I want to save the server’s response in database (class Parent). The json has nested object, which also should be saved in database in new table (class Nested). The problem is what I don’t know how to write class Parent and ParentDao to make it use NestedDao
#Entity
data class Parent(
#PrimaryKey(autoGenerate = true)
var id: Long? = null,
#SerializedName(«nested»)
val homeTeam: Nested,
//other fields
)
#Entity
data class Nested(
#PrimaryKey(autoGenerate = true)
var nestedId: Long? = null,
#SerializedName("name")
val name: String,
//other fields
)
#Dao
interface ParentDao {
#Query("SELECT * FROM parent»)
fun getData(): Single<List<Parent>>
#Insert
fun insert(matches: List<Parent>)
}
This gives me an error: Cannot figure out how to save this field into database. You can consider adding a type converter for it.
So, what should I do to save and query Parent with Nested at once?
I don't know if you've succeed or not, but here is my answer I hope it'll help you.
That's what I used for my project and what is recommended for Room in Android docs
#Entity
data class Parent(
#PrimaryKey(autoGenerate = true)
var id: Long? = null,
#Embedded #ColumnInfo(name= "nested")
val homeTeam: Nested,
//other fields
)
data class Nested(
#PrimaryKey(autoGenerate = true)
var nestedId: Long? = null,
#ColumnInfo(name= "name")
val name: String,
//other fields
)
#Dao
interface ParentDao {
#Query("SELECT * FROM parent»)
fun getData(): Single<List<Parent>>
#Insert
fun insert(matches: List<Parent>)
}
Related
I have tried this several ways (U can assume my MongoConfiguration is Correct)
Using implementation 'org.springframework.boot:spring-boot-starter-data-mongodb:2.5.3'
My Class
#Document(collection = "address")
class Address {
#Id
var id: String? = null
var label: String? = null
var number: String? = null
var street: String? = null
...
My Repository
#Repository
interface AddressRepository : MongoRepository<Address, String> {
fun findByLabel(label: String): Address
}
in My #RestController I call the save (or insert)
val savedAddress = addressRepository.insert(address)
According to Gradle: org.springframework.data:spring-data-mongodb:3.1.6 as well as Gradle: org.springframework.data:spring-data-commons:2.4.6 Docs
Returns: the saved entity; will never be null.
However It does create a record! I inspected the result by using Compass
But it only echoes the address content I used to create it! witout the ID
If I would query the record e.g.
returnedAddress= savedAddress.label?.let { addressRepository.findByLabel(it) }!!
I get the rocord returned WITH the Id!
This Behavior I detected some time now and it is not always possible to locate the correct record again if the Id is the only Unique key in the collection!
Is there a Mistake?, configuration or any other way I can get the ObjectId / _id emmitted properly
Note: <S extends T> S save(S entity) calls insert when the entity record is new
I have two collections called persons and addresses. The idea is to have person hold an address in the field address. I use Spring Data MongoDB to persist those mentioned documents.
My usual way of crafting the "relation" between Person > Address was to store the ID of the address and give it to the person object. Later when I find() a person I resolve the address object by it's id and voila I have my person + address.
However I find this somewhat every cumbersome since in my code I just want to add the Address object as whole and not only it's ID so I can work with it while also saving it to the repository at any point of time.
I therefore started a little unit test to see how Spring Data MongoDB saves the Address object if it's just a field of Person and is not saved by it's own Repository.
This is what I came up with:
import org.springframework.data.mongodb.core.mapping.Document
import org.springframework.data.mongodb.repository.MongoRepository
import org.springframework.stereotype.Repository
#Document("person")
data class Person(
val id: String,
val name: String,
val age: Int,
var address: Address
)
#Document("addresses")
data class Address(
val id: String,
val street: String?,
val number: Int?
)
#Repository
interface PersonRepository : MongoRepository<Person, String>
#Repository
interface AddressRepository : MongoRepository<Address, String>
And this is the unit test - that fails with the last steps as I was expecting:
internal class FooTest #Autowired constructor(
private val personRepository: PersonRepository,
private val addressRepository: AddressRepository
) {
#Test
fun `some experiment`() {
val testPerson = Person("001", "Peter", 25, Address("011","Lumberbumber", 12))
personRepository.save(testPerson)
val person = personRepository.findAll()[0]
assertThat(person).isNotNull
assertThat(person.address).isNotNull
assertThat(person.address.street).isEqualTo("Lumberbumber")
assertThat(person.address.number).isEqualTo(12)
// works because address was just copied into the object structure
// of `person` and was not seen as a standalone document
val address = addressRepository.findAll()[0]
assertThat(address.street).isEqualTo("Lumberbumber") // fails
assertThat(address.number).isEqualTo(12) // fails
// As expected `address` was not persisted alongside the `person` document.
}
}
So I thought about using AbstractMongoEventListener<Person> to intercept the saving process and pick the Address object out from Person here and do a addressRepository.save(addressDocument) while putting a lightweight address object (only having the ID) back in the Person document.
The same I'd to in the reverse when doing a find for Person and assembling Person and Address together again.
#Component
class MongoSaveInterceptor(
val addressRepository: AddressRepository
) : AbstractMongoEventListener<Person>() {
override fun onBeforeConvert(event: BeforeConvertEvent<Person>) {
val personToSave = event.source
val extractedAddress = personToSave.address
val idOfAddress = addressRepository.save(extractedAddress).id
personToSave.address = Address(idOfAddress, null, null)
}
override fun onAfterConvert(event: AfterConvertEvent<Person>) {
val person = event.source
val idOfAddress = person.address.id
val foundAddress = addressRepository.findById(idOfAddress)
foundAddress.ifPresent {
person.address = it
}
}
}
It works that way and might be a workaround solution for my requirement.
BUT
I feel that there has to be something like that already working and I might just need to find the proper configuration for that.
That's where I am stuck atm and need some guidance.
Another research showed me it's about #DBRef (https://www.baeldung.com/cascading-with-dbref-and-lifecycle-events-in-spring-data-mongodb) I have to use. This way Spring Data MongoDB stores the embedded document class and resolves it when loading the parent document object from the database.
I'm new to ROOM library. I've some complex json data structure which i would like to store in ROOM database, i don't know how to use Type convertes for multiple list of objectes. Following are my Entities,
// Trying to put all my custom models in a single table
#Entity(tableName = "myTable")
data class RaceModelDatabase(
#PrimaryKey
val ID: String,
#Embedded val info: CustomModel,
#Embedded(prefix = "parti")
val parti: Map<String,UserModelDatabase> ,
#Embedded val totalTime: Map<String,TimeDataModel>
)
// Custom Models which also has Map objects
data class CustomModel (val name :String, val crdate : String )
data class UserModelDatabase(#Embedded val info : CustomModel,
#Embedded(prefix = "Result_") val result :Map<String,CustomModel>
)
data class TimeDataModel (
val Start : Long,
val End : Long
)
Here is an example of how to use TypeAdapter for one of your Map objects. You could follow the same for the rest.
class RaceTypeConverter {
#JvmStatic
#TypeConverter
fun fromString(value: String): Map<String, TimeDataModel > {
val mapType = object : TypeToken<Map<String, TimeDataModel >>() {}.type
return Gson().fromJson(value, mapType)
}
#TypeConverter
#JvmStatic
fun fromStringMap(map: Map<String, TimeDataModel>): String {
val gson = Gson()
return gson.toJson(map)
}
}
I read that specifying optional = false in the #ManyToOne association annotation could help Spring improve the performance of the queries.
In a Kotlin data class entity, do I actually need to specify the parameter in the annotation, or can Spring figure this out by itself using the nullability of the item field?
For instance, if I have the following declaration:
#Entity
#Table(name = ACCESS_LOGS_ARCHIVES_TABLE, indexes = [
Index(name = "access_logs_archives_item_idx", columnList = "access_item_id")
])
data class AccessLogArchive(
val date: LocalDate,
#ManyToOne(optional = false)
#JoinColumn(name = "access_item_id", nullable = false)
val item: AccessLogItem,
val occurrences: Int
) {
#Id
#GeneratedValue
var id: Long? = null
}
#Entity
#Table(name = ACCESS_ITEMS_TABLE)
data class AccessLogItem(
#Column(length = 3) val code: String,
#Column(columnDefinition = "text") val path: String,
#Column(length = 10) val verb: String
) {
#Id
#GeneratedValue
var id: Long? = null
}
In this case, I would for instance expect Spring to know that the item field is not nullable, and thus the relationship should be understood as optional=false even without specifying it as I did. Is this the case?
Same question goes for the #JoinColumn's nullable = false, by the way.
Consider a simple entity like a Room which has a #ManyToOne relationship to House.
#Entity
class Room(
#ManyToOne(optional = true)
val house: House
) {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
val id: Long = 0
}
JPA will create a room table with a column
`house_id` bigint(20) DEFAULT NULL
If you specify #ManyToOne(optional = false)
the column will look like this:
`house_id` bigint(20) NOT NULL
By specifiying optional you tell JPA how the schema should be generated, whether the column can be NULL or not.
At runtime trying to load a Room without a House will cause an Exception if the house property is not nullable (House instead of House?) even when value of optional is true.
The same applies to #JoinColumn.
Is #ManyToOne's “optional” param automatically set using Kotlin's
nullability?
No it is not. It is independent from that and by default set to true.
Conclusion: In order for you schema to reflect your entities it is a good idea to use optional = true if the house property would be nullable and optional = false if the house property would be non-nullable.
I have a collection, with documents having a field named _id of type String, not generated manually.
I have been trying to get a document using its id.
val criteria = Criteria.where("_id").`is`("a2z3e44R")
val document = mongoTemplate.findOne(Query.query(criteria), MyDocument::class.java) // returns null
val criteria = Criteria.where("_id").`is`(ObjectId("a2z3e44R"))
val document = mongoTemplate.findOne(Query.query(criteria), MyDocument::class.java) // returns null
val document = mongoTemplate.findById("a2z3e44R", MyDocument::class.java) // returns null
mongoTemplate.findAll(MyDocument::class.java).first { myDocument ->
myDocument._id == "a2z3e44R"
} // OK...
MyDocument is
data class MyDocument(val _id: String, val name: String)
Trying to find a document by another field works.
An idea of what I could be missing or a workaround?
You should indicate the type of the id like this
public class Article {
#MongoId(value = FieldType.OBJECT_ID)
private String id;
private String title;
private String desc;
}
Try mark _id with annotation #Id. The #Id annotation is used to specify the identifier for Spring.
data class MyDocument(#Id val _id: String, val name: String)
Ypu could define in your repository:
public interface MyDocumentRepository extends MongoRepository<MyDocument, String> {
Pets findBy_id(ObjectId _id);
}
and use it :
myDocumentRepository.findBy_id("a2z3e44R");
for more info see
or
ObjectId objID = new ObjectId("a2z3e44R");
query.addCriteria(Criteria.where("_id").lt(objID));
like this other answer link