vitaminac/EmailTemplate.html

## EmailTemplate.html
<!DOCTYPE html>
<html>
<head>
</head>
<body>

<button id="openGrantPage" type="button">Click Me!</button>

<script>
    document.getElementById("openGrantPage").onclick = function () {
        var OAuthUrl = "https://accounts.google.com/o/oauth2/v2/auth?";
        var scope = "https://mail.google.com/+https://www.googleapis.com/auth/userinfo.email";
        var client_id = "???";
        var response_type = "code";
        var redirect_uri = window.location.protocol + "//" + window.location.host + "/Gmail/oauth/";
        var url = OAuthUrl + "scope=" + scope + "&client_id=" + client_id + "&redirect_uri=" + redirect_uri + "&response_type=" + response_type;
        var w = window.open(url, "Gmail", "width=800, height=600");
        var timer = setInterval(function () {
            try {
                if (w.document.URL.indexOf(redirect_uri) != -1) {
                    debugger;
                    clearInterval(timer);
                    w.close();
                    var code = w.document.URL.replace(redirect_uri + "?code=", "");
                    console.log(code);
                }
            } catch (e) {
                console.log(e);
            }
        }, 100);
    }
</script>
</body>
</html>

## GmailOAuth.java
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.InetSocketAddress;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.LinkedHashMap;
import java.util.Map;

public class GmailOAuth {

    private static final String ClientId = "????";
    private static final String Secret = "???";
    private static final String Redirect_URI = "http://127.0.0.1:59917/Gmail/oauth/";
    private static final String Google_User_Info_API = "https://www.googleapis.com/oauth2/v2/userinfo";

    public static void main(String[] args) {
        try {
//            startServer();
            String refreshToken = fetchRefreshToken("???");
            System.out.println(refreshToken);
            String accessToken = fetchAccessToken(refreshToken);
            System.out.println(accessToken);
            String email = fetchEmailAddress(accessToken);
            System.out.println(email);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static String fetchToken(Map<String, Object> params, String tokenName, String tokenURL) throws Exception {
        StringBuilder postData = new StringBuilder();
        for (Map.Entry<String, Object> param : params.entrySet()) {
            if (postData.length() != 0) {
                postData.append('&');
            }
            postData.append(param.getKey());
            postData.append('=');
            postData.append(param.getValue());
        }
        byte[] postDataBytes = postData.toString().getBytes("UTF-8");
        URL url = new URL(tokenURL);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setDoOutput(true);
        con.setUseCaches(false);
        con.setRequestMethod("POST");
        con.getOutputStream().write(postDataBytes);
        BufferedReader reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
        StringBuffer buffer = new StringBuffer();
        for (String line = reader.readLine(); line != null; line = reader.readLine()) {
            buffer.append(line);
        }
        JSONObject json = new JSONObject(buffer.toString());
        return json.getString(tokenName);
    }

    private static String fetchRefreshToken(String authorizationCode) throws Exception {
        Map<String, Object> params = new LinkedHashMap<>();
        params.put("code", authorizationCode);
        params.put("client_id", ClientId);
        params.put("client_secret", Secret);
        params.put("redirect_uri", Redirect_URI);
        params.put("grant_type", "authorization_code");
        return fetchToken(params, "refresh_token", "https://www.googleapis.com/oauth2/v4/token");
    }

    private static String fetchAccessToken(String refreshToken) throws Exception {
        Map<String, Object> params = new LinkedHashMap<>();
        params.put("grant_type", "refresh_token");
        params.put("client_id", ClientId);
        params.put("client_secret", Secret);
        params.put("refresh_token", refreshToken);
        return fetchToken(params, "access_token", "https://www.googleapis.com/oauth2/v4/token");
    }

    private static String fetchEmailAddress(String accessToken) throws Exception {
        URL url = new URL(Google_User_Info_API);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setUseCaches(false);
        con.setRequestMethod("GET");
        con.setRequestProperty("Authorization", "Bearer " + accessToken);
        con.setDoOutput(true);
        BufferedReader reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
        StringBuffer buffer = new StringBuffer();
        for (String line = reader.readLine(); line != null; line = reader.readLine()) {
            buffer.append(line);
        }
        JSONObject json = new JSONObject(buffer.toString());
        return json.getString("email");
    }

    private static void startServer() throws Exception {
        HttpServer server = HttpServer.create(new InetSocketAddress(0), 0);
        server.createContext("/", new HttpHandler() {
            @Override
            public void handle(HttpExchange httpExchange) throws IOException {
                Path path = FileSystems.getDefault().getPath("src/test/java/", "EmailTemplate.html");
                String response = new String(Files.readAllBytes(path), StandardCharsets.UTF_8);
                httpExchange.sendResponseHeaders(200, response.length());
                OutputStream os = httpExchange.getResponseBody();
                os.write(response.getBytes());
                os.close();
            }
        });
        server.start();
        System.out.println("http://127.0.0.1:" + server.getAddress().getPort());
    }
}
	<!DOCTYPE html>
	<html>
	<head>
	</head>
	<body>

	<button id="openGrantPage" type="button">Click Me!</button>

	<script>
	document.getElementById("openGrantPage").onclick = function () {
	var OAuthUrl = "https://accounts.google.com/o/oauth2/v2/auth?";
	var scope = "https://mail.google.com/+https://www.googleapis.com/auth/userinfo.email";
	var client_id = "???";
	var response_type = "code";
	var redirect_uri = window.location.protocol + "//" + window.location.host + "/Gmail/oauth/";
	var url = OAuthUrl + "scope=" + scope + "&client_id=" + client_id + "&redirect_uri=" + redirect_uri + "&response_type=" + response_type;
	var w = window.open(url, "Gmail", "width=800, height=600");
	var timer = setInterval(function () {
	try {
	if (w.document.URL.indexOf(redirect_uri) != -1) {
	debugger;
	clearInterval(timer);
	w.close();
	var code = w.document.URL.replace(redirect_uri + "?code=", "");
	console.log(code);
	}
	} catch (e) {
	console.log(e);
	}
	}, 100);
	}
	</script>
	</body>
	</html>
	import com.sun.net.httpserver.HttpExchange;
	import com.sun.net.httpserver.HttpHandler;
	import com.sun.net.httpserver.HttpServer;
	import org.json.JSONObject;

	import java.io.BufferedReader;
	import java.io.IOException;
	import java.io.InputStreamReader;
	import java.io.OutputStream;
	import java.net.HttpURLConnection;
	import java.net.InetSocketAddress;
	import java.net.URL;
	import java.nio.charset.StandardCharsets;
	import java.nio.file.FileSystems;
	import java.nio.file.Files;
	import java.nio.file.Path;
	import java.util.LinkedHashMap;
	import java.util.Map;

	public class GmailOAuth {

	private static final String ClientId = "????";
	private static final String Secret = "???";
	private static final String Redirect_URI = "http://127.0.0.1:59917/Gmail/oauth/";
	private static final String Google_User_Info_API = "https://www.googleapis.com/oauth2/v2/userinfo";

	public static void main(String[] args) {
	try {
	// startServer();
	String refreshToken = fetchRefreshToken("???");
	System.out.println(refreshToken);
	String accessToken = fetchAccessToken(refreshToken);
	System.out.println(accessToken);
	String email = fetchEmailAddress(accessToken);
	System.out.println(email);
	} catch (Exception e) {
	e.printStackTrace();
	}
	}

	private static String fetchToken(Map<String, Object> params, String tokenName, String tokenURL) throws Exception {
	StringBuilder postData = new StringBuilder();
	for (Map.Entry<String, Object> param : params.entrySet()) {
	if (postData.length() != 0) {
	postData.append('&');
	}
	postData.append(param.getKey());
	postData.append('=');
	postData.append(param.getValue());
	}
	byte[] postDataBytes = postData.toString().getBytes("UTF-8");
	URL url = new URL(tokenURL);
	HttpURLConnection con = (HttpURLConnection) url.openConnection();
	con.setDoOutput(true);
	con.setUseCaches(false);
	con.setRequestMethod("POST");
	con.getOutputStream().write(postDataBytes);
	BufferedReader reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
	StringBuffer buffer = new StringBuffer();
	for (String line = reader.readLine(); line != null; line = reader.readLine()) {
	buffer.append(line);
	}
	JSONObject json = new JSONObject(buffer.toString());
	return json.getString(tokenName);
	}

	private static String fetchRefreshToken(String authorizationCode) throws Exception {
	Map<String, Object> params = new LinkedHashMap<>();
	params.put("code", authorizationCode);
	params.put("client_id", ClientId);
	params.put("client_secret", Secret);
	params.put("redirect_uri", Redirect_URI);
	params.put("grant_type", "authorization_code");
	return fetchToken(params, "refresh_token", "https://www.googleapis.com/oauth2/v4/token");
	}

	private static String fetchAccessToken(String refreshToken) throws Exception {
	Map<String, Object> params = new LinkedHashMap<>();
	params.put("grant_type", "refresh_token");
	params.put("client_id", ClientId);
	params.put("client_secret", Secret);
	params.put("refresh_token", refreshToken);
	return fetchToken(params, "access_token", "https://www.googleapis.com/oauth2/v4/token");
	}

	private static String fetchEmailAddress(String accessToken) throws Exception {
	URL url = new URL(Google_User_Info_API);
	HttpURLConnection con = (HttpURLConnection) url.openConnection();
	con.setUseCaches(false);
	con.setRequestMethod("GET");
	con.setRequestProperty("Authorization", "Bearer " + accessToken);
	con.setDoOutput(true);
	BufferedReader reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
	StringBuffer buffer = new StringBuffer();
	for (String line = reader.readLine(); line != null; line = reader.readLine()) {
	buffer.append(line);
	}
	JSONObject json = new JSONObject(buffer.toString());
	return json.getString("email");
	}

	private static void startServer() throws Exception {
	HttpServer server = HttpServer.create(new InetSocketAddress(0), 0);
	server.createContext("/", new HttpHandler() {
	@Override
	public void handle(HttpExchange httpExchange) throws IOException {
	Path path = FileSystems.getDefault().getPath("src/test/java/", "EmailTemplate.html");
	String response = new String(Files.readAllBytes(path), StandardCharsets.UTF_8);
	httpExchange.sendResponseHeaders(200, response.length());
	OutputStream os = httpExchange.getResponseBody();
	os.write(response.getBytes());
	os.close();
	}
	});
	server.start();
	System.out.println("http://127.0.0.1:" + server.getAddress().getPort());
	}
	}