Spring Boot request body semi-required fields - spring

Question

In our application user can write a message based on user id or screen name.
class Message {
public final Long userId;
public final String screenName;
public final String text;
#JsonCreator
public Message(#JsonProperty(value = "user_id", required = ???) Long userId,
#JsonProperty(value = "screen_name", required = ???) String screenName,
#JsonProperty(value = "text", required = true) String text) {
this.userId = userId;
this.screenName = screenName;
this.text = text;
}
}
Fields userId and screenName can't be optional at same time, one should be provided.
How in Spring Boot to mark that they are semi-required?

Answer 1

This seems like more of a validation concern rather than deserialization.
Create a Validator then put #Valid within the #RequestMapping on the controller.
See more here:
Spring REST Validation Example

Answer 2

From jenkov tutorials:
#JsonValue
The Jackson annotation #JsonValue tells Jackson that Jackson should
not attempt to serialize the object itself, but rather call a method
on the object which serializes the object to a JSON string. Note that
Jackson will escape any quotation marks inside the String returned by
the custom serialization, so you cannot return e.g. a full JSON
object. For that you should use #JsonRawValue instead (see previous
section).
The #JsonValue annotation is added to the method that Jackson is to
call to serialize the object into a JSON string. Here is an example
showing how to use the #JsonValue annotation:
public class PersonValue {
public long personId = 0;
public String name = null;
#JsonValue
public String toJson(){
return this.personId + "," + this.name;
}
}
The output you would get from asking Jackson to serialize a
PersonValue object is this:
"0,null"
So you can use #JsonValue and put your code either to ignore or not from some fields when you try to convert into JSON
#JsonValue
public String toJson(){
//ignore fields or include them here
}

Answer 3

Just throw an IllegalArgumentException. The best case would be to deserialize, then run through a validator though so you separate the concerns of serialization, and domain validation.
class Message {
public final Long userId;
public final String screenName;
public final String text;
#JsonCreator
public Message(#JsonProperty(value = "user_id", required = false) Long userId,
#JsonProperty(value = "screen_name", required = false) String screenName,
#JsonProperty(value = "text", required = true) String text) {
if(userId == null && screenName == null) {
throw new IllegalArgumentException("userId or screenName must be provided.");
}
this.userId = userId;
this.screenName = screenName;
this.text = text;
}
}