When processing a Json string with XMLGregorianCalender using Gson I get the exception:
java.lang.RuntimeException: Failed to invoke public javax.xml.datatype.XMLGregorianCalendar() with no args
The object which is de-serialized by fromJson(..) with Gson has a XMLGregorianCalender object.
What can be the possible solution for the above error?
Abstract class javax.xml.datatype.XMLGregorianCalendar can not be a instantiated by its default/no-args constructor which makes GSON to fail.
If you resolve the class that extends above mentioned and that class has a public no-args constructor you can de-serialize that directly. For example, in my case:
XMLGregorianCalendar xmlGC = gson.fromJson(strXMLGC,
com.sun.org.apache.xerces.internal
.jaxp.datatype.XMLGregorianCalendarImpl.class);
A generic way to get it working everywhere - without caring the implementing class - is to define a custom JsonDeserializer. To make de-serialing easy you could first create an adapter class that holds the data that XMLGregorianCalendar's JSON has:
@Getter
public class XMLGregoriancalendarAdapterClass {
private BigInteger year;
private int month, day, timezone, hour, minute, second;
private BigDecimal fractionalSecond;
}
Data types of each field in above class are chosen to match one specific method for constructing XMLGregorianCalendar with javax.xml.datatype.DatatypeFactory.
Having above adapter class create a de-serialiazer like:
public class XMLGregorianCalendarDeserializer
implements JsonDeserializer<XMLGregorianCalendar> {
@Override
public XMLGregorianCalendar deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
// Easily parse the adapter class first
XMLGregoriancalendarAdapterClass ac =
new Gson().fromJson(json,
XMLGregoriancalendarAdapterClass.class);
try {
// Then return a new newXMLGregorianCalendar
// using values in adapter class
return DatatypeFactory.newInstance()
.newXMLGregorianCalendar(ac.getYear(), ac.getMonth(),
ac.getDay(), ac.getHour(),
ac.getMinute(), ac.getSecond(),
ac.getFractionalSecond(), ac.getTimezone());
} catch (DatatypeConfigurationException e) {
e.printStackTrace();
}
return null;
}
}
Using above you can construct GSON like:
Gson gson = new GsonBuilder().setPrettyPrinting()
.registerTypeAdapter(
XMLGregorianCalendar.class,
new XMLGregorianCalendarDeserializer() )
.create();
after which it is just:
XMLGregorianCalendar xmlGC2 =
gson.fromJson(json, YourClassHavingXMLGregorianCalendar.class);