如何利用Google OAuth2 for Java lib 拿到access token，并用其访问我的网络资源

各位好，

我是一个JAVA新人，最近需要用google 的OAuth2 的java 库做一些事情，不知道如何下手，请指教。

程序要求如下：
用java程序实现一个安全认证，利用google OAuth2 拿到access token并访问受保护资源。

我在网上找到一些资源，写了如下代码。说实话，我不是特别理解这段代码。

首先跳转url如何定？我是打算在web server端实现这段code的，调试时是http:\\localhost，访问的受保护资源是https:\\staging.xxxx.com\v2\application。
其次，如何构造手访问资源的request？网上有一些访问google app的例子，但是不太明白，不知道怎么用。适合我这种要求吗。可否贡献一个这样的例子。

谢谢

	



	private static final Collection<String> SCOPE = Arrays.asList("https://www.googleapis.com/auth/urlshortener");  

	private static final String CALLBACK_URL = "urn:ietf:wg:oauth:2.0:oob";  

	private static final HttpTransport TRANSPORT = new NetHttpTransport();  

	private static final JsonFactory JSON_FACTORY = new JacksonFactory();

		

	private static final String CLIENT_ID = "xxxxx"; //use your client ID

	private static final String CLIENT_SECRET = "xxxxx";  //use your client secret  



                GoogleAuthorizationCodeFlow authorizationCodeFlow = new GoogleAuthorizationCodeFlow

                .Builder(TRANSPORT, JSON_FACTORY, CLIENT_ID, CLIENT_SECRET, SCOPE)

                .setCredentialDataStore(new MemoryDataStoreFactory().getDataStore("tokens"))

                .build();

		

		String userId = "user-id";

		Credential credential = authorizationCodeFlow.loadCredential(userId);

		if (credential == null) {

		    GoogleAuthorizationCodeRequestUrl authorizationUrl = authorizationCodeFlow.newAuthorizationUrl();

		    authorizationUrl.setRedirectUri(GoogleOAuthConstants.OOB_REDIRECT_URI);

		    //LOGGER.error("Please, authorize application. Visit {}", authorizationUrl);

		    Scanner s = new Scanner(System.in);

		    String code = s.nextLine();

		    GoogleAuthorizationCodeTokenRequest tokenRequest = authorizationCodeFlow.newTokenRequest(code);

		    tokenRequest.setRedirectUri(GoogleOAuthConstants.OOB_REDIRECT_URI);

		    GoogleTokenResponse tokenResponse = tokenRequest.execute();

		    credential = authorizationCodeFlow.createAndStoreCredential(tokenResponse, userId);