Kotlin, . , Kotlin , .
: Kotlin . .
1. Annotation Processors
, Kotlin Java, Java , , JPA , , QueryDsl. annotation processor ( ).
:
- , annotation processor .
- annotation processor Java ( Kotlin). maven, : Kotlin, annotation processor, Java.
- kapt ( QueryDsl )
2.
. , :
class UserWithField(param: String) {
@NotEmpty var field: String = param
}
:
class UserWithConstructor(
@NotEmpty var paramAndField: String
)
(ElementType.PARAMETER), . :
class UserWithFixedConstructor(
@field:NotEmpty var paramAndField: String
)
JetBrains,
. . .
: @field: , (
javax.persistence.Column), .
3. setter
. , , ( ?). :
class NotDefaultSetterTest {
@Test fun customSetter() {
val ivan = User("Ivan")
assertEquals("Ivan", ivan.name)
ivan.name = "Ivan"
assertEquals("IVAN", ivan.name)
}
class User(
nameParam: String
) {
var name: String = nameParam
set(value) {
field = value.toUpperCase()
}
}
}
, setter, , , , setter. ( -, , ):
class User(
nameParam: String
) {
var name: String = nameParam.toUpperCase()
set(value) {
field = value.toUpperCase()
}
}
4.
Spring Hibernate, , . not final .
JSF. , Java-, getter-setter. , , , . , JSF , setter . , JSF, mutable. DTO.
JSF . , , , . view.
: . , / .
, .
5. ,
. get-set, null-safe, , extensions .
:
fun getBalance(group: ClassGroup, month: Date, payments: Map>): Balance {
val errors = mutableListOf()
fun tryGetBalanceItem(block: () -> Balance.Item) = try {
block()
} catch(e: LackOfInformation) {
errors += e.message!!
Balance.Item.empty
}
val credit = tryGetBalanceItem {
creditBalancePart(group, month, payments)
}
val salary = tryGetBalanceItem {
salaryBalancePart(group, month)
}
val rent = tryGetBalanceItem {
rentBalancePart(group, month)
}
return Balance(credit, salary, rent, errors)
}
. , ( , ).
, try, if when , ( ). try/catch, , Java- :
val result: String
try {
//some code
result = "first"
//some other code
} catch (e: Exception) {
result = "second"
}
, result , immutable.
: fun tryGetBalanceItem . JavaScript, .
, tryGetBalanceItem try. , .
6.
. , .
, , User , . , , DTO.
data class User (
val name: String,
val birthDate: Date,
val created: Date = Date()
)
fun usageVersion1() {
val newUser = User("Ivan", SEPTEMBER_1990)
val userFromDto = User(userDto.name, userDto.birthDate, userDto.created)
}
disabled, , created, User :
data class User (
val name: String,
val birthDate: Date,
val created: Date = Date(),
val disabled: Boolean = false
)
fun usageVersion2() {
val newUser = User("Ivan", SEPTEMBER_1990)
val userFromDto = User(userDto.name, userDto.birthDate, userDto.created, userDto.disabled)
}
: usageVersion1 . . , , . , ,
7. ,
val months: List = ...
val hallsRents: Map> = months
.map { month ->
month to halls
.map { it.name to rent(month, it) }
.toMap()
}
.toMap()
Map Map. , . it, - , . , .
, , . : hallsRents MutableMap, .
. :
val months: List = ...
val hallsRents: Map> = months
.map { it to rentsByHallNames(it) }
.toMap()
, . - , , .
: 8500 , Kotlin ( ). , , . prod , : NPE ( ) ehcache ( ).
PS. , Kotlin.
https://habrahabr.ru/post/331280/
