JSON to Java POJO Generator — Convert JSON to Java Classes Online Free

Generate Java POJO classes from JSON

Root class

Style

JSON lib

@JsonProperty / @SerializedName @Nullable (JSR-305)

JSON Input

Java Output

Code Style Reference

Lombok @Data — Adds @Data which auto-generates getters, setters, equals, hashCode, and toString at compile time. Requires the Lombok dependency. The cleanest option for Spring Boot projects.
Getter + Setter — Plain POJO with explicit getXxx() and setXxx() methods. No extra dependencies. Verbose but universally compatible.
Java Record — Immutable value class using the record keyword (Java 16+). Auto-generates a canonical constructor, accessors, equals, hashCode, and toString. Ideal for DTOs and read-only response models.

Annotation Libraries

Jackson — The default JSON library in Spring Boot. @JsonProperty("field_name") maps a snake_case JSON key to a camelCase Java field. @JsonIgnoreProperties(ignoreUnknown = true) on the class prevents errors when the API adds new fields.
Gson — Google's JSON library. Uses @SerializedName("field_name") for field mapping. Common in Android and non-Spring Java projects.

Frequently Asked Questions

How are JSON types mapped to Java types?

string → String, number (integer) → Integer, number (decimal) → Double, boolean → Boolean, null → Object, array → List<T>, object → nested class. Wrapper types (Integer vs int) are used throughout so fields can represent null values from JSON.

When should I use Java Records vs Lombok?

Use Records for immutable DTOs — API response models you only read, never mutate. Use Lombok @Data for entities and models that need setters (e.g., JPA entities, request bodies that frameworks populate by reflection). Records require Java 16+; Lombok works from Java 8.

How do I handle snake_case JSON keys in Spring Boot?

Either add @JsonProperty("snake_key") per field (generated by this tool when enabled), or configure Jackson globally: spring.jackson.property-naming-strategy=SNAKE_CASE in application.properties. The global approach is cleaner when all your API keys follow snake_case consistently.