Jackson中JsonNode使用示例

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test;

public class JsonTreeModelDemo {

    /**
     * 获取 JSON 字符串中的 JsonNode
     *
     * @throws JsonProcessingException
     */
    @Test
    public void test1() throws JsonProcessingException {
        String carJson = "{ \"brand\" : \"Mercedes\", \"doors\" : 5," +
                "  \"owners\" : [\"John\", \"Jack\", \"Jill\"]," +
                "  \"nestedObject\" : { \"field\" : \"value\" } }";
        ObjectMapper objectMapper = new ObjectMapper();
//        JsonNode jsonNode = objectMapper.readValue(carJson, JsonNode.class);
        JsonNode jsonNode = objectMapper.readTree(carJson);

        JsonNode brandNode = jsonNode.get("brand");
        String brand = brandNode.asText();
        System.out.println("brand = " + brand);

        JsonNode doorsNode = jsonNode.get("doors");
        int doors = doorsNode.asInt();
        System.out.println("doors = " + doors);

        JsonNode ownersNodeArray = jsonNode.get("owners");
        JsonNode owners = ownersNodeArray.get(0);
        String john = owners.asText();
        String s = ownersNodeArray.toString();
        System.out.println(s);
        System.out.println("john  = " + john);

        JsonNode child = jsonNode.get("nestedObject");
        JsonNode childField = child.get("field");
        String field = childField.asText();
        System.out.println("field = " + field);
    }

    /**
     * Java对象转JsonNode
     */
    @Test
    public void test2() {
        ObjectMapper objectMapper = new ObjectMapper();
        Car car = new Car();
        car.setBrand("Cadillac");
        car.setDoors(4);

        JsonNode carJsonNode = objectMapper.valueToTree(car);
        System.out.println(carJsonNode.toString());
    }

    /**
     * JsonNode转Java对象
     */
    @Test
    public void test3() throws JsonProcessingException {
        ObjectMapper objectMapper = new ObjectMapper();
        String carJson = "{ \"brand\" : \"Mercedes\", \"doors\" : 5 }";
        JsonNode carJsonNode = objectMapper.readTree(carJson);
        Car car = objectMapper.treeToValue(carJsonNode, Car.class);
        System.out.println(car);
    }

}