I made controller method.
I want the method to receive variable defined by own original Data type.
like Below,
data class UserId(
val value: UUID
)
#GetMapping("user/{userId}")
fun getUser(
#PathVariable userId: UserId
) {
userService.getUser(userId)
}
Of course, I know how to receive variable of String.
#GetMapping("user/{userId}")
fun getUser(
#PathVariable userId: String
) {
// I think this code is redundancy.
val id = UserId.fromString(userId)
userService.getUser(userId)
}
Can I receive variable defined own original Data Type?
Do you know any idea?
The main question is, how do you see this working? Would you receive the data class as a serializable JSON object? If so, shouldn't that be inputted as the request body?
If there's another way you envision this working, you can always manually serialize the object later, something like:
Controller:
#GetMapping("user/{userId}")
fun getUser(
#PathVariable userIdSerialized: String
) {
userService.getUser(userIdSerialized)
}
Service:
fun getUser(userIdSerialized: String) {
// Using Jackson
val deserialized: UserId = mapper.readValueFromString(userIdSerialized, UserId::class.java)
}
But again, this should really be a request body.
Related
I have a controller:
#PostMapping
fun create(
#RequestBody #Valid request: MyContainer<CreateRequest>,
): MyContainer<Dto> = service.create(request.objects)
with MyContainer and CreateRequest looking something like this:
class MyContainer<T>(
#field:Valid // also tried param
#field:NotEmpty(message = "The list of objects can not be null or empty")
var objects: List<#Valid T>? = listOf(),
)
class CreateRequest(
#field:NotNull(message = "Value can not be null")
var value: BigDecimal? = null,
)
In my tests, the "outer" validation works, that is I do get the expected error message if I send it { "objects": null } or { "objects": [] }. But I can not get it to validate the contents of the list. From what I understand in Java List<#Valid T> should work, but for whatever I can not get it to work in kotlin.
I figured I might need some kind of use-site target on #Valid in List<#Valid T>, but I can't find one that's applicable for this use case.
How can I get the validation to work for the list?
I managed to find a solution myself.
Apparently get: is the correct use-site target, not field: or param:. Furthermore the #Valid in List<#Valid T> was not necessary.
For reference, here's the working class (also changed it back to a data class as that doesn't seem to pose an issue).
class MyContainer<T>(
#get:Valid
#get:NotEmpty(message = "The list of objects can not be null or empty")
var objects: List<T>? = listOf(),
)
and the CreateRequest:
class CreateRequest(
#get:NotNull(message = "Value can not be null")
var value: BigDecimal? = null,
)
Changing to the get: use-site target was only necessary for #Valid, but I opted for using it everywhere for consistency and since it seems to be the one that works best.
I have an endpoint which can accept dozens of request params. It would be nice to collect all these params in a data class. Additionally, the request params must be separated by commas
path?param=1,2
to keep backward compatibility.
Assume we have this endpoint:
#GetMapping("path")
fun someFun(#RequestParam param: Set<Int> = emptySet()
...other 11 params
)
I created a data class to collect all the request params:
data class ClusteredParams(val param: Set<Int> = emptySet()
...other 11 params
)
So the endpoint looks like the following:
#GetMapping("path")
fun someFun(param: ClusteredParams)
When I called path?param=1,2 I got:
"error": "Failed to convert value of type java.lang.String[] to required type java.util.Set; nested exception is java.lang.NumberFormatException: For input string: "1,2"",
"field": "param",
"rejectedValue": "1,2"
When I call path?param=1¶m=2 everything is fine. This problem does not exist when ClusteredParams class is written in Java.
public class ClusteredParams {
private Set<Int> param;
...other 11 params
getters and setters
}
I don't know the answer, but I did the comparison what works and when:
in Java:
You can either call ?path=1,2 and ?path=1&path=2 no matter if your request param is declared using #RequestParam path: List<Int> inside signature of controller method, or it is a field of external object that's used to group all request params of controller method.
In Kotlin:
if you declare your request param inside of controller method signature, as a #RequestParam path: List<Int> or whatever else, you can call it using both methods, so:
?path=1,2 and ?path=1&path=2
If you however extract it to separate data class, and then expect this class to be populated in controller method, you can only do the ?path=1&path=2, because in the case of ?path=1,2 you get:
org.springframework.validation.BindException because it tries to parse entire '1,2' instead of split it first.
I hope now it is more clear, does anyone have idea why this happens?
Instead of val use var inside data class body:
data class ClusteredParams(
...other 11 params
) {
var param: Set<Int> = emptySet()
}
The problem's pretty straightforward. I have a couple of events that derive from the same interface, and I'd like to deserialize them to their propper super-class.
I know how to do that with an object mapper, but using my own mapper would mean letting Spring-Boot parse the #RequestBody as a String and then doing it myself, which isn't the worlds end, but I can't help but suspect that Spring provides proper tools to handle this kind of situation. Trouble is, I can't seem to find them.
Here's a bit of sample code:
example event:
interface YellowOpsEvent {
val user: String
val partner: String
val subject: String
val change: NatureOfChange
}
data class StatusChangedEvent(override val user: String,
override val partner: String,
override val subject: String,
val before: String,
val after: String): YellowOpsEvent {
override val change = NatureOfChange.Changed
}
controller:
#PostMapping("/event")
fun writeEvent(#RequestBody event: YellowOpsEvent) { // < I expect this not to throw an exception
val bugme = event is StatusChangedEvent // < I expect this to return true if I send the proper event data.
}
Just to clarify, I perfectly understand why this doesn't work out of the box. The trouble is, I can't find out what I need to do to make it work.
The link in pL4Gu33's comment lead me in the right direction, but it took some additional searching and fiddling, plucking information from here and there to arrive at the solution that would finally work, so I'm summarising it here for completeness.
The trouble is that you'll need two annotations, one on the interface and one on the implementing classes, the combined use of which seems somewhat ill-documented.
First, on the interface, add this annotation. Contrary to some tutorials you will find, no further annotation of the interface is required:
#JsonTypeInfo(use=JsonTypeInfo.Id.CLASS, include=JsonTypeInfo.As.PROPERTY, property="#class")
interface YellowOpsEvent {
val user: String
val partner: String
val subject: String
val change: NatureOfChange
}
According to some documentation, this alone should be enough for propper deserialisation. The spring-boot controller, however, will throw an exception because the passed root name does not match the class it was expecting.
// the above will throw an exception when the serialization product is sent to this controller:
#PostMapping("/event")
fun writeEvent(#RequestBody event: YellowOpsEvent) { // < I expect this not to throw an exception
val bugme = event is StatusChangedEvent // < I expect this to return true if I send the proper event data.
}
To fix that, add the #JsonRootName annotation to any implementing classes, with the interface's name. Most documentation of this annotation don't use it for this, instead just for renaming the type, and even when it's mentioned in the linked question in the context of polymorphism, it wrongly uses its own name. This is what it needs to look like:
#JsonRootName("YellowOpsEvent")
data class StatusChangedEvent(override val user: String,
override val partner: String,
override val subject: String,
val before: String,
val after: String): YellowOpsEvent {
override val change = NatureOfChange.Changed
}
Now it works! :)
I have backend that return me some json.
I parse it to my class:
class SomeData(
#SerializedName("user_name") val name: String,
#SerializedName("user_city") val city: String,
var notNullableValue: String
)
Use gson converter factory:
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(ENDPOINT)
.client(okHttpClient)
.addConverterFactory(GsonConverterFactory.create(gson))
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
.build();
And in my interface:
interface MyAPI {
#GET("get_data")
Observable<List<SomeData>> getSomeData();
}
Then I retrieve data from the server (with rxJava) without any error. But I expected an error because I thought I should do something like this (to prevent GSON converter error, because notNullableValue is not present in my JSON response):
class SomeData #JvmOverloads constructor(
#SerializedName("user_name") val name: String,
#SerializedName("user_city") val city: String,
var notNullableValue: String = ""
)
After the data is received from backend and parsed to my SomeData class with constructor without def value, the value of the notNullableValue == null.
As I understand not nullable value can be null in Kotlin?
Yes, that is because you're giving it a default value. Ofcourse it will never be null. That's the whole point of a default value.
Remove ="" from constructor and you will get an error.
Edit: Found the issue. GSON uses the magic sun.misc.Unsafe class which has an allocateInstance method which is obviously considered very unsafe because what it does is skip initialization (constructors/field initializers and the like) and security checks. So there is your answer why a Kotlin non-nullable field can be null. Offending code is in com/google/gson/internal/ConstructorConstructor.java:223
Some interesting details about the Unsafe class: http://mishadoff.com/blog/java-magic-part-4-sun-dot-misc-dot-unsafe/
Try to override constructor like this:
class SomeData(
#SerializedName("user_name") val name: String,
#SerializedName("user_city") val city: String,
var notNullableValue: String = "") {
constructor() : this("","","")
}
Now after server response you can check the notNullableValue is not null - its empty
In data class I defined the 'name' must be unique across whole mongo collection:
#Document
data class Inn(#Indexed(unique = true) val name: String,
val description: String) {
#Id
var id: String = UUID.randomUUID().toString()
var intro: String = ""
}
So in service I have to capture the unexpected exception if someone pass the same name again.
#Service
class InnService(val repository: InnRepository) {
fun create(inn: Mono<Inn>): Mono<Inn> =
repository
.create(inn)
.onErrorMap(
DuplicateKeyException::class.java,
{ err -> InnAlreadyExistedException("The inn already existed", err) }
)
}
This is OK, but what if I want to add more info to the exceptional message like "The inn named '$it.name' already existed", what should I do for transforming exception with enriched message.
Clearly, assign Mono<Inn> to a local variable at the beginning is not a good idea...
Similar situation in handler, I'd like to give client more info which derived from the customized exception, but no proper way can be found.
#Component
class InnHandler(val innService: InnService) {
fun create(req: ServerRequest): Mono<ServerResponse> {
return innService
.create(req.bodyToMono<Inn>())
.flatMap {
created(URI.create("/api/inns/${it.id}"))
.contentType(MediaType.APPLICATION_JSON_UTF8).body(it.toMono())
}
.onErrorReturn(
InnAlreadyExistedException::class.java,
badRequest().body(mapOf("code" to "SF400", "message" to t.message).toMono()).block()
)
}
}
In reactor, you aren't going to have the value you want handed to you in onErrorMap as an argument, you just get the Throwable. However, in Kotlin you can reach outside the scope of the error handler and just refer to inn directly. You don't need to change much:
fun create(inn: Mono<Inn>): Mono<Inn> =
repository
.create(inn)
.onErrorMap(
DuplicateKeyException::class.java,
{ InnAlreadyExistedException("The inn ${inn.name} already existed", it) }
)
}