Java EE 8 comes with a JAXB-like, declarative JSON binding called JSON-B (JSR-367). JSON-B is consistent with JAXB and other Java EE/SE APIs. Jakarta EE takes Java EE 8 JSON (P and B) to the next level. Its API is exposed via the javax.json.bind.Jsonb and javax.json.bind.JsonbBuilder classes:

Jsonb jsonb = JsonbBuilder.create();

For deserialization, we use Jsonb.fromJson(), while, for serialization, we use Jsonb.toJson():

• Let's read melons_array.json as an Array of Melon:

Melon[] melonsArray = jsonb.fromJson(Files.newBufferedReader(
  pathArray, StandardCharsets.UTF_8), Melon[].class);

• Let's read melons_array.json as a List of Melon:

List<Melon> melonsList 
  = jsonb.fromJson(Files.newBufferedReader(
    pathArray, StandardCharsets.UTF_8), ArrayList.class);

• Let's read melons_map.json as a Map of Melon:

Map<String, Melon> melonsMap 
  = jsonb.fromJson(Files.newBufferedReader(
    pathMap, StandardCharsets.UTF_8), HashMap.class);

• Let's read melons_raw.json line by line into a Map:

Map<String, String> stringMap = new HashMap<>();

try (BufferedReader br = Files.newBufferedReader(
    pathRaw, StandardCharsets.UTF_8)) {

  String line;

  while ((line = br.readLine()) != null) {
    stringMap = jsonb.fromJson(line, HashMap.class);
    System.out.println("Current map is: " + stringMap);
  }
}

• Let's read melons_raw.json line by line into a Melon:

try (BufferedReader br = Files.newBufferedReader(
    pathRaw, StandardCharsets.UTF_8)) {

  String line;

  while ((line = br.readLine()) != null) {
    Melon melon = jsonb.fromJson(line, Melon.class);
    System.out.println("Current melon is: " + melon);
  }
}

• Let's write an object into a JSON file (melons_output.json):

Path path = Paths.get("melons_output.json");

jsonb.toJson(melonsMap, Files.newBufferedWriter(path,
  StandardCharsets.UTF_8, StandardOpenOption.CREATE, 
    StandardOpenOption.WRITE));