Json2POJOJson2POJO
Reverse Converter

Convert POJO to JSON Online

Instantly generate Mock JSON Data from your Java classes. Perfect for creating test payloads, seeding databases, or providing frontend mocks.

Java Class (Input)

Generated JSON (Realistic Mock)

How it Works: Smart Mocking

Most converters just output "string_value". We are smarter. Our engine analyzes your field names to generate Realistic Data for better testing:

Field Name (Input)Generated Value (Output)
private String email;"jane.doe@example.com"
private UUID id;"550e8400-e29b-41d4..."
private String avatar;"https://example.com/..."
private Date createdAt;"2025-01-01T12:00:00Z"

How to Generate JSON from Java Class

  1. Paste your Java Code

    Copy your full Java class definition (e.g., public class UserDTO ...) into the left input box. We support fields with or without Lombok annotations.

  2. Automatic Parsing

    Our intelligent parser identifies field names (userId) and types (Long). It handles Lists, Maps, and nested objects automatically.

  3. Copy the JSON

    The tool generates a valid JSON object populated with dummy data. Click the Green Copy Button to use this payload in Postman, Swagger, or your Unit Tests.

What is a POJO?

POJO stands for "Plain Old Java Object". It is a fundamental concept in Java development, representing a simple object with no dependencies on specific frameworks (like EJB).

In modern web development, POJOs are often used as DTOs (Data Transfer Objects) to map database entities to JSON responses for REST APIs.

Why Mock Data Matters?

When building a Spring Boot backend, you often need to test your @RequestBody parsing without writing manual JSON.

This tool automates that via Reverse Engineering. Instead of typing brackets and quotes manually (which is error-prone), you use your single source of truth: the Java Class.

Java POJO to JSON with ObjectMapper

In production Java applications, you'll use Jackson's ObjectMapper to convert POJO to JSON string. Here's the standard approach:

// Jackson ObjectMapper - POJO to JSON
ObjectMapper mapper = new ObjectMapper();

// Convert POJO to JSON String
String json = mapper.writeValueAsString(userPojo);

// Pretty print with indentation
String prettyJson = mapper.writerWithDefaultPrettyPrinter()
    .writeValueAsString(userPojo);

Convert POJO to JSON using Gson

Gson is Google's JSON library, popular in Android development. Converting POJO to JSON with Gson is straightforward:

// Gson - POJO to JSON
Gson gson = new Gson();
String json = gson.toJson(userPojo);

// Pretty print with GsonBuilder
Gson prettyGson = new GsonBuilder()
    .setPrettyPrinting().create();
String prettyJson = prettyGson.toJson(userPojo);

✅ When to use Jackson

Spring Boot apps, enterprise systems, streaming large files, advanced customization

✅ When to use Gson

Android apps, simple projects, when you want minimal dependencies

Troubleshooting & Tips

Empty Output?

Ensure your fields have types defined.
Example: name; (Invalid) vs String name; (Valid).

Generics Support

We support complex generics like Map<String, List<User>>. These will be converted into nested JSON objects/arrays.

Lombok @Data

You do not need to delete Lombok annotations. Our parser ignores lines starting with @ and focuses on field definitions.