1. 문자열 입력받기
2. 메이븐 추가 + jackson 추가 (IntelliJ)
3. HTTP 요청 (HttpURLConnection)

Java Swing을 이용해 문자열을 입력 받고 해당 문자열을 HTTP 요청 보내는 과정을 설명하겠습니다.

1. 문자열 입력받기

300 * 150 크기의 프레임을 만들고 JTextField, JButton을 추가했습니다.

버튼을 클릭하면 입력한 내용이 출력되도록 작성하였습니다.

JTextField에 "test"를 입력했습니다.

전송 버튼을 누르면 정삭적으로 출력이 됩니다.

코드

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;


public class SwingHttpRequest extends JFrame {

    JTextField textField = new JTextField(20);
    JButton button = new JButton("전송");

    public static void main(String[] args) {
        SwingHttpRequest swingHttpRequest = new SwingHttpRequest();

        swingHttpRequest.sendText();
    }

    public void sendText() {
        add(textField);
        add(button);

        setVisible(true);
        setLayout(new FlowLayout());
        setSize(300, 150);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


        button.addActionListener(new ActionListener() { // 익명 객체
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println(textField.getText());
            }
        });
    }
}

2. 메이븐 추가 + jackson 추가 (IntelliJ)

JSON 요청을 보내기 위해 필요한 Jackson 의존성을 추가하기 위해 메이븐을 추가해줬습니다.

(1) Add Framework Support... > Maven 을 추가해줍니다.

(2) 생성된 pom.xml 파일에 아래 코드를 추가해줍니다.

<dependencies>
	<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
    <dependency>
    	<groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.13.2</version>
    </dependency>
</dependencies>

적용 후 pom.xml 이미지

3. HTTP 요청 (HttpURLConnection)

HttpURLConnection를 통해 HTTP 요청을 보냈습니다.

요청 보내기

서버 출력 (Spring Boot)

* 한글 & 특수문자 & 공백 전송은 안됩니다. 추가 처리가 필요합니다.

GET 요청

HttpURLConnection connection = null;

.
. 중략
.

	// GET
    public String sendHttpGetRequest(String targetURL, String jsonValues) throws IOException {
        //Create connection
        URL url = new URL(targetURL + jsonToQueryString(jsonValues));

        // Send request
        URLConnection connection = null;

        connection = url.openConnection();

        connection.setRequestProperty("Accept-Charset", "URF-8");

        // Get response
        InputStream response = connection.getInputStream();

        try (Scanner scanner = new Scanner(response)) {
            String responseBody = scanner.useDelimiter("\\A").next();
            return responseBody;
        }
    }

    // json(String) => queryString
    public String jsonToQueryString(String jsonValues) throws JsonProcessingException {
        String queryString  = "";

        HashMap<String,Object> jsonMap = null;

        jsonMap = new ObjectMapper().readValue(jsonValues, HashMap.class);

        for(String strKey : jsonMap.keySet()) {
            queryString += "?" + strKey + "=" + jsonMap.get(strKey);
        }

        return queryString;
    }

POST 요청

HttpURLConnection connection = null;

.
. 중략
.

	// POST
    public String sendHttpPostRequest(String targetURL, String jsonValues) {
        try {
            // Create connection
            URL url = new URL(targetURL);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");

            connection.setRequestProperty("Content-Type", "application/json; utf-8");
            connection.setRequestProperty("Content-Length", Integer.toString(jsonValues.getBytes().length));
            connection.setRequestProperty("Content-Language", "en-US");

            connection.setUseCaches(false);
            connection.setDoOutput(true);

            // Send request
            DataOutputStream wr = new DataOutputStream (connection.getOutputStream());
            wr.writeBytes(jsonValues);
            wr.flush();
            wr.close();

            // Get Response
            InputStream is = connection.getInputStream();
            BufferedReader rd = new BufferedReader(new InputStreamReader(is));
            StringBuilder response = new StringBuilder(); // or StringBuffer if Java version 5+
            String line;
            while ((line = rd.readLine()) != null) {
                response.append(line);
                response.append('\r');
            }
            rd.close();
            return response.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
    }

전체 코드

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class SwingHttpRequest extends JFrame {

    static HttpURLConnection connection = null;

    public static void main(String[] args) throws IOException {
        SwingHttpRequest swingHttpRequest = new SwingHttpRequest();

        swingHttpRequest.sendText(swingHttpRequest);
    }

    public void sendText(SwingHttpRequest swingHttpRequest) {
        JTextField textField = new JTextField(20);
        JButton button = new JButton("GET, POST 요청");

        add(textField);
        add(button);

        setVisible(true);
        setLayout(new FlowLayout());
        setSize(300, 150);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        button.addActionListener(new ActionListener() { // 익명 객체
            @Override
            public void actionPerformed(ActionEvent e) {
                Map<String, String> mapValues = new HashMap<>();
                mapValues.put("value", textField.getText());
                try {
                    String jsonValues = new ObjectMapper().writeValueAsString(mapValues);

                    String getUrl = "http://localhost:8080/get";
                    String postUrl = "http://localhost:8080/post";

                    // GET 요청
                    String getResponse = swingHttpRequest.sendHttpGetRequest(getUrl, jsonValues);
                    System.out.println("getResponse : " + getResponse);

                    // POST 요청
                    String postResponse = swingHttpRequest.sendHttpPostRequest(postUrl, jsonValues);
                    System.out.println("postResponse : " + postResponse);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        });
    }

    // POST
    public String sendHttpPostRequest(String targetURL, String jsonValues) {
        try {
            // Create connection
            URL url = new URL(targetURL);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");

            connection.setRequestProperty("Content-Type", "application/json; utf-8");
            connection.setRequestProperty("Content-Length", Integer.toString(jsonValues.getBytes().length));
            connection.setRequestProperty("Content-Language", "en-US");

            connection.setUseCaches(false);
            connection.setDoOutput(true);

            // Send request
            DataOutputStream wr = new DataOutputStream (connection.getOutputStream());
            wr.writeBytes(jsonValues);
            wr.flush();
            wr.close();

            // Get Response
            InputStream is = connection.getInputStream();
            BufferedReader rd = new BufferedReader(new InputStreamReader(is));
            StringBuilder response = new StringBuilder(); // or StringBuffer if Java version 5+
            String line;
            while ((line = rd.readLine()) != null) {
                response.append(line);
                response.append('\r');
            }
            rd.close();
            return response.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
    }

    // GET
    public String sendHttpGetRequest(String targetURL, String jsonValues) throws IOException {
        //Create connection
        URL url = new URL(targetURL + jsonToQueryString(jsonValues));

        // Send request
        URLConnection connection = null;

        connection = url.openConnection();

        connection.setRequestProperty("Accept-Charset", "URF-8");

        // Get response
        InputStream response = connection.getInputStream();

        try (Scanner scanner = new Scanner(response)) {
            String responseBody = scanner.useDelimiter("\\A").next();
            return responseBody;
        }
    }

    // json(String) => queryString
    public String jsonToQueryString(String jsonValues) throws JsonProcessingException {
        String queryString  = "";

        HashMap<String,Object> jsonMap = null;

        jsonMap = new ObjectMapper().readValue(jsonValues, HashMap.class);

        for(String strKey : jsonMap.keySet()) {
            queryString += "?" + strKey + "=" + jsonMap.get(strKey);
        }

        return queryString;
    }
}

서버 코드 (TestController)

import com.testserver.ValueVo;
import org.springframework.web.bind.annotation.*;

@RestController
public class TestController {

    @GetMapping("/get")
    public String getTest(@RequestParam String value) {
        System.out.println("get : " + value);
        return value;
    }

    @PostMapping("/post")
    public String postTest(@RequestBody ValueVo valueVo) {
        String value = valueVo.getValue();
        System.out.println("post : " + value);
        return value;
    }

}

서버 코드 (ValueVO)

import lombok.Data;

@Data
public class ValueVo {
    private String value;
}

참고 링크

https://stackoverflow.com/questions/1359689/how-to-send-http-request-in-java

https://stackoverflow.com/questions/2793150/how-to-use-java-net-urlconnection-to-fire-and-handle-http-requests