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Convert JSON to Java POJO classes with proper getters, setters, and annotations. Support for Jackson, Gson, and Lombok. Perfect for API integration, data models, and Android development.
Everything you need to know about converting JSON to Java POJO classes
I've been a Java developer for over 12 years. Spring Boot, Android, microservices — you name it, I've built it. And one thing that has always annoyed me? Manually writing POJO classes for JSON APIs.
You get a new API endpoint. The response has 25 fields, nested objects, arrays. Suddenly you're spending 30 minutes writing Java classes. Adding getters. Setters. Constructors. JSON annotations. Every. Single. Time.
That's why I built this JSON to Java POJO converter. After a particularly painful week where I had to map 8 different APIs with complex nested structures, I decided there had to be a better way. This tool is the result — and it's saved me countless hours since.
// JSON Input
{
"id": 123,
"name": "John Doe",
"email": "john@example.com",
"isActive": true
}
// Generated Java POJO (with Lombok)
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class User {
private Integer id;
private String name;
private String email;
private Boolean isActive;
}
POJO stands for "Plain Old Java Object". It's a Java object that doesn't extend or implement any special classes or interfaces. In modern Java development, POJOs are used everywhere:
Understanding how JSON types map to Java types is crucial for correct deserialization. Here's the complete mapping our converter uses:
| JSON Type | Java Type | Wrapper Class | Example | Notes |
|---|---|---|---|---|
| string | String | String | "John Doe" | Use String for text data |
| integer | int | Integer | 42 | int for primitive, Integer for nullable |
| number | double | Double | 29.99 | double for primitive, Double for nullable |
| boolean | boolean | Boolean | true/false | boolean for primitive, Boolean for nullable |
| array | List<T> | List<T> | [1, 2, 3] | Use List with generic type |
| object | Custom class | Custom class | {"key": "value"} | Nested POJO class |
| null | Object | Object | null | Use wrapper classes |
Jackson is the most popular JSON library for Java. It's used by Spring Boot by default and offers excellent performance. Our converter can add Jackson annotations:
import com.fasterxml.jackson.annotation.JsonProperty;
public class User {
@JsonProperty("user_id")
private Integer userId;
@JsonProperty("user_name")
private String userName;
}
Gson is another popular choice, especially in Android development. It's lightweight and easy to use:
import com.google.gson.annotations.SerializedName;
public class User {
@SerializedName("user_id")
private Integer userId;
@SerializedName("user_name")
private String userName;
}
Lombok isn't a JSON library, but it reduces Java boilerplate dramatically. With Lombok, you don't need to write getters, setters, constructors, or toString methods:
import lombok.Data;
import lombok.Builder;
import lombok.NoArgsConstructor;
import lombok.AllArgsConstructor;
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class User {
private Integer id;
private String name;
private String email;
}
I've done this both ways hundreds of times. Here's the real difference:
Manual Process for a medium API response (15 fields, nested objects):
Automated Process with this converter:
When building REST APIs with Spring Boot, you need POJOs for request bodies and response bodies. Our converter generates exactly what you need:
@PostMapping("/users")
public ResponseEntity createUser(@RequestBody CreateUserRequest request) {
User user = userService.createUser(request);
return ResponseEntity.ok(user);
}
Android apps constantly consume JSON from REST APIs. Use our converter to generate POJOs that work with Retrofit, Volley, or OkHttp:
public interface ApiService {
@GET("users/{id}")
Call getUser(@Path("id") int userId);
}
Microservices often communicate via JSON messages. Generate POJOs for your message contracts once, share them across services.
When processing JSON data from Kafka, SQS, or file sources, you need POJOs to deserialize the data. Generate them instantly from example messages.
Integrating with Stripe, GitHub, Twitter, or any other API? Paste their JSON response examples, get Java POJOs instantly.
Our converter follows Java standard naming conventions:
One of the biggest challenges in JSON deserialization is handling nested objects. Our converter automatically generates nested static classes:
// JSON with nested address
{
"user": {
"name": "John",
"address": {
"street": "123 Main St",
"city": "Boston"
}
}
}
// Generated Java classes
public class User {
private String name;
private Address address;
public static class Address {
private String street;
private String city;
// getters and setters
}
}
JSON arrays become Java List<T> with proper generic types:
// JSON array of objects
{
"users": [
{"id": 1, "name": "John"},
{"id": 2, "name": "Jane"}
]
}
// Generated Java
public class UserList {
private List<User> users;
}
Java 14 introduced Records — immutable data carriers that replace traditional POJOs for simple data holders:
// Traditional POJO (many lines)
public class User {
private String name;
private String email;
// constructor, getters, setters, equals, hashCode, toString
}
// Java Record (one line!)
public record User(String name, String email) {}
Our converter can generate Records instead of traditional classes for immutable data models.
Use Integer instead of int, Boolean instead of boolean when fields can be null in JSON.
@JsonProperty for Jackson, @SerializedName for Gson ensure correct field name mapping.
Use final fields and constructor parameters for immutable objects. Better thread safety and predictability.
Lombok's @Data, @Builder, @NoArgsConstructor reduce code by 60-70%.
For objects used in collections or comparisons, proper equals/hashCode implementation is essential.
ObjectMapper mapper = new ObjectMapper()
.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, true);
This catches API changes early.
If a JSON field can be null, use Integer instead of int, Boolean instead of boolean. Otherwise, you'll get NullPointerException.
Many JSON libraries need a no-argument constructor for deserialization. Lombok's @NoArgsConstructor solves this.
Always create nested classes for nested JSON objects. Our converter does this automatically.
Use @JsonProperty to map JSON field names (snake_case) to Java field names (camelCase).
POJO is any plain Java object. JavaBean is a POJO with specific conventions: no-arg constructor, getters/setters, serializable. Our converter generates JavaBeans by default.
Jackson is more feature-rich and faster. Gson is simpler and has smaller footprint. Spring Boot uses Jackson by default. Android often uses Gson or Moshi.
Yes! Millions of projects use Lombok. It's compile-time only, no runtime overhead. Just add the plugin to your IDE.
Absolutely! Generate POJOs for Retrofit, Volley, or OkHttp. Use Gson or Moshi for deserialization.
Date strings become String fields. You can manually add Date types with @JsonFormat for Jackson or custom deserializers.
Yes! All conversion happens in your browser. Your JSON never leaves your device. We don't store, process, or transmit your data to any server.
Transform your JSON into Java classes in just a few clicks
Enter Your JSON Paste your JSON data, upload a .json file, or click on any example. Our editor supports syntax highlighting and auto-formatting.
Configure Options Choose your annotations (Jackson, Gson, or none), select Lombok support, set package name, and customize class naming.
Click Convert Hit the Convert button or use ⌘+Enter (Ctrl+Enter). Our parser analyzes your JSON and generates Java POJO classes.
Copy or Download Copy the generated code to your clipboard or download as a .java file. Use it immediately in your Java project.
Everything you need to generate production-ready Java POJOs
How developers use JSON to Java POJO Converter
Stop writing Java classes manually. Generate them instantly from JSON and focus on your business logic.
Eliminate manual type mapping mistakes. Our generator creates accurate Java types that match your data.
Your JSON never leaves your browser. No server uploads, no tracking, complete privacy.
Perfect for beginners learning Java. See how JSON structures translate to well-designed Java classes.
Generate classes for REST APIs, GraphQL responses, or any JSON data source with proper annotations.
Generated code follows Java best practices and is ready to use in production.
Automatic Lombok annotations mean less boilerplate and cleaner code.
No installation required. Use it directly in your browser, anywhere, anytime.
Everything you need to know about JSON to Java POJO conversion
JSON to Java POJO converter is a developer tool that automatically transforms JSON data into Java class definitions. It analyzes your JSON structure and generates accurate Java code with proper types, getters, setters, and JSON annotations.
Yes, completely free! No signup required, no hidden costs, and no limitations on usage. I built this because I needed it myself, and I believe developer tools should be accessible to everyone.
Generated code is compatible with Java 8 and above. For Records feature, Java 14+ is required.
Yes! You can enable Jackson annotations (@JsonProperty) for field name mapping. This is especially useful for snake_case JSON to camelCase Java fields.
Yes! The converter can add Gson @SerializedName annotations for field name mapping.
Absolutely! Enable Lombok support to generate @Data, @Builder, @NoArgsConstructor, and @AllArgsConstructor annotations instead of manual getters/setters.
Nested JSON objects become nested static inner classes. This keeps your code organized and prevents class name conflicts.
JSON arrays become Java List<T> with proper generic types. This works with Jackson, Gson, and all major JSON libraries.
Yes! Fields that can be null in JSON become wrapper types (Integer, Boolean, Double) instead of primitives (int, boolean, double).
Yes! Your data never leaves your browser. All conversions happen locally on your device. We don't store, process, or transmit your JSON data to any server.
Yes! The generated Java code follows best practices and is production-ready. Review and add any additional validation or business logic as needed.
Our tool can handle JSON files up to 10MB efficiently. For larger files, we recommend splitting them into smaller chunks.