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Map deserialization results in different numeric classes based on json ordering (BigDecimal / Double) when used in combination with @JsonSubTypes

See original GitHub issue

Describe the bug When deserializing a jsonSubTye which contains a map with numeric values (floats) the order of the json string results in different classes constructed.

I have pasted a complete Junit5 Test which can easily be used to reproduce the issue.

Version information Happens from 2.12.0 onwards, in 2.11.x its ok.

To Reproduce If you have a way to reproduce this with:

package test;

import java.util.HashMap;
import java.util.Map;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInstance;
import org.junit.jupiter.api.TestInstance.Lifecycle;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonSubTypes.Type;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JacksonSubTypeBehaviourTest {

	private static final Logger log = LoggerFactory.getLogger(JacksonSubTypeBehaviourTest.class);

	private ObjectMapper mapper;

	public void before() {
		mapper = new ObjectMapper();

	public void testDeserializeWithDifferentOrdering() throws Exception {
		String ordering1 = "{\n"
				+ "			\"type\": \"MAP\",\n"
				+ "			\"map\": {\n"
				+ "				\"doubleValue\": 0.1\n"
				+ "			}\n"
				+ "}";
		TestMapContainer model1 = mapper.readValue(ordering1, TestMapContainer.class);"clazz: {}",  model1.getMap().get("doubleValue").getClass());
		Assertions.assertTrue(model1.getMap().get("doubleValue") instanceof Double);
		String ordering2 = "{\n"
				+ "	\"map\": {\n"
				+ "		\"doubleValue\": 0.1\n"
				+ "	},\n"
				+ "	\"type\": \"MAP\"\n"
				+ "	\n"
				+ "}";
		TestMapContainer model2 = mapper.readValue(ordering2, TestMapContainer.class);"clazz: {}",  model2.getMap().get("doubleValue").getClass());
		Assertions.assertTrue(model2.getMap().get("doubleValue") instanceof Double);
		    use = JsonTypeInfo.Id.NAME,  
		    include = JsonTypeInfo.As.PROPERTY,  
		    property = "type")

	    @Type(value = TestMapContainer.class, name = "MAP"),
	private static interface TestJsonTypeInfoInterface {
	private static class TestMapContainer implements TestJsonTypeInfoInterface {
		private Map<String, ? extends Object> map = new HashMap<>();

		public Map<String, ? extends Object> getMap() {
			return map;

		public void setMap(Map<String, ? extends Object> map) { = map;

Expected behavior Numeric values (point numbers) should always be created as Double unless stated otherwise with DeserializationFeature.USE_BIG_DECIMAL_FOR_FLOATS

Issue Analytics

  • State:open
  • Created 2 years ago
  • Comments:9 (5 by maintainers)

github_iconTop GitHub Comments

cowtowncodercommented, Oct 9, 2021

The difference is meant to defer possible truncation/coercion in case of buffering (since we have no idea what the target type is); whereas when using UntypedObjectDeserializer – which has target type of java.lang.Object – we know what target type we should be using, based on configuration.

This matter more for binary formats where there is specific accurate representation, but is more problematic for textual formats that do not have distinction between various FP representations. And then there is the difference between streaming-level and databind-level configuration to consider too.

Ideally, I think, the whole decoding should be deferred in buffering cases: parser would simply validate that the textual representation is valid JSON (or xml, yaml, csv etc) Number, but would not try to get Java Number out of it until explicitly requested.

cowtowncodercommented, Oct 18, 2022

@mreiterer I don’t think so due to timing constraints.

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