How to Create a Custom Jackson Date Serializer in Spring Boot

Apr 23, 2026

Purpose

This post shows how to create a custom Jackson date serializer in Spring Boot when you cannot use @JsonFormat annotations on auto-generated classes.

Environment

Spring Boot 2.x / 3.x
Jackson 2.x
Java 8+

The Problem

I needed to serialize java.util.Date fields in a custom format, but the DTO classes were auto-generated by an older system. Adding @JsonFormat annotations was not an option.

The property-based configuration spring.jackson.date-format has limitations:

Only supports a single global format
Doesn’t work when custom beans override auto-configuration
Cannot handle different formats for different fields

The Solution

Create a custom JsonSerializer<Date> and register it globally via Jackson2ObjectMapperBuilderCustomizer. This gives complete control over date serialization without modifying DTO classes.

Step 1: Create the Custom Serializer

package com.example.config;

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

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class CustomDateSerializer extends JsonSerializer<Date> {

    private static final SimpleDateFormat dateFormat =
        new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");

    @Override
    public void serialize(Date value, JsonGenerator gen,
                          SerializerProvider serializers) throws IOException {
        String formattedDate = dateFormat.format(value);
        gen.writeString(formattedDate);
    }
}

Important: Import java.util.Date, not java.sql.Date. The serializer must match the field type in your POJOs.

Step 2: Register the Serializer Globally

Use Jackson2ObjectMapperBuilderCustomizer for a clean configuration:

package com.example.config;

import com.fasterxml.jackson.databind.SerializationFeature;
import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.Date;

@Configuration
public class JacksonConfig {

    @Bean
    public Jackson2ObjectMapperBuilderCustomizer jsonCustomizer() {
        return builder -> {
            builder.serializers(new CustomDateSerializer());
            builder.featuresToDisable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
        };
    }
}

This approach:

Registers the serializer for all Date fields globally
Disables timestamp serialization as baseline
Works with Spring Boot’s auto-configuration

Step 3: Alternative with SimpleModule

For more control, use SimpleModule directly:

package com.example.config;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilderCustomizer;

import java.util.Date;

@Configuration
public class JacksonModuleConfig {

    @Bean
    public Jackson2ObjectMapperBuilderCustomizer jsonCustomizer() {
        return builder -> {
            SimpleModule module = new SimpleModule();
            module.addSerializer(Date.class, new CustomDateSerializer());
            builder.modules(module);
            builder.featuresToDisable(
                SerializationFeature.WRITE_DATES_AS_TIMESTAMPS
            );
        };
    }
}

How It Works

Serializer Registration: The custom serializer intercepts all Date serialization calls
Format Control: The SimpleDateFormat inside the serializer defines the output format
Global Application: Once registered, all Date fields use this format without code changes

Testing the Configuration

package com.example;

import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.Date;

import static org.assertj.core.api.Assertions.assertThat;

@SpringBootTest
class DateSerializationTest {

    @Autowired
    private ObjectMapper objectMapper;

    @Test
    void shouldSerializeDateWithCustomFormat() throws Exception {
        Date date = new Date(1704067200000L); // 2024-01-01 00:00:00 UTC

        String json = objectMapper.writeValueAsString(date);

        assertThat(json).contains("2024");
        assertThat(json).doesNotContain(":"); // No timestamp format
    }
}

Common Mistakes to Avoid

Wrong import: Using java.sql.Date instead of java.util.Date
Missing module registration: Not calling builder.modules(module)
Timestamp baseline: Forgetting to disable WRITE_DATES_AS_TIMESTAMPS
Thread safety: SimpleDateFormat is not thread-safe - create new instances or use ThreadLocal

Summary

In this post, I showed how to create a custom Jackson date serializer in Spring Boot when @JsonFormat annotations are not available. The solution uses JsonSerializer<Date> with Jackson2ObjectMapperBuilderCustomizer for global registration. This approach works well with auto-generated DTOs and provides full control over date formatting.

Final Words + More Resources

My intention with this article was to help others share my knowledge and experience. If you want to contact me, you can contact by email: Email me

Here are also the most important links from this article along with some further resources that will help you in this scope:

👨‍💻 Stack Overflow: Custom Jackson Date Serializer in Spring Boot

Oh, and if you found these resources useful, don’t forget to support me by starring the repo on GitHub!