How to Fix Jackson "No Creators, like default construct, exist" Error in Java Retrofit Deserialization

By the end of this page, you will understand what Jackson means by a Creator, why Retrofit surfaces this error during deserialization, and how to fix your Java model classes using a no-argument constructor, @JsonCreator, and @JsonProperty when needed.

Jackson converts JSON into Java objects by creating an instance of your class and then filling in its fields or calling its constructor parameters.

That error means Jackson received a JSON object like this:

{
  "id": 1,
  "name": "Alice"
}

but it could not figure out how to create the Java object first.

In Jackson, a Creator is a way to build an object during deserialization. Common options are:

• a public no-argument constructor
• a constructor annotated with @JsonCreator
• constructor parameters annotated with @JsonProperty
• a builder pattern configured for Jackson

If your class only has a constructor with parameters and no default constructor, Jackson often cannot instantiate it automatically unless you explicitly tell it how.

This matters in real programming because API clients depend on reliable mapping between JSON responses and Java classes. If your models are not deserialization-friendly, network calls may succeed but object mapping will fail.

Think of Jackson as a delivery worker bringing JSON data to your Java class.

• The JSON is the package.
• Your Java class is the apartment.
• Jackson must first get inside the apartment before placing the items.

If the apartment has an unlocked front door, that is like a no-argument constructor.

If the apartment requires a special entry code, that is like a constructor with parameters. Jackson needs clear instructions about which values go where. Those instructions are provided with @JsonCreator and @JsonProperty.

Without a door or instructions, Jackson stands outside and throws the "No Creators" error.

Basic fix: add a no-argument constructor

If your class uses mutable fields or setters, the simplest fix is often to add a default constructor.

public class User {
    private int id;
    private String name;

    public User() {
        // Default constructor required by Jackson
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Jackson can now:

1. call new User()
2. set id
3. set name

Alternative fix: use

Consider this JSON response:

{
  "id": 10,
  "name": "Maya"
}

And this Java class:

public class User {
    private int id;
    private String name;

    public User() {
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

What Jackson does:

This issue appears often in API-driven Java applications.

Mobile or Android apps using Retrofit

A request succeeds, but parsing fails because the response model has only custom constructors.

Backend services consuming other APIs

A service calls an external API and maps the result into DTOs. If the DTOs are immutable but not annotated correctly, deserialization breaks.

JSON config loading

Applications often load JSON configuration into Java objects. Jackson still needs a valid way to create each object.

Data transfer objects in layered apps

Controllers, services, and clients often use DTO classes. These classes must be designed with serialization and deserialization in mind.

In real projects, developers usually choose one of these patterns:

1. Mutable DTOs with no-arg constructors

Common in simple apps and generated models.

public class ProductDto {
    private String sku;
    private double price;

    public ProductDto() {}

    public String getSku() { return sku; }
    public void setSku(String sku) { this.sku = sku; }

    public double getPrice() { return price; }
    public void setPrice(double price) { this.price = price; }
}

2. Immutable DTOs with @JsonCreator

Common when developers want safer objects.

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;

   {
      String sku;
       price;

    
      {
        .sku = sku;
        .price = price;
    }

     String  {  sku; }
       {  price; }
}

1. Only defining a parameterized constructor

This is the most common cause.

Broken

public class User {
    private int id;
    private String name;

    public User(int id, String name) {
        this.id = id;
        this.name = name;
    }
}

Fix

• add a no-argument constructor, or
• annotate the constructor with @JsonCreator and @JsonProperty

2. Missing getters and setters for mutable classes

If Jackson relies on setters and they do not exist, field population may fail.

public class User {
    private int id;
}

Safer version:

public class User {
    private int id;

      {}

       {
         id;
    }

       {
        .id = id;
    }
}

// Option 1: mutable class
public class User {
    private int id;
    private String name;

    public User() {}

    public int getId() { return id; }
    public void setId(int id) { this.id = id; }

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
}

// Option 2: immutable class
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;

public class User {
    private final int id;
    private final String name;

    @JsonCreator
      {
        .id = id;
        .name = name;
    }

       {  id; }
     String  {  name; }
}

Why does Jackson say "No Creators"?

Jackson cannot find a valid way to create an instance of your class during deserialization.

Do I always need a default constructor?

No. You can also use a constructor annotated with @JsonCreator and parameter names annotated with @JsonProperty.

Why does this happen in Retrofit onFailure?

Retrofit uses Jackson to parse the response. If parsing fails, the call may end up in the failure path depending on your adapter and converter setup.

Can private fields still be deserialized?

Yes, often they can, especially with getters/setters or Jackson configuration. But the object still needs a valid creation method.

What if my JSON field names are different from my Java fields?

Use @JsonProperty("json_name") to map them correctly.

Does this error mean the API response is invalid?

Not always. The JSON may be perfectly valid, but your Java class may not be compatible with Jackson deserialization.

Should I use mutable or immutable DTOs?

Both are valid. Mutable DTOs are simpler for beginners. Immutable DTOs are safer and often preferred in larger codebases.

• JSON deserialization — This is the direct process Jackson is performing when converting API responses into Java objects.
• Retrofit converters — Retrofit relies on converters like Jackson to map HTTP response bodies into model classes.
• POJO classes — Plain Java objects are commonly used as API response models.
• @JsonProperty — This annotation maps JSON field names to Java constructor parameters or fields.
• @JsonCreator — This annotation tells Jackson which constructor or factory method to use.
• DTO (Data Transfer Object) — API responses are often represented as DTOs designed for serialization and deserialization.
• Immutable objects — Constructor-based deserialization is closely related to immutable class design.
• Serialization vs deserialization — Understanding the difference helps when working with APIs and JSON mapping.