Generate Java POJO classes from JSON data with Jackson/Gson annotations and builder pattern support.
Paste a representative JSON object and JSON to Java Class drafts Java POJO declarations from the structure it observes. Object keys become candidate Java members, while value shapes guide field types, array element types, and nested class definitions. Generation options can add Jackson or Gson mapping annotations and builder pattern support. The common surprise is that the result describes the pasted sample, not every valid payload from the same endpoint. Missing fields, null-only values, or mixed array contents can leave choices that require manual review.
Each JSON object supplies candidate members. Strings, booleans, numbers, objects, and arrays provide evidence for Java declarations, but JSON itself does not prescribe Java primitive, wrapper, collection, or numeric classes. Nested objects introduce another object shape, and arrays introduce an element shape. Because inference starts from concrete values, a property seen only as null cannot establish a specific Java value type.
Selecting Jackson or Gson changes the mapping metadata emitted with the class so the source targets the chosen serializer's annotation vocabulary. Builder pattern support changes the construction surface of the generated source. Neither option validates external payloads or creates a formal schema. The result is Java source to inspect, place in the appropriate package, and compile with the dependencies required by annotations you keep.
No. A JSON instance shows which properties occurred in that instance, but it does not declare required properties or presence rules. The generated class is therefore a structural draft, not a validation contract. Use endpoint documentation or a JSON Schema when requiredness matters, and decide separately whether nullable values should use wrappers, optionals, defaults, or validation annotations.
Choose the annotation family used by the code that will serialize or deserialize the class. Jackson annotations are appropriate for Jackson-based mapping, while Gson annotations are appropriate for Gson-based mapping. Selecting both is usually unnecessary. If the project relies only on Java member names that already match the JSON keys, annotations may not be needed, but removing them can change mappings for renamed properties.
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