[JAVA 실습 #7] json data 객체(Object)에 매핑(Mapping) (3) - Gson

자바(JAVA) 실습 - json data 객체(Object)에 매핑(Mapping) (3) - Gson

 

환경 OpenJDK 1.8

 

1. json 파일 문자열(String)로 읽기

2. 문자열을 객체로 매핑

 

 

 

[ TestGson.java ]

package test.gson;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
 
import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
 
import test.model.Product;
 
public class TestGson {
 
    private static final String FILELOCATION = "test/init.json";
 
    public static void main(String[] args) {
        Long start = System.nanoTime();
        String result = readJsonFile(FILELOCATION);
//        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(String file) {
        ClassLoader classLoader = TestGson.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();
        }
        
        return sb.toString();
    }
    
    private static List<Product> getProductList(String jsonString) {
        JsonObject jsonObject = new Gson().fromJson(jsonString, JsonObject.class);
        JsonElement productElement = jsonObject.get("product");
        JsonArray prodElementAsJsonArray = productElement.getAsJsonArray();
        
        List<Product> productList = new ArrayList<>();
        for (JsonElement prodElement : prodElementAsJsonArray) {
            JsonObject prodObject = prodElement.getAsJsonObject();
            
            Product product = new Product();
            product.setProductName(prodObject.get("productName").toString());
            product.setProductDescription(prodObject.get("productDescription").toString());
            product.setProductPrice(prodObject.get("productPrice").getAsBigDecimal());
            productList.add(product);
        }
        
        return productList;
    }
 
}