Serialize and Deserialize Date to Bean in Java - json

Question

I've to projects: an API Rest named Usuario and a JEE Application named store. Store gets the information to work from the Usuario API.
All the information is sent and received using MediaType.APPLICATION_JSON_TYPE.
In the API there's the Evento entity, which has the next attribute: Date fecha.
In the JEE Application there's the Evento bean, which has the next attribute: Date fecha.
When the API sends any object of the Evento class, it sends the Date with the format yyyy-MM-dd HH:mm: {"Date":"2017-12-06 23:02"}.
The JEE Application uses Client and WebTarget to use de API and get the information.
The problem here is that fecha (of type Date) in the evento object is null. It's not well-deserialized.
I can not use Spring on the JEE Application.I'm using JAX-RS in the store application.
Could you help me, please?

Answer 1

Let's clarify some facts, first. (I'm not 100% sure, though.)
There is no standard rule for representing dates or instants in JSON.
Some uses millisecons while others some formatted strings such as ISOZ.
There is no standard rule for serializing/deserializing in Java EE.
It only works as underlying message provider for application/json.
Note that JSON-B may not available in the spec yet.
Let's say we have this entity.
// I really want to know what Evento/fatcha means.
// Are they Italian words?
#XmlRootElement
#Entity
public class Evento implements Serializable {
public Date getFetcha() {
return ofNullable(fetcha)
.map(v -> new Date(v.getTime()))
.orElse(null);
}
public void setFetcha(final Date fetcha) {
this.fetcha = ofNullable(fetcha)
.map(v -> new Date(v.getTime()))
.orElse(null);
}
#XmlElement
#Temporal(TIMESTAMP)
private Date fetcha;
}
Now we can't help but depends on the underlying MessageReader or MessageWriter for serializing/deserializing in application/json.
Jackson will work in some way while MOXy will work in its way.
The only way to push client is that, they should use the format exactly as the same format when they GET the resource.
One way that I use is using another property for unified formatting/parsing.
#XmlRootElement
#Entity
public class Evento implements Serializable {
// ...
#JsonProperty
#JsonbProperty
#XmlElement
public String getFetchaIsoz() {
return ofNullable(getFetcha())
.map(Date::toInstant)
.map(DateTimeFormatter.ISO_INSTANT:format)
.orElse(null);
}
public void setFetchaIsoz(final String fetchaIsoz) {
setFetcha(ofNullable(fetchaIsoz)
.map(DateTimeFormatter.ISO_INSTANT:parse)
.map(Instant::from)
.map(Date::from)
orElse(null));
}
#JsonIgnore // just in case, e.g. Spring?
#JsonbTransient
#XmlTransient
#Temporal(TIMESTAMP)
private Date fetcha;
}
Not we have an alternative property which guarantees to work in specific format.