[JAVA 실습 #7] json data 객체(Object)에 매핑(Mapping) (4) - Jackson

자바(JAVA) 실습 - json data 객체(Object)에 매핑(Mapping) (4) - Jackson

 

환경 OpenJDK 1.8

 

1. json 파일 스트림(stream)으로 읽기

2. JsonNode로 매핑

3. 객체(Object)로 매핑

 

 

 

[ TestJackson.java ]

package test.fasterxml;
 
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
 
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
 
import test.model.Product;
 
public class TestJackson {
 
    private static final String FILELOCATION = "test/init.json";
 
    public static void main(String[] args) {
        Long start = System.nanoTime();
        InputStream is = getStreamFromFile();
        JsonNode productNode = getProductNode(is);
        List<Product> productList = getProductFromNode(productNode);
        Long end = System.nanoTime();
        Long elapsedTime = end - start;
        
        System.out.println("productList: " + productList.toString());
        System.out.println("Elapsed Time: " + elapsedTime + " nano sec.");
    }
 
    private static InputStream getStreamFromFile() {
        ClassLoader classLoader = TestJackson.class.getClassLoader();
        InputStream is = classLoader.getResourceAsStream(FILELOCATION);
        if (is == null) {
            throw new RuntimeException();
        }
        return is;
    }
 
    private static JsonNode getProductNode(InputStream is) {
        if (is == null) {
            throw new RuntimeException();
        }
 
        DataInputStream dis = new DataInputStream(is);
        ObjectMapper objectMapper = new ObjectMapper();
 
        try {
            JsonNode productNode = objectMapper.readTree(dis).findPath("product");
            return productNode;
        } catch (IOException e) {
            e.printStackTrace();
            throw new RuntimeException();
        }
    }
 
    private static List<Product> getProductFromNode(JsonNode productNode) {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        List<Product> productList = new ArrayList<>();
        productList = objectMapper.convertValue(productNode, new TypeReference<List<Product>>() {
        });
 
        return productList;
    }
 
}