[JAVA 실습 #7] json data 객체(Object)에 매핑(Mapping) (2) - json simple

자바(JAVA) 실습 - json data 객체(Object)에 매핑(Mapping) (2) - json simple

 

환경 OpenJDK 1.8

 

1. json 파일 문자열(String)로 읽기

2. 문자열을 객체로 매핑

 

 

 

[ TestSimpleJson.java ]

package test.json;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
 
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;
 
import test.model.Product;
 
public class TestSimpleJson {
 
    private static final String FILELOCATION = "test/init.json";
 
    public static void main(String[] args) {
        Long start = System.nanoTime();
        String result = readJsonFile();
//        System.out.println("result: " + result);
 
        List<Product> productList = getProductList(result);
        Long end = System.nanoTime();
        Long elapsedTime = end - start;
        
        System.out.println("productList: " + productList.toString());
        System.out.println("Elapsed Time: " + elapsedTime + " nano sec.");
    }
 
    private static String readJsonFile() {
 
        ClassLoader classLoader = TestSimpleJson.class.getClassLoader();
        StringBuilder sb = new StringBuilder();
        try (InputStream inputStream = classLoader.getResourceAsStream(FILELOCATION);
                BufferedReader br = new BufferedReader(new InputStreamReader(inputStream))) {
            String line = "";
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
            throw new RuntimeException();
        }
 
        return sb.toString();
    }
 
    private static Map getMapFromString(String jsonString) {
        JSONParser jsonParser = new JSONParser();
        Map map = null;
        try {
            Object object = jsonParser.parse(jsonString);
            map = (Map) object;
            if (map.isEmpty()) {
                throw new RuntimeException();
            }
        } catch (ParseException e) {
            e.printStackTrace();
            throw new RuntimeException();
        }
        return map;
    }
 
    private static List<Product> getProductList(String jsonString) {
 
        Map map = getMapFromString(jsonString);
 
        JSONArray jsonArray = (JSONArray) map.get("product");
        List<Product> productList = new ArrayList<>();
        for (int i = 0; i < jsonArray.size(); i++) {
            JSONObject prodObject = (JSONObject) jsonArray.get(i);
            Product product = new Product(prodObject.get("productName").toString(),
                                     prodObject.get("productDescription").toString(),
                                     new BigDecimal(prodObject.get("productPrice").toString()));
            productList.add(product);
        }
 
        return productList;
    }
 
}