JSON Formatter, Minifier, and Validator in Java — DevToolsForYou

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JSON parsing and serialisation is built into every major language. Here is how to parse a JSON string, format (pretty-print) JSON, and handle common edge cases in each language.

Java has no built-in JSON library. Jackson (ObjectMapper) is the standard choice; Gson is also popular.

Also in:JavaScript / Node.js Python Go PHP Ruby Rust C# / .NET

Jackson (most common)

// Maven: com.fasterxml.jackson.core:jackson-databind
import com.fasterxml.jackson.databind.*;

public class JsonExample {
    record User(String name, int age) {}

    public static void main(String[] args) throws Exception {
        ObjectMapper mapper = new ObjectMapper();

        // Parse JSON → object
        String json = "{"name":"Alice","age":30}";
        User user = mapper.readValue(json, User.class);
        System.out.println(user.name()); // Alice

        // Serialize object → JSON
        String out = mapper.writeValueAsString(user);
        System.out.println(out); // {"name":"Alice","age":30}

        // Pretty-print
        String pretty = mapper.writerWithDefaultPrettyPrinter()
                              .writeValueAsString(user);
        System.out.println(pretty);

        // Parse into Map (unknown structure)
        Map<String, Object> map = mapper.readValue(json, Map.class);
        System.out.println(map.get("name")); // Alice
    }
}

Notes & gotchas

ObjectMapper is thread-safe and expensive to create — make it a singleton or Spring bean.
Use @JsonProperty on fields to map different JSON key names to Java field names.
Enable mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false) to ignore extra JSON fields.

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JSON Formatter, Minifier, and Validator in other languages

JSON Formatter, Minifier, and Validator in JavaScript / Node.js

JavaScript has JSON.parse() and JSON.stringify() built in. Use the space parameter of JSON.stringify() for pretty-printing.

JSON Formatter, Minifier, and Validator in Python

Python's json module has json.loads() for parsing and json.dumps() for serialization. Use indent for pretty-printing.

JSON Formatter, Minifier, and Validator in Go

Go's encoding/json package uses struct tags for mapping. json.Marshal() serializes and json.Unmarshal() parses.

JSON Formatter, Minifier, and Validator in PHP

PHP has built-in json_encode() and json_decode() functions. Pass JSON_PRETTY_PRINT for formatted output.

JSON Formatter, Minifier, and Validator in Ruby

Ruby's standard library includes the json gem. Use JSON.parse to decode and JSON.generate (or JSON.pretty_generate) to encode.

JSON Formatter, Minifier, and Validator in Rust

Rust uses serde_json for JSON serialization and deserialization. Define structs with #[derive(Serialize, Deserialize)] for typed parsing.

JSON Formatter, Minifier, and Validator in C# / .NET

C# uses System.Text.Json (built-in since .NET 3.0) for JSON serialization. Use JsonSerializer.Serialize / Deserialize for typed objects.

JSON Formatter, Minifier, and Validator in Java — Code Examples