How to Properly Format Java 8 LocalDate Objects in JSON using Jackson?

Formatting Java 8 LocalDate with Jackson

Problem:

In Java applications, converting Date objects into JSON format with specific date patterns can be straightforward using the @JsonFormat annotation. However, when dealing with java.time.LocalDate introduced in Java 8, the same approach may not work as expected.

Proposed Solution:

To customize the formatting of LocalDate objects for JSON serialization, the following approach can be used:

1. Configure Jackson ObjectMapper:
2. Create a ContextResolver implementation for ObjectMapper.
3. Register the JavaTimeModule in the ObjectMapper to support LocalDate serialization.
4. Enable the WRITE_DATES_AS_TIMESTAMPS feature to false, as LocalDate represents dates without timestamps.
5. Use ContextResolver in JAX-RS Application:
6. Define a JAX-RS service class with @Provider annotation.
7. Implement the ObjectMapperContextResolver interface to provide the configured ObjectMapper.
8. Annotate Resource Class for JSON Conversion:
9. Add the @JsonDeserialize and @JsonSerialize annotations with proper deserializer and serializer classes to handle LocalDate conversion.

Example Code:

ContextResolver:

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;

@Provider
public class ObjectMapperContextResolver implements ContextResolver<ObjectMapper> {
    @Override
    public ObjectMapper getContext(Class<?> type) {
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerModule(new JavaTimeModule());
        mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
        return mapper;
    }
}

Resource Class:

import java.time.LocalDate;

@Path("person")
public class LocalDateResource {
    @GET
    public Person getPerson() {
        return new Person(LocalDate.now());
    }
}

Person Class:

public class Person {
    @JsonDeserialize(using = LocalDateDeserializer.class)
    @JsonSerialize(using = LocalDateSerializer.class)
    private LocalDate birthDate;
}

By implementing this approach, LocalDate objects can be serialized and deserialized effectively, enabling flexible JSON formatting.

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