Jackson is a popular and fast library dedicated to processing (serializing/deserializing) JSON data. The Jackson API relies on  com.fasterxml.jackson.databind.ObjectMapper. Let's go over the preceding examples again, but this time using Jackson:

ObjectMapper mapper = new ObjectMapper();

For deserialization, we use ObjectMapper.readValue(), while for serialization, we use ObjectMapper.writeValue():

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

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

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

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

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

Map<String, Melon> melonsMap 
  = mapper.readValue(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 = mapper.readValue(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 = mapper.readValue(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");

mapper.writeValue(Files.newBufferedWriter(path, 
  StandardCharsets.UTF_8, StandardOpenOption.CREATE, 
    StandardOpenOption.WRITE), melonsMap);