英文:
Compile error while returning chunked response from play 2.8.18
问题
我正在尝试在Play框架中使用分块响应。
以下控制器代码正常运行。
def chunkedSample = Action {
val source = Source.apply(List("Hello","Hai"))
Ok.chunked(source)
}
但当我将List对象更改为如下的案例类时
def chunkedSample = Action {
val source = Source.apply(List(Dummy("hello")))
Ok.chunked(source)
}
我得到以下编译错误
`找不到参数writable的隐式值:Writable[Dummy]`
我尝试将json格式和写入放在下面的伴随对象中，但没有起作用。
object Dummy{
implicit val write = Json.writes[Dummy]
}
英文:
I am trying out chunked response in play framework.
The below controller code works fine.
def chunkedSample = Action {
val source = Source.apply(List("Hello","Hai"))
Ok.chunked(source)
}
But when I change the List object to a case class as below
def chunkedSample = Action {
val source = Source.apply(List(Dummy("hello")))
Ok.chunked(source)
}
Where I define dummy case class as below
case class Dummy(hello:String)
I get below compilation error
No implicit found for parameter writable:Writable[Dummy]
I tried putting json format & writes in companion object below but didn't work.
object Dummy{
implicit val write = Json.writes[Dummy]
}
答案1
得分: 1
The error tells you that you are missing writes, so you need to add them. There are different ways to add them, but for case class I find next example as most convenient. It also has read as you will most probably need it in the future.
case class Dummy(hello: String)
implicit lazy val dummyReads: Reads[Dummy] = (
(__ \ "hello").read[String]
)(Dummy)
implicit lazy val dummyWrites: Writes[Dummy] = (
(__ \ "hello").write[String]
)(unlift(Dummy.unapply))
More documentation could be found on this page of Play framework official docs.
英文:
The error tells you that you are missing writes, so you need to add them. There are different ways to add them, but for case class I find next example as most convenient. It also has read as you will most probably need it in the future.
case class Dummy(hello: String)
implicit lazy val dummyReads: Reads[Dummy] = (
(__ \ "hello").read[String]
)(Dummy)
implicit lazy val dummyWrites: Writes[Dummy] = (
(__ \ "hello").write[String]
)(unlift(Dummy.unapply))
More documentation could be found on this page of Play framework official docs.
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