation or $elemMatch depending on needs.
In your particular example - couldn't field ClientMachineEntity.clientMachineId be saved as _id and used as a primary key? Then you could get the results you need - take a look at: How to query mongodb with DBRef
My suggestion for development with Spring Data MongoDB is - first learn how to (and if it's possible) do it in plain Javascript with MongoDB console, then learn how to do the same with Spring Data MongoDB.
I have a class hierarchy designed for store user notifications:
#Document
public class Notification<T> {
#Id
private String id;
#DBRef
private T tag;
...
}
#Document
public class NotificationA extends Notification<WrappedA> {
}
#Document
public class NotificationB extends Notification<WrappedB> {
}
...
This is useful for returning polymorphic arrays, allowing me to store any kind of data in the "tag" field. The problem starts when the wrapped objects contains #DBRef fields:
#Document
public class WrappedA {
#Id
private String id;
#DBRef
private JetAnotherClass referenced;
...
}
Queries on the fields of "tag" works fine:
db.NotificationA.find( {"tag.$id": ObjectId("507b9902...32a")} )
But I need to query on the fields of JetAnotherClass (two levels of #DBRef fields). I've tried with dot notation and also with subobjects but it returns null:
Dot notation:
db.NotificationA.findOne( {"tag.$referenced.$id": ObjectId("508a7701...29f")} )
Subobjects:
db.NotificationA.findOne( {"tag.$referenced": { "_id": ObjectId("508a7701...29f") }} )
Any help?
Thanks in advance!
Since you look like you are only querying by _id I believe you can do:
db.NotificationA.findOne({"tag.$id": ObjectId("blah")});
However:
But I need to query on the fields of JetAnotherClass (two levels of #DBRef fields).
DBRefs are not JOINs, they are merely a self describing _id in the event that you do not know the linking collection it will create a helper object so you don't have to code this yourself on the client side.
You can find more on DBRefs here: http://docs.mongodb.org/manual/applications/database-references/
Basically you can query the sub fields within the DBRef from the same document, i.e.: DBRef.$_id but you cannot, server-side, resolve that DBRef and query on the resulting fields.
I have two domain objects,
#Document
public class PracticeQuestion {
private int userId;
private List<Question> questions;
// Getters and setters
}
#Document
public class Question {
private int questionID;
private String type;
// Getters and setters
}
My JSON doc is like this,
{
"_id" : ObjectId("506d9c0ce4b005cb478c2e97"),
"userId" : 1,
"questions" : [
{
"questionID" : 1,
"type" : "optional"
},
{
"questionID" : 3,
"type" : "mandatory"
}
]
}
I have to update the "type" based on userId and questionId, so I have written a findBy query method inside the custom Repository interface,
public interface CustomRepository extends MongoRepository<PracticeQuestion, String> {
List<PracticeQuestion> findByUserIdAndQuestionsQuestionID(int userId,int questionID);
}
My problem is when I execute this method with userId as 1 and questionID as 3, it returns the entire questions list irrespective of the questionID. Is the query method name valid or how should I write the query for nested objects.
Thanks for any suggestion.
Just use the #Query annotation on that method.
public interface CustomRepository extends MongoRepository<PracticeQuestion, String> {
#Query(value = "{ 'userId' : ?0, 'questions.questionID' : ?1 }", fields = "{ 'questions.questionID' : 1 }")
List<PracticeQuestion> findByUserIdAndQuestionsQuestionID(int userId, int questionID);
}
By adding the fields part of the #Query annotation, you are telling Mongo to only return that part of the document. Beware though, it still returns the entire document in the same format - just missing everything you did not specify. So your code will still have to return List<PracticeQuestion> and you will have to do:
foreach (PracticeQuestion pq : practiceQuestions) {
Question q = pq.getQuestions().get(0); // This should be your question.
}
Property expressions
Property expressions can refer only to a direct property of the managed entity, as shown in the preceding example. At query creation time you already make sure that the parsed property is a property of the managed domain class. However, you can also define constraints by traversing nested properties. Assume Persons have Addresses with ZipCodes. In that case a method name of List<Person> findByAddressZipCode(ZipCode zipCode);
creates the property traversal x.address.zipCode. The resolution algorithm starts with interpreting the entire part (AddressZipCode) as the property and checks the domain class for a property with that name (uncapitalized). If the algorithm succeeds it uses that property. If not, the algorithm splits up the source at the camel case parts from the right side into a head and a tail and tries to find the corresponding property, in our example, AddressZip and Code. If the algorithm finds a property with that head it takes the tail and continue building the tree down from there, splitting the tail up in the way just described. If the first split does not match, the algorithm move the split point to the left (Address, ZipCode) and continues.
Although this should work for most cases, it is possible for the algorithm to select the wrong property. Suppose the Person class has an addressZip property as well. The algorithm would match in the first split round already and essentially choose the wrong property and finally fail (as the type of addressZip probably has no code property). To resolve this ambiguity you can use _ inside your method name to manually define traversal points. So our method name would end up like so:
UserDataRepository:
List<UserData> findByAddress_ZipCode(ZipCode zipCode);
UserData findByUserId(String userId);
ProfileRepository:
Profile findByProfileId(String profileId);
UserDataRepositoryImpl:
UserData userData = userDateRepository.findByUserId(userId);
Profile profile = profileRepository.findByProfileId(userData.getProfileId());
userData.setProfile(profile);
Sample Pojo :
public class UserData {
private String userId;
private String status;
private Address address;
private String profileId;
//New Property
private Profile profile;
//TODO:setter & getter
}
public class Profile {
private String email;
private String profileId;
}
For the above Document/POJO in your Repository Class:
UserData findByProfile_Email(String email);
For ref : http://docs.spring.io/spring-data/data-commons/docs/1.6.1.RELEASE/reference/html/repositories.html
You need to use Mongo Aggregation framework :
1) Create custom method for mongo repository : Add custom method to Repository
UnwindOperation unwind = Aggregation.unwind("questions");
MatchOperation match = Aggregation.match(Criteria.where("userId").is(userId).and("questions.questionId").is(questionID));
Aggregation aggregation = Aggregation.newAggregation(unwind,match);
AggregationResults<PracticeQuestionUnwind> results = mongoOperations.aggregate(aggregation, "PracticeQuestion",
PracticeQuestionUnwind.class);
return results.getMappedResults();
2) You need to cretae a class(Because unwind operation has changed the class structure) like below :
public class PracticeQuestionUnwind {
private String userId;
private Question questions;
This will give you only those result which matches the provide userId and questionId
Result for userId: 1 and questionId : 111 :
{
"userId": "1",
"questions": {
"questionId": "111",
"type": "optional"
}
}
i too had similar issue. for that i added $ before the nested class attributes.
try below query
#Query(value = "{ 'userId' : ?0, 'questions.$questionID' : ?1 }") List<PracticeQuestion> findPracticeQuestionByUserIdAndQuestionsQuestionID(int userId, int questionID);