hello everyone in ktor when some expected fields i...

# ktor

[Reham Galal]

hello everyone
in ktor when some expected fields isn't received in the response I got an
io.ktor.serialization.JsonConvertException: Illegal input: Fields [name] are required for type with serial name 'UserDTO', but they were missing at path: $.User.name

[Aleksei Tirman [JB]]

Can you describe the problem?

[Reham Galal]

I expect the not received fields to be ignored if not received

[Moussa]

This error occurs because your DTO class expects certain fields that aren't present in the JSON response. You can go about it with one of these:

• Make Fields Nullable

@Serializable
data class DTO(val name: String? = null)

• Add Default Values

@Serializable
data class DTO(val name: String = "default-name")

• isLenient to true
In your Json configuration from kotlinx.serlization inside ktor you can set isLenient to true

[Reham Galal]

but this is different from retrofit in retrofit it will ignore it by default

[Moussa]

Retrofit is using Gson for serlization while ktor is using kotlinx.serlization
Different libs, different behaviour
There is also ignoreUnknownKeys to ignore any keys that are extra or you don't want to add to your model

install(ContentNegotiation) {
        json(Json {
            isLenient = true            
            ignoreUnknownKeys = true // Ignore unknown keys in JSON (optional)
        })
    }

example

{
  "username": "moussa147",
  "pass": "123456",
  "hello": "world"
}

@Serializable
data class Model(val username: String, val pass: String)

When you use ignoreUnknownKeys it will ignore the hello in the JSON

[Reham Galal]

got you thank you @Moussa 🙏