Connect to mailbox using IMAP Oauth2

imap.java

public String getAccessTokenByClientCredentialGrant() {

		String accessToken = null;
		String clientId = imapClientId;
		String secret = imapSecret;
		String authority = "https://login.microsoftonline.com/" + imapTenantId + "/oauth2/v2.0/token";
		String scope = "https://outlook.office365.com/.default";
		log.info("Client ID : " + clientId);
		log.info("Client Secret : " + secret);
		log.info("Auth Server: " + authority);
		log.info("Scope: " + scope);

		try {

			ConfidentialClientApplication app = ConfidentialClientApplication
					.builder(clientId, ClientCredentialFactory.createFromSecret(secret)).authority(authority).build();

			// With client credentials flows the scope is ALWAYS of the shape
			// "resource/.default", as the
			// application permissions need to be set statically (in the portal), and then
			// granted by a tenant administrator
			ClientCredentialParameters clientCredentialParam = ClientCredentialParameters
					.builder(Collections.singleton(scope)).build();

			CompletableFuture<IAuthenticationResult> future = app.acquireToken(clientCredentialParam);
			IAuthenticationResult result = future.get();
			accessToken = result.accessToken();

		} catch (Exception e) {
			log.error("Exception in acquiring token: " + e.getMessage());
			e.printStackTrace();
		}
		log.info("Access Token : " + accessToken);
		return accessToken;
	}

	// This method connects to store using the access token
	public Store connectViaOauth(String userEmailId, String oauth2AccessToken) throws Exception {
		Store store = null;

		String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";
		Properties props = new Properties();

		props.put("mail.imaps.ssl.enable", "true");
		props.put("mail.imaps.sasl.enable", "true");
		props.put("mail.imaps.port", imapPort);

		props.put("mail.imaps.auth.mechanisms", "XOAUTH2");
		props.put("mail.imaps.sasl.mechanisms", "XOAUTH2");

		props.put("mail.imaps.auth.login.disable", "true");
		props.put("mail.imaps.auth.plain.disable", "true");

		props.setProperty("mail.imaps.socketFactory.class", SSL_FACTORY);
		props.setProperty("mail.imaps.socketFactory.fallback", "false");
		props.setProperty("mail.imaps.socketFactory.port", imapPort);
		props.setProperty("mail.imaps.starttls.enable", "true");

		props.put("mail.debug", "true");
		props.put("mail.debug.auth", "true");

		Session session = Session.getInstance(props);
		session.setDebug(true);

		store = session.getStore("imaps");

		log.info("OAUTH2 IMAP trying to connect with system properties to Host:" + imapHost + ", Port: " + imapPort
				+ ", userEmailId: " + userEmailId + ", AccessToken: " + oauth2AccessToken);
		try {

			store.connect(imapHost, userEmailId, oauth2AccessToken);
			log.info("IMAP connected with system properties to Host:" + imapHost + ", Port: " + imapPort
					+ ", userEmailId: " + userEmailId + ", AccessToken: " + oauth2AccessToken);
			if (store.isConnected()) {
				log.info("Connection Established using imap protocol successfully !");
			}
		} catch (Exception e) {
			log.error("Store.Connect failed with the errror: " + e.getMessage());
			StringWriter sw = new StringWriter();
			e.printStackTrace(new PrintWriter(sw));
			String exceptionAsString = sw.toString();
			log.error(exceptionAsString);

		}

		return store;

	}