How to model java.time.duration in Mysql Database

Question

I am writing a simple application to get to know Java EE, and I need to save an entity into my MySQL DB, which contains a java.time.duration.

What is the best way to store that?

Answer 1

As Hibernate 4.3 supports JPA 2.1 you can use the AttributeConverter class:

@Converter
public class DurationToStringConverter implements AttributeConverter<Duration, String>
{

    @Override
    public String convertToDatabaseColumn(Duration duration)
    {
        return duration == null ? null : duration.toString();
    }

    @Override
    public Duration convertToEntityAttribute(String dbData)
    {
        return dbData == null ? null : Duration.parse(dbData);
    }
}

@Entity
public class Ent {

    @Column
    @Convert(DurationToStringConverter.class)
    Duration duration;

}

See: http://docs.oracle.com/javaee/7/api/javax/persistence/Convert.html

Answer 2

Unfortunately, JPA still does not support the types of the new java.time package

That said, you have a couple of methods (toString and parse) that provide you a way by converting to String; v.g.

@Transient
private Duration myDuration;

@Column(name="DURATION")
String myDurationString;

@PostLoad
public void init() {
  this.myDuration = this.myDurationString == null ? null : Duration.parse(this.myDurationString);
};

public Duration getMyDuration() {
  return this.myDuration;
}

public void setMyDuration(Duration _myDuration) {
  this.myDurationString = _myDuration == null ? null : _myDuration.toString();
}

Remember that you should not include getters and getters for myDurationString.

Optionally, you could use toMillis() and ofMillis(), if you are more comfortable with the number as milliseconds.