`XmlMapper` is unable to deserialise into an empty record

[protazy]

It seems that deserialising into an empty record does not work correctly, however the same example with an "empty" class works just fine.

Here's a snippet of code to reproduce:

package org.example;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;

public class App {
    public static void main(String[] args) throws JsonProcessingException {
        XmlMapper mapper = XmlMapper.builder().build();

       // This works just fine, an empty class will deserialise correctly.
        EmptyClassTest emptyClassTest = mapper.readValue("<EmptyClassTest/>", EmptyClassTest.class);

       // This throws an exception.
        EmptyRecordTest emptyRecordTest = mapper.readValue("<EmptyRecordTest/>", EmptyRecordTest.class);
    }

    public static class EmptyClassTest {
    }

    public record EmptyRecordTest() {
    }
}

After executing the above code, an exception is thrown when trying to deserialise into an empty record:

Exception in thread "main" com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of org.example.App$EmptyRecordTest (although at least one Creator exists): no default no-arguments constructor found
 at [Source: (StringReader); line: 1, column: 1]
	at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
	at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1728)
	at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1353)
	at com.fasterxml.jackson.databind.deser.ValueInstantiator.createUsingDefault(ValueInstantiator.java:248)
	at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createUsingDefault(StdValueInstantiator.java:275)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.getEmptyValue(BeanDeserializerBase.java:1042)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer._deserializeFromEmptyString(StdDeserializer.java:322)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer._deserializeFromString(StdDeserializer.java:270)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromString(BeanDeserializerBase.java:1495)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:196)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:186)
	at com.fasterxml.jackson.dataformat.xml.deser.XmlDeserializationContext.readRootValue(XmlDeserializationContext.java:91)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4674)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3629)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3597)
	at org.example.App.main(App.java:14)

Tested with jackson-dataformat-xml version 2.13.1

[jsuryakt]

Is this issue solved?

[cowtowncoder]

@jsuryakt If it was there would be an update here so likely not.

But since it was reported against old version, you may want to try it against 2.18.3 or 2.19.0-rc2.

[cowtowncoder]

Ok, I went ahead and added a unit test: turns out issue HAS been fixed.
Updated release notes will indicate fix in 2.19.0 (since test added there), but I am pretty sure it was fixed in 2.18.0 already, so upgrade to 2.18.3 should resolve it.
(may have been fixed earlier but changes in 2.18.0 seem most likely as to fix)