👀 Views: 0 💬 Answers: 1 📅 Created: 2025-06-16

java spring-boot jackson Java

I'm prototyping a solution and I'm converting an old project and After trying multiple solutions online, I still can't figure this out. I am currently working on a Spring Boot 2.6 application where I need to serialize a custom date object into a specific format using Jackson's ObjectMapper. I have defined a custom serializer for my date object, but it seems that the serialization only works intermittently. In some cases, the date is serialized to the desired format, while in others, it defaults to the standard ISO format. Here’s my custom serializer: ```java 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 formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); @Override public void serialize(Date date, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException { if (date != null) { jsonGenerator.writeString(formatter.format(date)); } } } ``` I registered this serializer in my `@JsonComponent` like this: ```java 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.Jackson2ObjectMapperBuilder; @Configuration public class JacksonConfig { @Bean public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder) { SimpleModule module = new SimpleModule(); module.addSerializer(Date.class, new CustomDateSerializer()); builder.modules(module); return builder.build(); } } ``` However, when I try to serialize a list of objects containing date fields, I sometimes get the following behavior: `com.fasterxml.jackson.databind.exc.InvalidDefinitionException: want to construct instance of 'java.util.Date' (no Creators, like default constructor, exist): not marked as ignorable`. I’ve ensured that my date field is correctly annotated, but I still face issues when the date is not correctly formatted. I tried adjusting the module registration order, but it didn’t help. I also double-checked that all date fields are initialized before serialization. What am I missing? Is there a specific configuration or best practice I should follow to ensure consistent serialization with Jackson in this scenario? I'm coming from a different tech stack and learning Java. What's the best practice here? The stack includes Java and several other technologies. I appreciate any insights! My development environment is Linux. I appreciate any insights!