I’m developing JAX-RS based application and Payara server. I want to serialize build in java Color class to String format: color = "RcolorValu, GColorValue, BColor value”. For example in form "255,255,255". That’s why I’ve written custom serializer:

package org.example;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

import java.awt.*;
import java.io.IOException;
import java.util.logging.Logger;
public class ColorSerializer extends JsonSerializer<Color> {
    private static final Logger logger = Logger.getLogger(ColorSerializer.class.getName());

    @Override
    public void serialize(Color color, JsonGenerator generator, SerializerProvider serializers) throws IOException {
        logger.info("Serializing color init ");
        if (color == null) {
            generator.writeNull();
        } else {
            String colorString = color.getRed() + "," + color.getGreen() + "," + color.getBlue();
            logger.info("Serializing color: " + colorString); // Add logging
            generator.writeString(colorString);
        }
    }
}

I also’ve registered it in ObjectMapperProvider like below:

package org.example;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import jakarta.enterprise.context.ApplicationScoped;
import jakarta.ws.rs.Produces;
import jakarta.ws.rs.ext.ContextResolver;
import jakarta.ws.rs.ext.Provider;

import java.awt.*;

@Provider
public class ObjectMapperProvider implements ContextResolver<ObjectMapper> {

    private final ObjectMapper objectMapper;

    public ObjectMapperProvider() {
        // Register the JavaTimeModule for date/time serialization
        objectMapper = new ObjectMapper();
        objectMapper.registerModule(new JavaTimeModule());
        objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);

        // Register the custom ColorSerializer
        SimpleModule module = new SimpleModule();
        module.addSerializer(Color.class, new ColorSerializer());
        objectMapper.registerModule(module);
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    }

    @Override
    public ObjectMapper getContext(Class<?> type) {
        return objectMapper;
    }
}

My Employee entity class with favoriteColor property and annotation @JsonSerialize(using = ColorSerializer.class) which should cause serialization is in form like below:

package org.example;

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import jakarta.json.bind.annotation.JsonbDateFormat;
import jakarta.persistence.*;

import java.awt.*;
import java.io.Serializable;
import java.util.Date;

@Entity
@Table(name = "Employee")
public class Employee implements Serializable {

    @Id
    @Column(name = "EMPLOYEE_ID")
    private Long id;

    @Column(name = "FIRST_NAME")
    private String firstName;

    @Column(name = "LAST_NAME")
    private String lastName;


    public Date getHireDate() {
        return hireDate;
    }

    public void setHireDate(Date hireDate) {
        this.hireDate = hireDate;
    }

    @Column(name = "HIRE_DATE")
    @Temporal(TemporalType.DATE)
    @JsonbDateFormat("yyyy-MM-dd")
    private Date hireDate;

    @Column(name = "GENDER")
    @Enumerated(EnumType.STRING)
    private Gender gender;

    public Color getFavoriteColor() {
        return favoriteColor;
    }

    public void setFavoriteColor(Color favoriteColor) {
        this.favoriteColor = favoriteColor;
    }

    @Column(name = "FAVORITE_COLOR")
    @Convert(converter = ColorConverter.class)
    @JsonSerialize(using = ColorSerializer.class)
    private Color favoriteColor;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public Gender getGender() {
        return gender;
    }

    public void setGender(Gender gender) {
        this.gender = gender;
    }
}

And my EmployeeResource with list of employee endpoint which should return list of Employees:

package org.example;

import jakarta.enterprise.context.RequestScoped;
import jakarta.inject.Inject;
import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;
import jakarta.ws.rs.Produces;
import jakarta.ws.rs.core.MediaType;

import java.util.List;
import java.util.logging.Logger;

@Path("/employee")
@RequestScoped
public class EmployeeResource {

    @Inject
    private EmployeeService employeeService;

    private static final Logger logger = Logger.getLogger(EmployeeService.class.getName());


    @GET
    @Produces(MediaType.APPLICATION_JSON)
    @Path("/")
    public List<Employee> getEmployees() {
        logger.info("Retrieving all employees");
        return employeeService.getAllEmployees();
    }   
}

Besides that I configured Converter which works. I figured out it from logs but Serializer dosen’t :

package org.example;

import jakarta.persistence.AttributeConverter;
import jakarta.persistence.Converter;

import java.awt.*;
import java.util.logging.Logger;

@Converter(autoApply = true)
public class ColorConverter implements AttributeConverter<Color, String> {

    private static final Logger logger = Logger.getLogger(ColorSerializer.class.getName());


    @Override
    public String convertToDatabaseColumn(Color attribute) {
        logger.info("converter color color: " + attribute.toString()); // Add logging
        return attribute.getRed() +
                "," +
                attribute.getGreen() +
                "," +
                attribute.getBlue();
    }

    @Override
    public Color convertToEntityAttribute(String dbData) {
        if (dbData == null || dbData.isBlank()) {
            return null;
        }
        String[] parts = dbData.split(",");
        Color color = new Color(Integer.parseInt(parts[0]), Integer.parseInt(parts[1]), Integer.parseInt(parts[2]));
        logger.info("Converting DB data to color: " + color.toString()); // Add logging
        return color;
    }
}

In any case I receive every time json response like:

Example data in database:

I don’t know how to leverage using my Custom Serializer instead of build in.