objectmapper jackson file to object code example

Example 1: how to read file in java jacakson

try {
    // create object mapper instance
    ObjectMapper mapper = new ObjectMapper();

    // convert JSON file to map
    Map<?, ?> map = mapper.readValue(Paths.get("book.json").toFile(), Map.class);

    // print map entries
    for (Map.Entry<?, ?> entry : map.entrySet()) {
        System.out.println(entry.getKey() + "=" + entry.getValue());
    }

} catch (Exception ex) {
    ex.printStackTrace();
}

Example 2: java json deserializer

private Car parseCar(JsonNode node) {
        Car car;
        ObjectMapper mapper = new ObjectMapper();
        SimpleModule module = new SimpleModule().addDeserializer(Car.class, new CarDeserializer());
        mapper.registerModule(module);
        organization = mapper.convertValue(node, Car.class);
        return car;
}

//deserializer class
public class CarDeserializer extends StdDeserializer<Car> {

    public CarDeserializer() {
        super(Car.class);
    }

    @Override
    public Car deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.registerModule(new JodaModule());

        Car car = new Car();
        car.setName(getValueAsText(root, "carName"));
        car.setDoorCount(getValueAsInt(root,"doorCount"));
        car.setColor(getValueAsText(root,"color"));
		car.setType(getValueAsText(root,"type"));

        return car;
    }

}

Example 3: convert json to object jackson

ObjectMapper objectMapper = new ObjectMapper();

String carJson =
    "{ \"brand\" : \"Mercedes\", \"doors\" : 5 }";

try {
    Car car = objectMapper.readValue(carJson, Car.class);

    System.out.println("car brand = " + car.getBrand());
    System.out.println("car doors = " + car.getDoors());
} catch (IOException e) {
    e.printStackTrace();
}