What is JSON to Java POJO Generator?

This tool converts JSON data into Java POJO (Plain Old Java Object) classes with optional Jackson annotations. It automatically infers types, handles nested objects as separate classes, supports List and Optional types, and generates complete Java code with constructors, getters, and setters.

How to Use

Set the root class name and configure options (Jackson annotations, date detection, Optional, getters/setters)
Paste your JSON data into the input area
Click "Generate Java POJO" and copy the output into your project

Why Use This Tool?

Automatically infer Java types from JSON values

Generate Jackson @JsonProperty annotations for camelCase field mapping

Detect ISO-8601 date strings and map them to Instant/LocalDate types

Generate nested classes with correct ordering

Support Optional<T> for nullable fields

Generate complete POJOs with constructors, getters, and setters

Tips & Best Practices

Use realistic sample data — type inference depends on actual values
Enable Jackson annotations for seamless JSON serialization/deserialization
@JsonProperty annotations ensure JSON keys match original field names
Optional<T> is useful for fields that may be null in your API responses

Frequently Asked Questions

What are Jackson annotations?

Jackson is the most popular JSON library for Java. @JsonProperty annotation maps JSON keys to Java fields, allowing different naming conventions (e.g., JSON "user_name" to Java "userName"). When enabled, the generated classes work seamlessly with ObjectMapper for JSON parsing.

How are JSON types mapped to Java?

JSON strings → String, integers → Integer, floats → Double, booleans → Boolean, null → String (or Optional<String>), arrays → List<T>, objects → separate nested POJO classes. ISO-8601 dates can be detected as Instant or LocalDate.

How are nested objects handled?

Nested JSON objects are converted to separate Java POJO classes. They are ordered children-first, so nested classes appear before the parent class that references them, ensuring valid Java code.

Should I use Optional?

Optional<T> is useful for representing nullable fields in a more type-safe way. However, note that Jackson requires additional configuration to serialize/deserialize Optional fields. If you are using Spring Boot, it works out of the box.

Is my data sent to a server?

No, all processing happens entirely in your browser. Your JSON data never leaves your device.

JSON to Java POJO Generator