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Auto-detection of constructor-based creator method skipped if there is an annotated factory-based creator method (regression from 2.11)

See original GitHub issue

Describe the bug First, I am not sure whether it’s a bug or expected behavior, but I just wanted to open an issue for my understanding. Prior to Jackson 2.12.0, it was possible to bind a Number (e.g., 42) to a single field DTO (see example code below). Now, it throws MismatchedInputException with this message:

Cannot construct instance of `jackson211$ExampleDto$Json` (although at least one Creator exists):
no int/Int-argument constructor/factory method to deserialize from Number value (42) at [Source: (String)"42"; line: 1, column: 1]

Version information 2.12.0

To Reproduce The code below can be used.

Some notes:

  • I used jbang to switch between versions easily.
  • The example Dto is the minimal version of an Immutables generated code.
  • Jackson 2.11.3 uses the private constructor to deserialize Number to Dto object.
/// usr/bin/env jbang "$0" "$@" ; exit $?
//DEPS com.fasterxml.jackson.core:jackson-annotations:2.12.0
//DEPS com.fasterxml.jackson.core:jackson-databind:2.12.0

// It prints `true` on 2.11.3.
////DEPS com.fasterxml.jackson.core:jackson-annotations:2.11.3
////DEPS com.fasterxml.jackson.core:jackson-databind:2.11.3

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import java.util.Objects;

public final class jackson211 {
    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();

    public static void main(String... args) throws JsonProcessingException {
        int version = 1;
        ExampleDto deserialize = OBJECT_MAPPER.readValue(String.valueOf(version), ExampleDto.class);
        System.out.println(new ExampleDto(version).equals(deserialize));

    static final class ExampleDto {
        private final int version;

        private ExampleDto(int version) {
            this.version = version;

        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            ExampleDto that = (ExampleDto) o;
            return version == that.version;

        public int hashCode() {
            return Objects.hash(version);

        @JsonCreator(mode = JsonCreator.Mode.DELEGATING)
        static ExampleDto fromJson(Json json) {
            return new ExampleDto(json.version);

        @JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.NONE)
        static final class Json {
            int version;
            boolean versionIsSet;

            public void setVersion(int version) {
                this.version = version;
                this.versionIsSet = true;

            public int getVersion() {
                throw new UnsupportedOperationException();

Expected behavior As I wrote at the beginning, I am not sure whether it’s a bug or expected behavior. If it’s a bug then, the example code should print true instead of throwing an exception.

Additional context N/A

Issue Analytics

  • State:closed
  • Created 3 years ago
  • Reactions:1
  • Comments:8 (5 by maintainers)

github_iconTop GitHub Comments

cowtowncodercommented, Dec 6, 2020

So, rewritten code in 2.12 (meant to work same way as before) had checks so that:

  • Only check for implicit (non-annotated) Constructors if neither annotated factory methods NOR annotated constructors found

but apparently logic earlier was

  • Only check for implicit (non-annotated) Constructors if no annotated constructors found

so that existence of annotated factory method was the difference. Will change code to use older logic, to try to keep backwards-compatibility. This is bit tricky going forward as definition is not very crisp, but seems like the right thing to do for now.

cowtowncodercommented, Dec 2, 2020

Ok thank you for verifying these aspects. It sounds like there is an unintended change in behavior here, and I hope to look into it when I get a chance.

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