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kotlinlang

Hi guys, what is the best practice for Spring Data JPA Entity written in Kotlin, using `data class` or `class` with `lateinit var`, those field in entity mostly don’t have default value

I would read <https://spring.io/guides/tutorials/spring-boot-kotlin/>

summary, regular class and `var` are better off than data classes, you can also have

```
class Entity(
  var id: String, 
  ..., 
  var middleName: String? = null)
```

and I suggest to have preinitialized values at the bottom of the constructor list, so you can do `Entity(mandatoryOne, mandatoryTwo)`. if you have optional values in the middle of the parameter list, you would have to pass them as well

I would avoid data classes for Entities.
This is a good starting point with some nice in-depth explanations:
<https://kotlinexpertise.com/hibernate-with-kotlin-spring-boot/>

for JPA, i usually use kotlin no-arg plugin + data class, so it will generate the no-argument default constructor for you without the burden to specify default values or make them lateinit var, and still give you all the benefit of data class.
@MyNoArgConstructorAnnotation
data class MyEntity(
  var id: Long,
  var name: String
)

<@U3ZLPSCAC> that blog post specifically says don't do that?  "Do not use data classes to define your @Entity classes - JPA doesn't work well with the generated equals/hashCode functions."

<@UKM355HBM> ah, i guess you’re right. i should not use data class but only the no-arg plugin to avoid specifying default values or using lateinit var. so the class should look like this:
```@MyNoArgConstructorAnnotation
class MyEntity(
 var id: Long,
 var name: String
) : BaseEntity(id)
```

and btw, myself prefer using mybatis and spring jdbc