👀 Views: 27 💬 Answers: 1 📅 Created: 2025-06-08

java jackson serialization Java

I'm facing an issue with custom serialization of nested objects using Jackson in my Java 11 application. I have a parent object `User` that contains a nested object `Profile`. I implemented a custom serializer for the `Profile` class, but when I serialize a `User` object, the `Profile` fields are returning null, even though they are populated. I've defined a `@JsonSerialize` annotation on the `Profile` field in the `User` class, but it seems like the custom serializer is not being invoked as expected. Here’s the relevant part of the code: ```java import com.fasterxml.jackson.core.JsonGenerator; import com.fasterxml.jackson.databind.JsonSerializer; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.annotation.JsonSerialize; import java.io.IOException; class User { private String name; @JsonSerialize(using = ProfileSerializer.class) private Profile profile; // Constructor, getters and setters } class Profile { private String bio; private String avatarUrl; // Constructor, getters and setters } class ProfileSerializer extends JsonSerializer<Profile> { @Override public void serialize(Profile profile, JsonGenerator gen, com.fasterxml.jackson.databind.SerializerProvider serializers) throws IOException { gen.writeStartObject(); gen.writeStringField("bio", profile.getBio()); gen.writeStringField("avatarUrl", profile.getAvatarUrl()); gen.writeEndObject(); } } ``` When I serialize a `User` object like this: ```java User user = new User("John Doe", new Profile("Hello World!", "http://example.com/avatar.jpg")); ObjectMapper mapper = new ObjectMapper(); String result = mapper.writeValueAsString(user); System.out.println(result); ``` It outputs: ```json {"name":"John Doe","profile":null} ``` I’ve already checked that the `Profile` object is correctly initialized and not null before serialization. Also, I made sure that the custom serializer is properly referenced. What could be causing the `profile` field to be serialized as null? Is there something I might be missing in the configuration or in the way I’m setting up serialization? Any ideas what could be causing this? My team is using Java for this CLI tool. Is there a better approach?