What programming languages are supported?

This tool supports generating code from JSON for Java (POJO with Jackson/Gson annotations), TypeScript (interfaces and types), C# (classes with properties), Python (dataclasses and Pydantic models), Go (structs), and Kotlin (data classes).

How does JSON to Java conversion work?

The tool parses your JSON and generates Java POJO classes with appropriate field types. You can choose between Jackson or Gson annotations. Nested objects become separate inner classes, and arrays are converted to List types.

Can I convert nested JSON objects?

Yes, nested JSON objects are converted to nested classes or separate type definitions depending on the target language. The tool automatically detects nesting and creates the appropriate class hierarchy.

What is the difference between Pydantic and dataclass in Python?

Python dataclasses are built-in and simple, great for basic data containers. Pydantic models add runtime validation, type coercion, and serialization features. Use Pydantic for API models and data validation; use dataclasses for simpler internal data structures.

Is my JSON data sent to a server?

No, all conversion happens in your browser. Your JSON data never leaves your device. This tool is completely client-side for maximum privacy and speed.

JSON to Code Converter - Generate Classes from JSON Online

Target Language

Class/Interface Name

Input JSON

Paste JSON data or an array of objects. For arrays, the first item's structure will be used.

Generated Code (Java)

Generated code will appear here...

Supported Languages & Use Cases

Java

Spring Boot, REST APIs, microservices. Supports Jackson and Gson annotations.

TypeScript

Frontend apps, Node.js, type-safe API clients. Interface or type alias.

.NET APIs, ASP.NET Core. Class or record with JsonProperty attributes.

Python

FastAPI, Django, data processing. Dataclass or Pydantic BaseModel.

Go APIs, microservices. Struct with JSON tags for encoding/json.

Kotlin

Android apps, Kotlin Spring. Data class with optional Jackson annotations.

Protobuf

gRPC services, Protocol Buffers. Message definition with proto3 syntax.

What is JSON to Code Generator?

This tool converts JSON data into type-safe class definitions for multiple programming languages. It analyzes your JSON structure and generates appropriate fields, types, and annotations based on the target language. This is essential when working with REST APIs - instead of manually creating POJOs or interfaces, you can paste the API response and instantly get the code you need.

How to Use

Paste your JSON data into the input field. This can be a single object or an array of objects.
Select your target language (Java, TypeScript, C#, Python, Go, Kotlin, or Protobuf).
Enter a class/interface name for the generated code.
Configure language-specific options if needed (annotation style, builder pattern, etc.).
Click 'Generate Code' to create the type definition.
Copy the generated code or download it as a file for your project.

Why Use This Tool?

Save time - no need to manually write POJOs, interfaces, or structs

Reduce errors - automatic type inference ensures correct types

Consistent naming - proper conversion between JSON keys and language conventions

Flexible output - multiple annotation styles and code patterns

Works offline - all processing happens in your browser

Array support - automatically detects array structures and generates appropriate types

Tips & Best Practices

For Java Spring Boot projects, use Jackson annotations for proper serialization
Use the builder pattern for complex Java objects with many fields
For TypeScript frontend apps, use interface for API response types
Pydantic models are great for Python FastAPI projects with validation
Go structs with JSON tags work perfectly with encoding/json package
For Protobuf, use proto3 syntax for modern gRPC services
If your JSON has varying field types, consider making fields optional

Frequently Asked Questions

How does the tool handle JSON arrays?

When you provide a JSON array, the tool analyzes the first object in the array and generates a class/struct for that structure. This is useful for API responses that return lists of items - you get the correct type for each element.

What Java annotation styles are supported?

We support three styles: Jackson (@JsonProperty) for Spring Boot and most Java projects, Gson (@SerializedName) for Google's Gson library, and no annotations for simple cases where field names match JSON keys exactly.

Can I customize the generated code?

Yes! Each language has specific options: Java can include constructors, toString, and builder pattern; TypeScript can use type vs interface; C# can use record syntax; Python can use Pydantic; Go can include JSON tags; Protobuf supports proto3 syntax and package declaration.

How are types inferred from JSON values?

The tool examines each value: strings become String/str, numbers become Integer/int or Double/float depending on whether they have decimals, booleans become Boolean/bool, arrays become List/array types, and nested objects create separate type definitions.

Why use this instead of manual coding?

For APIs with complex responses, manually creating POJOs with 20+ fields is tedious and error-prone. This tool gives you correct types, proper annotations, and consistent naming in seconds. It's especially valuable when integrating with multiple APIs.

Is my JSON data secure?

Absolutely. All code generation happens entirely in your browser using JavaScript. Your JSON is never sent to any server, never stored, and never logged. This makes it safe for API responses containing sensitive data like user information or credentials.

JSON to Code Generator