Json4s not serializing Java classes-CodePudding

I have some scala code that needs to be able to serialize/deserialize some Java classes using Json4s.

I am using "org.json4s" %% "json4s-ext" % "4.0.5" and "org.json4s" %% "json4s-jackson" % "4.0.5" though I have also tried with the 3.6.7 version.

Model Code (Java):

import com.fasterxml.jackson.annotation.JsonProperty;

public class Blah {
    @JsonProperty("what")
    public final String what;

    public Blah() {
        this(null);
    }
    public Blah(String what) {
        this.what = what;
    }
}

Serialization (Scala):

import org.json4s.DefaultFormats
import org.json4s.jackson.Serialization

println(Serialization.write(new Blah("helloooo!!!!"))(DefaultFormats))

It only ever prints out: {}.

I understand I can write a CustomSerializer for each Java class but I have a lot of Java classes and would really like to avoid doing that. Any ideas on how to make this work?

CodePudding user response：

Try to add getter method for your what property

CodePudding user response：

Json4s ignores any JsonProperty annotation and requires both a constructor parameter and a Scala case-class style getter method for each property of your Java model class. In the example above that would look like:

public class Blah {
    private final String what;

    public String what() {
        return what;
    }

    public Blah() {
        this(null);
    }
    public Blah(String what) {
        this.what = what;
    }
}