Jackson Custom Serialization Sample2.md

Use Case:

• A third party library is responsible for serializing or deserializing the object eg. custom serialization of api response contracts in a spring webapplication. i.e the ObjectMapper cannot be accessed and configured directly
• We want to serialize instances of only one class.

How am I doing it

• Using @JsonSerialize at class level to register a custom serializer for instances of that class.

my-custom-serializer

/*
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######### IF YOU FOUND THIS GIST USEFUL, PLEASE LEAVE A STAR. THANKS. ############
##################################################################################
##################################################################################
*/

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

import java.io.IOException;
import java.time.ZoneOffset;

public class EventSerializer extends JsonSerializer<Event> {

  @Override
  public void serialize(Event event, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {

    jsonGenerator.writeStartObject();
    jsonGenerator.writeStringField("name", event.getName());

    String startDateWithZone = event.getStartDate().atZone(ZoneOffset.UTC).toString();
    jsonGenerator.writeStringField("startDate", startDateWithZone);

    String endDateWithZone = event.getEndDate().atZone(ZoneOffset.UTC).toString();
    jsonGenerator.writeStringField("endDate", endDateWithZone);

    jsonGenerator.writeEndObject();
  }

}

object-to-serialize

@JsonSerialize(using = EventSerializer.class)
public class Event {
  private String name;

  private LocalDateTime startDate;

  private LocalDateTime endDate;

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public LocalDateTime getStartDate() {
    return startDate;
  }

  public void setStartDate(LocalDateTime startDate) {
    this.startDate = startDate;
  }

  public LocalDateTime getEndDate() {
    return endDate;
  }

  public void setEndDate(LocalDateTime endDate) {
    this.endDate = endDate;
  }
}

usage

Event event = new Event();
event.setName("someEvent");
event.setStartDate(LocalDateTime.now());
event.setEndDate(LocalDateTime.now().plusDays(1));

System.out.println(new ObjectMapper().writeValueAsString(event));