Overcoming the Drawbacks of Official Flutter JSON Serialization with json_entity

Thanh Tùng Phạm — Sun, 21 Sep 2025 17:47:17 +0000

As a Flutter developer, one of the common challenges you face is efficient and maintainable JSON serialization. The official Flutter JSON serialization mechanism offers a solution, but it comes with its own set of drawbacks. In this blog post, we'll discuss these drawbacks and introduce json_entity, an alternative JSON serialization library developed by the TrueSight team, which aims to address these issues.

Drawbacks of Official Flutter JSON Serialization

1. File Explosion

Issue:
With the official JSON serialization approach, each model source file generates a corresponding .g.dart file for the generated code. In large projects with numerous model files, this can lead to a significant increase in the number of files, making the project structure cumbersome and harder to manage.

Example:
Imagine working on a project with 500 model files. You would end up with 1000 files (500 model files + 500 generated files). This proliferation of files can clutter the project, making navigation and management a nightmare. It also complicates version control, code reviews, and collaborative development.

2. Re-running Code Generators

Issue:
Every time you make changes to a model, you need to re-run the code generator to update the generated files. For large projects, this process can be time-consuming and disrupt the development workflow.

Example:
In a project with 500 models, a minor change in one model requires re-running the code generator for all models. This can take a significant amount of time, especially in CI/CD pipelines, slowing down the entire development process. Developers often find themselves waiting for the code generation to complete, hampering productivity.

3. Increased IDE Resource Consumption

Issue:
The sheer number of generated files in large projects can lead to increased resource consumption by the IDE. This can result in slower code completion, suggestions, and overall reduced development efficiency.

Example:
When your project contains thousands of files, the IDE needs to index and manage all these files. This can slow down auto-completion and other IDE features, making coding sluggish and frustrating. The increased memory usage can also lead to frequent crashes or the need for high-end hardware, adding to development costs.

Introducing json_entity

To address these challenges, the TrueSight team has developed json_entity, a library designed to streamline JSON serialization and enhance overall project management. Here's a look at how json_entity can help overcome the drawbacks mentioned above.

Key Features of json_entity

Convenient JSON Serialization with Auto Mapper: Simplifies the process of mapping JSON to Dart objects and vice versa.
Custom Filters for Backend Integration: Provides an easy way to create and manage filters for querying backend data.
Built-in HTTP Request Management: Comes with an HTTP repository pattern to handle API requests efficiently.
Integration with go_router for Routing: Supports the go_router package for managing routes in your application.

Getting Started with json_entity

To install json_entity, run the following command:

flutter pub add json_entity go_router intl

JSON Serialization with json_entity

Defining a JsonModel

In json_entity, each model extends the JsonModel class. Here's an example of defining an AppUser model:

class AppUser extends JsonModel {
  @override
  List<JsonField> get fields => [
    username,
    password,
    email,
    isAdmin,
    dateOfBirth,
    age,
    level,
    manager,
    members,
  ];

  JsonString username = JsonString('username', isRequired: false, helper: 'Username of the user');
  JsonString password = JsonString('password', isRequired: false, helper: 'Password of the user');
  JsonString email = JsonString('email', isRequired: false, helper: 'Email of the user');
  JsonBoolean isAdmin = JsonBoolean('isAdmin', isRequired: false, helper: 'Is the user an admin');
  JsonDate dateOfBirth = JsonDate('dateOfBirth', isRequired: false, helper: 'User\'s date of birth');
  JsonInteger age = JsonInteger('age', isRequired: false, helper: 'Age of the user');
  JsonDouble level = JsonDouble('level', isRequired: false, helper: 'Level of the user');
  JsonObject<AppUser> manager = JsonObject('manager', isRequired: false, helper: 'Manager of the user');
  JsonList<AppUser> members = JsonList<AppUser>('members', isRequired: false, helper: 'Members that this user manages');
}

Mapping Data from JSON

To map data from JSON:

final json = await requestFromAPI();
AppUser user = AppUser();
user.fromJSON(json);

Converting to JSON

To convert a model to JSON:

AppUser user = AppUser();
user.toJSON(); // Returns the JSON representation of the user as a Dart Map object.
user.toString(); // Returns the JSON representation of the user as a Dart String.

Conclusion

While the official Flutter JSON serialization mechanism is functional, it has notable drawbacks, especially in large projects. json_entity offers an alternative that addresses these issues by reducing the number of files, eliminating the need for frequent code generator runs, and improving IDE performance. json_entity enhances the development experience and boosts productivity.

If you are working on a large Flutter project and facing challenges with JSON serialization, give json_entity a try. It might be the solution you've been looking for to streamline your development workflow and improve your project's maintainability.

DEV Community: Thanh Tùng Phạm