I recently discovered the method copyProperties from BeanUBeanUtilstils class and I was wondering how can I copy the properties of a class into a new empty class? for example:
data class User(val name: String, age: Int)
data class ConvertedUser(val name: String, age: Int, address: String)
I already have a class User with the properties filled and I want to create a new class ConvertedUser using the copyProperties but I can't instantiate a new ConvertedUser without passing the parameters to the constructor.
import org.springframework.beans.BeanUtils
val user = User("name", 1)
val cUser = ConvertedUser() // No value passed for parameter name, age and address.
BeanUtils.copyProperties(user, cUser)
Is it possible to copy properties from an existing class to a new "empty" class?
Related
I'm looking for a better way to change a model with Spring + Mongodb, currently every time a property is added to a model, we have to create a command to be ran in mongosh to add that field to all documents, and then save it so that it can be ran on every environment that the new model is pushed to.
So for example, lets say a Event object has the properties:
#Document
data class Device(
#Id
val id: String? = null,
#Indexed(unique = true)
val name: String,
var location: String,
)
And we want to add a field "date": 2023-02-02T20:10:19.111Z to it. Currently I will have to create a mongosh command to update all events on the collection to add that field, so something like this:
db.device.updateMany({}, {$set: {'date': new Date().toISOString()}})
We then save this, and remember to run it every single time we merge to a upstream branch.
Is there a better way to define a new model with the date, so that it can create the field automatically?
I would add the new property with a default value, but everyone usecase/trade-offs is different.
#Document
data class Device(
#Id
val id: String? = null,
#Indexed(unique = true)
val name: String,
var location: String,
val newProperty:String? = null
)
This will allow you to get values don't exist in the database as null
I am working on Kotlin + SpringBoot web service, in which I want to transform DTOs into entities in the most convenient way.
Entities:
#Entity
data class Shop(
#Id
#GeneratedValue
val id: Long,
val name: String
#OneToOne
val owner: User,
...
)
#Entity
data class User(
#Id
#GeneratedValue
val id: Long,
val name: String,
...
)
DTO:
data class ShopDTO(
val id: Long,
val name: String,
val ownerId: Long,
val ownerName: String,
...
)
So when someone wants to create a new Shop, my service gets a ShopDTO(name, ownerId) as request body, then I need to transform it into Shop object to be able to save it to the DB. Now here is how my mapper function looks like:
fun fromDTO(source: ShopDTO) = Shop(
id = source.id,
name = source.name,
owner = ???,
...
)
To be able to store a Shop with an owner I only need an id. It would be enough to create a new User with the given ownerId.
To achive this I tried these solutions:
Add default value to the fields in the User class.
Make the fields nullable.
Add a secondary constructor. This also needs default values.
Use some reflection magic to create an empty object and then set the id.
Call a findById method on the UserRepository with the given id.
I want to keep the non-null, immutable fields of my entities and do not want to use reflection. Also do not want to run an unnecessary select DB query just to get back the user by the id.
Could you please suggest me other options? How would you handle this situation? Is there any good mapper framework in Kotlin which can solve this problem?
Firstly, your question says you want to do entity -> DTO, but actually you want to do DTO -> entity, so you should clear that up.
Secondly, you are getting the shop name and owner Id in the ShopDTO. But you are assigning the owner Id to the shop Id in the your fromDTO(source: ShopDTO) function. Changing it up would be sufficient.
fun fromDTO(source: ShopDTO) = Shop(
name = source.name,
owner = ownerRepo.findById(source.ownerId)
)
Obviously, if you're using JPA, then you have to make a DB call to get the owner first. If your business logic doesn't ensure that a User with that Id exists, then you could write a method like this to make a user.
fun getOrCreateUser(ownerId: Long) =
ownerRepo.findUserById(ownerId) ?: User(
id = ownerId,
name = "Some random DefaultName"
).run(ownerRepo::save)
This would get a User by the Id if it exists, or create a new user with some generic name.
Do let me know if this solves your issue!
I'm trying to deserialize a complex GET request into a structure of nested objects.
The GET requests looks like:
curl 'localhost:8080/?id=1&inner.id=1'
and the code should look like this:
class RootObj(val id: Int, inner: InnerObject)
class InnerObject(val id: Int)
#RestController
class SearchController {
#GetMapping(path = ["/"])
fun getRoot(rootObj: RootObj): String {
return "ok"
}
}
This doesn't work out of the box I guess because spring doesn't know how properly create this nested structure.
Parameter specified as non-null is null: [...] parameter inner","path":"/"}%
Is there a way to overcome this problem? Maybe providing a totally custom deserializer code?
As alternative solution, I guess I could flatten the object hierarchy but for doing so I must be able to map a query parameter like inner.id to a field named innerId
Spring can actually map the query params to the custom object directly, but you need to provide defaults to the params of the custom object constructor.
So you need to define your classes as below for it to work
class RootObj(val id: Int = 0, val inner: InnerObject = InnerObject(0))
class InnerObject(var id: Int = 0)
Do note that the id field of InnerObject would have to be declared as var for Spring to be able to map it. Then curl 'localhost:8080/?id=1&inner.id=1' would work fine.
I am new to django and faced to several problems trying to write a simple service.
What am I trying to do?
I intend to write a generic crud service for my models using rest-framework library.
I don't want to write serializers and views to all my models and trying to optimize code and learn some useful stuff.
My model
Let's imagine I have an abstract BaseBusinessObject
class BaseBusinessObject(models.Model):
CreatedAt = models.DateField()
UpdatedAt = models.DateField()
class Meta:
abstract = True
I also have a plenty of concrete classes, which are inherited from base one:
class Product(BaseBusinessObject):
Description: models.TextField()
Type: models.CharField()
....
class Company(BaseBusinessObject):
Title: models.CharField()
....
class Person(BaseBusinessObject):
Name: models.CharField()
and so on
What I want
I already figured out, that with rest-framework I can create serializers and views, then register router for url .../Product, .../Company, .../Person. But what if I have 1000 classes? This is boring
A. How can I dynamically specified url's for child objects? I don't want to hardcode methods, I am looking for solution...something like this:
.../api/Entities/ClassName
B. How can I then use my dynamically created urls in django-rest-framework?
router.register('persons', PersonViewSet)
How can write it in more generic way?
router.register('<ClassName>', <GenericViewSet>)
C. Using DRF I can create my viewset for each concrete class in my model:
class PersonViewSet(viewsets.ModelViewSet):
queryset = Person.objects.all()
serializer_class = PersonSerializer
But as I said I have a lot of classes. How can I write it in more generic way?
I tried to create a view set for abstract class, but there are some trouble when querying an abstract object.
Is it possible to create such service for an abstract class and then all its child simply(or not simply) inherit CRUD methods?
Maybe I should try to write a factory for serializers and viewsets?
What possible solutions could I implement for solving my problem?
After 2 days of walking around I finally find my solution. May be someone else will face the some problem, so I trying to explain what I had already done.
First, I create a "base" application inside my django project and add it to settings.py. Then I create an abstract class in models.py:
class BaseCrudEntity(models.Model):
pass
class Meta:
abstract = True
I want to write a generic service for CRUD operations for all "business" classes.
The problem is that I don't want to write serializers and views for them - I want to create them "on fly", dynamically. I decided to use django rest framework as well, because I am not intended to create a bycicle again.
I decided to inherit all my "business" classes from that abstract one and write a service for all possible "families"
So I have to create a fabric which is responsible for VeiwSet creation.
Here is my view.py:
class BaseCrudViewSetFabric():
#classmethod
def CreateViewSet(self, _context):
classname = _context.__name__ + 'ViewSet'
return type(classname, (viewsets.ModelViewSet,), {
'queryset':_context.objects.all(),
'serializer_class':BaseCrudSerializerFabric.CreateSrializer(_context)
})
pass
here _context - variable which describes concrete class of my model.
as you can see this function creates a concrete ViewSet based on my context. Inside it a Serializers fabric is called.
Here the code of my serializers.py:
class BaseCrudSerializerFabric():
#classmethod
def CreateSrializer(self, _context):
classname = _context.__name__
_Meta = type('Meta', (), {'model':_context,'fields':'__all__'})
_crudserializer = type(
classname,
(serializers.ModelSerializer,),
{'Meta': _Meta}
)
return _crudserializer
Moreover, I have to write a service for dynamically routing - I don't wanna hardcode my urls.
Here the example ursl.py from core project:
from base.urls import router
url(r'^api/v1/', include(router.urls))
and from base/urls.py:
from rest_framework.routers import DefaultRouter, SimpleRouter
from base.models.BaseCrudEntity import BaseCrudEntity
from base.views.basecrud_view import BaseCrudViewSetFabric
class CustomRouter(SimpleRouter):
def RoutRegister(self):
childs = getChilds(BaseCrudEntity)
#print(childs)
for ch in childs:
if (ch._meta.abstract == False):
#print(ch.__name__)
prefix = ch.__name__
self.register(prefix, BaseCrudViewSetFabric.CreateViewSet(ch))
return(self)
pass
router = CustomRouter()
router.RoutRegister()
Finally I simply create some concrete models:
from django.db import models
from base.models.BaseCrudEntity import BaseCrudEntity
class Person(BaseCrudEntity):
Name = models.CharField(max_length = 255)
Surname = models.CharField(max_length = 255)
Patronymic = models.CharField(max_length = 255, null = True)
DateOfBirth = models.DateField(null = True)
#slug = models.SlugField(default = 'hui', editable = False)
def __str__(self):
return "{} {} {}".format (self.Surname, self.Name, self.Patronymic)
and thats all.
When application starts it register a route for http://127.0.0.1:8000/api/v1/Person and creates serializers and viewsets so all CRUD operations provided by Django- Rest Framework will be provided as well.
I would suggest using query parameters instead of path parameters, then you just register one URL and process the various elements of the request and route it correctly server-side. When do I use path params vs. query params in a RESTful API?
As per docs, kotlin var properties can be bind in ViewModel as
// Kotlin var property
class PersonVarViewModel(person: Person) : ViewModel() {
val name = bind { person.observable(Person::name) }
}
It seems like doesn't work.
How to solve this issue. IDE shows red underline bellow "bind"
but if i write
val name = bind(RoomType::name)
it shows no error. but updating the value using UI fields does'nt update the model value.
Please help
In your class declaration, use var person: Person.
person needs to be a member of the class, not just a parameter to the constructor. You can do this by declaring it var or val in the constructor parameters, or you can add a member field to the class the conventional way and assign it (probably using by property, but not sure if that's what you want)
class PersonVarViewModel(var person: Person) : ViewModel() {
val name = bind { person.observable(Person::name) }
}
For ItemViewModel ...
class PersonVarViewModel(var person: Person) : ItemViewModel<Person>() {
val name = bind { person.observable(Person::name) }
}
You need to make the ItemViewModel aware of the person instance, but also let it react to changes to the underlying item later. You need to assign the person you pass in to the item property of the ItemViewModel. This can be done by passing it in the constructor:
class PersonVarViewModel(person: Person) : ItemViewModel<Person>(person) {
val name = bind(Person::name)
}
Be aware that if you add this constructor, you can only use the that viewmodel with injection if you push it manually into scopes, since it can't be instantiated by the framework. You should therefore either add a noargs constructor as well, or simply omit the person parameter and assign to item after you create it.
If you update the value in the underlying person, it will only be visible in the view model if the value is observable. If not, you have to call rollback() to update changes from the person. You can call rollback for specific fields only.
If possible, use observable properties in your domain model objects to avoid such issues.