Json4s (Native/Jackson) Ignore all unknown fields

Question

When using Json4s it was very clear you can explicitly ignore specific fields. However, I don't see any documentation on how to ignore all unknown fields.

In Jackson, I would use the following annotation:

import com.fasterxml.jackson.annotation._

@JsonIgnoreProperties(ignoreUnknown=true)
case class MyClass(string: String)

How do I do this with either the Jackson or Native version of Json4s?

Answer 1

I'm not quite sure, if I get you here, but Json4s (at least the org.json4s version) ignores additional fields by default.

import org.json4s.DefaultFormats
import org.json4s.native.JsonMethods._

implicit val formats = DefaultFormats
case class Mailserver(url: String, username: String, password: String)

val json = parse(
"""
  {
    "url": "imap.yahoo.com",
    "username": "myusername",
    "password": "mypassword",
    "additional": "field"
  }
"""
)

val m = json.extract[Mailserver]
println(m.url)
println(m.username)
println(m.password)

This works fine.