Deserializer to Java LocalDateTime

[lmajano]

I now know how to create custom deserializer. However, I can't seem to pin point how to create one to convert a json iso8601 string to a Java LocalDate time object.

Here is a portion of my ReaderWriterProvider

/**
* Custom BoxLang Deserializers by type
*/
@Override
public ValueReader findValueReader( JSONReader readContext, Class<?> type ) {
  // Java Date Times
  if ( type == LocalDate.class || type == Date.class || type == java.sql.Date.class ) {
	return new JavaDateTimeJsonDeserializer();
  }

  // All Map types funneled through Struct
  if ( type.isAssignableFrom( Map.class ) ) {
	return new StructJsonDeserializer();
  }

  // All Lists funneled through Array
  if ( type.isAssignableFrom( List.class ) ) {
	return new ArrayJsonDeserializer();
  }

  return null;
}

However, it seems jackson jr, is ALWAYS treating iso8601 date/times as just strings and leaves the item as a string.

[cowtowncoder]

I'd need a reproduction of the issue including how you are invoking read, wrt Date types. And even more importantly, how are you registering your ValueReaders?

As to List and Map: they must be registered differently; Class is not enough to pass type -- there is a way to override deserialization but not quite the same way as for non-generic type.

[lmajano]

Sure. Here are the relevant pieces.

Story

If a JSON packet contains an iso8601 date/time deserialize it to a Java LocalDateTime

Sample JSON

{
  "string" : "boxlang",
  "numeric" : 1,
  "float" : 41.1,
  "struct" : { "one" : "wood" },
  "array" : [1,2,3],
  "date" : "2022-10-31",
  "dateTime": "2022-10-31T09:00:00.594Z",
  "dateTime2": "2022-10-31T09:00:00Z"
}

Builder

Here is how we build our builder for our app:

/**
	 * The JSON builder library we use
	 */
	private static final JSON JSON_BUILDER = JSON.builder(
	    // Use a custom factory with enabled parsing features
	    new JsonFactory()
	        .enable( JsonParser.Feature.ALLOW_COMMENTS )
	        .enable( JsonParser.Feature.ALLOW_YAML_COMMENTS )
	)
	    // Enable JSON features
	    // https://fasterxml.github.io/jackson-jr/javadoc/jr-objects/2.8/com/fasterxml/jackson/jr/ob/JSON.Feature.html
	    .enable(
	        JSON.Feature.PRETTY_PRINT_OUTPUT,
	        JSON.Feature.USE_BIG_DECIMAL_FOR_FLOATS,
	        JSON.Feature.USE_FIELDS,
	        JSON.Feature.WRITE_NULL_PROPERTIES
	    )
	    // Add Jackson annotation support
	    .register( JacksonAnnotationExtension.std )
	    // Add JavaTime Extension
	    .register( new JacksonJrJavaTimeExtension() )
	    // Add Custom Serializers/ Deserializers
	    .register( new JacksonJrExtension() {

		    @Override
		    protected void register( ExtensionContext extensionContext ) {
			    extensionContext.insertProvider( new BoxJsonProvider() );
		    }

	    } )
	    // Yeaaaahaaa!
	    .build();

Our BoxJson Provider

/**
	 * Custom BoxLang Serializers by type
	 */
	@Override
	public ValueWriter findValueWriter( JSONWriter writeContext, Class<?> type ) {

		if ( type == DateTime.class || type == LocalDate.class || type == Date.class || type == java.sql.Date.class ) {
			return new DateTime();
		}

		if ( IClassRunnable.class.isAssignableFrom( type ) ) {
			return new BoxClassSerializer();
		}

		if ( type == DynamicObject.class ) {
			return new DynamicObjectSerializer();
		}

		return null;
	}

	/**
	 * Custom BoxLang Deserializers by type
	 */
	@Override
	public ValueReader findValueReader( JSONReader readContext, Class<?> type ) {

		// DateTime Objects
		if ( type.equals( DateTime.class ) ) {
			return new DateTimeDeserializer();
		}

		// Java Date Objects
		if ( type.equals( LocalDate.class ) ) {
			return new LocalDateDeserializer();
		}

		// Java DateTime Objects
		if ( type.equals( java.time.LocalDateTime.class ) ) {
			return new LocalDateTimeDeserializer();
		}

		// All Map types funneled through Struct
		if ( type.isAssignableFrom( Map.class ) ) {
			return new StructDeserializer();
		}

		// All Lists funneled through Array
		if ( type.isAssignableFrom( List.class ) ) {
			return new ArrayDeserializer();
		}

		return null;
	}

LocalDateTimeDeserializer

public class LocalDateTimeDeserializer extends ValueReader {

	/**
	 * Constructor
	 */
	public LocalDateTimeDeserializer() {
		super( LocalDateTime.class );
	}

	@Override
	public Object read( JSONReader reader, JsonParser jsonParser ) throws IOException {
		return DateTimeCaster.cast( jsonParser.getText() );
	}

}

[cowtowncoder]

Quick not on Map and List reader registration: callbacks called for those would be:

    public ValueReader findCollectionReader(JSONReader readContext, Class<?> type,
            ResolvedType valueType, ValueReader readerForValues);

    public ValueReader findMapReader(JSONReader readContext, Class<?> type,
            ResolvedType valueType, ValueReader readerForValues);

in which element/value readers are passed in to be optionally used by custom readers.
They cannot be registered via regular findValueReader() callback.

As to date/time classes, I think what'd be needed is really a self-contained unit test just for one types: I suspect that whatever is the problem it applies to all types.
There are tests for custom value readers (com.fasterxml.jackson.jr.ob.impl.CustomValueReadersTest, com.fasterxml.jackson.jr.ob.impl.CustomValueWritersTest) but they are not very complete