[JAVA 실습 #3] http통신, REST API 호출, json 데이터 처리

[JAVA 실습 #3] http통신, REST API호출, json 데이터 처리 후 출력

 

<< 개발환경 >>

Windows

JDK1.8

Eclipse

 

<< 실습과정 >>

1. url: dummy.restapiexample.com/api/v1/employees

2. 연결 확인 및 연결에 걸린 시간 확인

3. response status code 확인

4. JSON 데이터 처리 및 출력 (org.json.simple 활용)

 

    # url 응답오류 발생시 json 파일로 저장 후 데이터 처리하는 경우 추가

    # org.json.simple 활용

 

json-simple-1.1.1.jar

0.02MB

 

 

라이브러리 classpath에 추가

이클립스 기준 > 프로젝트 폴더 우클릭 > Properties > Java Build Path > Libraries Tab > Add External JARs... > 추가

[이클립스(Eclipse)] 외부 라이브러리(jar) 추가

[이클립스(Eclipse)] 외부 라이브러리(jar) 추가

 

 

 

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.file.Paths;
 
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;
 
public class JsonParseTest {
 
    // get elapsed time of Connection
    private static HttpURLConnection testHttpUrlConnection() throws MalformedURLException, IOException {
        long startTime = System.currentTimeMillis();
        URL url = new URL("http://dummy.restapiexample.com/api/v1/employees");
        HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
        long endTime = System.currentTimeMillis();
        
        int statusCode = httpConn.getResponseCode();        
        String pf = (statusCode == 200) ? "success" : "fail";
        
        System.out.println("1. connection " + pf + " in " + (endTime - startTime) + " millisecond");
        System.out.println("2. Response code: " + statusCode);
        
        return httpConn;
    }
 
    // get response code from HttpUrlConnection
    private static int getResponseStatus() throws MalformedURLException, IOException {
        
        URL url = new URL("http://dummy.restapiexample.com/api/v1/employees");
        HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();        
        int responseCode = httpConn.getResponseCode();
        
        return responseCode;
    }
 
    // handle JSON data and get JSON string
    private static String getJsonObjectString(BufferedReader br)
            throws MalformedURLException, IOException, ParseException {
 
        JSONParser jsonPar = new JSONParser();
        JSONObject jsonObj = (JSONObject) jsonPar.parse(br);
 
        JSONObject outputJsonObj = new JSONObject();
        outputJsonObj.put("status", jsonObj.get("status").toString());
        outputJsonObj.put("data", ((JSONArray) jsonObj.get("data")).get(0));
        outputJsonObj.put("message", jsonObj.get("message"));
 
        String outputString = outputJsonObj.toJSONString();
        
        return outputString;
    }
    
    // get JSON string from json file
    private static String getJsonObjectStringFromFile() throws MalformedURLException, IOException, ParseException {
        System.out.println("\nRead from json file instead!!");
        String currentPath = Paths.get(".").normalize().toString();            
        FileReader fr = new FileReader(currentPath + ".\\employees.json");
        BufferedReader br = new BufferedReader(fr);
        
        String outputString = getJsonObjectString(br);
        
        return outputString;
    }
 
    // main method
    public static void main(String[] args) throws MalformedURLException, IOException, ParseException {
        
        HttpURLConnection httpConn = testHttpUrlConnection();        
        int statusCode = getResponseStatus();
        
        String res = null;
        if (statusCode == 200) {
            BufferedReader br = new BufferedReader(new InputStreamReader(httpConn.getInputStream()));            
            res = getJsonObjectString(br);
        } else {
            res = getJsonObjectStringFromFile();
        }        
        System.out.println("result string: " + res);
        
    }
 
}

 

응답 성공할 경우

 

응답 없는 경우 json파일 읽기