Develop Reference

Issues using Retrofit2 to call GitHub REST API to update existing file

I'm attempting to use Retrofit to call the GitHub API to update the contents of an existing file, but am getting 404s in my responses. For this question, I'm interested in updating this file. Here is the main code I wrote to try and achieve this:
GitHubUpdateFileRequest
public class GitHubUpdateFileRequest {
public String message = "Some commit message";
public String content = "Hello World!!";
public String sha = "shaRetrievedFromSuccessfulGETOperation";
public final Committer committer = new Committer();
private class Committer {
Author author = new Author();
private class Author {
final String name = "blakewilliams1";
final String email = "blake#blakewilliams.org";
}
}
}
**GitHubUpdateFileResponse **
public class GitHubUpdateFileResponse {
public GitHubUpdateFileResponse() {}
}
GitHubClient
public interface GitHubClient {
// Docs: https://docs.github.com/en/rest/reference/repos#get-repository-content
// WORKS FINE
#GET("/repos/blakewilliams1/blakewilliams1.github.io/contents/qr_config.json")
Call<GitHubFile> getConfigFile();
// https://docs.github.com/en/rest/reference/repos#create-or-update-file-contents
// DOES NOT WORK
#PUT("/repos/blakewilliams1/blakewilliams1.github.io/contents/qr_config.json")
Call<GitHubUpdateFileResponse> updateConfigFile(#Body GitHubUpdateFileRequest request);
}
Main Logic
// Set up the Retrofit client and add an authorization interceptor
UserAuthInterceptor interceptor =
new UserAuthInterceptor("blake#blakewilliams.org", "myActualGitHubPassword");
OkHttpClient.Builder httpClient =
new OkHttpClient.Builder().addInterceptor(interceptor);
Retrofit.Builder builder =
new Retrofit.Builder()
.baseUrl("https://api.github.com/")
.addConverterFactory(GsonConverterFactory.create());
Retrofit retrofit = builder.client(httpClient.build()).build();
client = retrofit.create(GitHubClient.class);
// Now make the request and process the response
GitHubUpdateFileRequest request = new GitHubUpdateFileRequest();
client.updateConfigFile(request).enqueue(new Callback<GitHubUpdateFileResponse>() {
#Override
public void onResponse(Call<GitHubUpdateFileResponse> call, Response<GitHubUpdateFileResponse> response) {
int responseCode = response.code();
// More code on successful update
}
#Override
public void onFailure(Call<GitHubUpdateFileResponse> call, Throwable t) {
Log.e("MainActivity", "Unable to update file" + t.getLocalizedMessage());
}
});
What currently happens:
Currently, the success callback is triggered, but with a response code of 404 like so:
Response{protocol=http/1.1, code=404, message=Not Found, url=https://api.github.com/repos/blakewilliams1/blakewilliams1.github.io/contents/qr_config.json}
Has anyone else encountered this? I first thought it was a problem with including '/content/' in the URL but I do the same thing for reading the file contents request and it works fine (also uses same URL just a GET instead of PUT).

For anyone interested in doing this in the future, I figured out the solution.
I needed to revise the request object structure
Rather than using an authentication interceptor, I instead added an access token to the header. Here is where you can create access tokens for Github, you only need to grant it permissions to the 'repos' options for this use case to work.
This is what my updated request object looks like:
public class GitHubUpdateFileRequest {
public String message;
public String content;
public String sha;
public final Committer committer = new Committer();
public GitHubUpdateFileRequest(String unencodedContent, String message, String sha) {
this.message = message;
this.content = Base64.getEncoder().encodeToString(unencodedContent.getBytes());
this.sha = sha;
}
private static class Committer {
final String name = "yourGithubUsername";
final String email = "email#yourEmailAddressForTheUsername.com";
}
}
Then from my code, I would just say:
GitHubUpdateFileRequest updateRequest = new GitHubUpdateFileRequest("Hello World File Contents", "This is the title of the commit", shaOfExistingFile);
For using this reqest, I updated the Retrofit client implementation like so:
// https://docs.github.com/en/rest/reference/repos#create-or-update-file-contents
#Headers({"Content-Type: application/vnd.github.v3+json"})
#PUT("/repos/yourUserName/yourRepository/subfolder/path/to/specific/file/theFile.txt")
Call<GitHubUpdateFileResponse> updateConfigFile(
#Header("Authorization") String authorization, #Body GitHubUpdateFileRequest request);
And I call that interface like this:
githubClient.updateConfigFile("token yourGeneratedGithubToken", request);
And yes, you do need the prefix "token ". You could hardcode that header into the interface, but I pass it in so that I can store it in locations outside of my version control's reach for security reasons.

Getting Cognito Credentials on Android

I need to authenticate a user using AWS's Cognito in Android and get a token to use on my future requests. Some information is provided to me by the backend but I still haven't managed to use it in the appropriate way, and Cognito's documentation did not help me on this. I have this fixed info:
Pool Region: us-east-1
Pool ID: us-east-1:xxxxx-xxxxx-xxxxx-xxxx-xxxxxxxx
And after authenticating the user on the login endpoint I get this info:
{
"cognitoId": "us-east-1:yyyy-yyyy-yyyy-yyyy-yyyyyyy",
"cognitoToken": "hH1Q8bCLh9-pamP6DCrC0-KY4rNtZ115xDedE224CeEanex-CCWh4tWUtJjPc_tU3d6eJ_7Uk23ceTNhCFYT1qnAL_7kAH_lHod4a1GQo29FuTLQSqx4lOFv2Ev3RvYcCzjyLEAA1-EIKBtfSm_YN9y6DHBOzDJ8owLJTxB0JEWvsWfATjug4P8hxCI97RVB2cetrmq4JvZr__bCziUb-7AifPvy4VMW3xLjJ7uyDvogwcx5gJ1rF8Z38_z7kREB1R_CYPRVQuoHzag0j9RoOTNeAYFGO42qgCewTl3Lvm5PUbTIGhCIp6y1RVWAPLEdMWmQ3LVpqJcZKLQRhMmEzOGMyTUiXSwiaXNzIjoiaHR0cHM6Ly9jb2duaXRvLWlkZW50aXR5LmFtYXpvbmF3cy5jb20iLCJleHAiOjE1MTE2NDEzMDksImlhdCI6MTUxMTYyNjkwOX0.QFWGxh_"
}
The IDs were omitted and the token was altered in order to preserve the information. It is important to note that the Pool ID (constant in the app) and the cognitoId (returned by the backend) are different.
I have a static Credentials Provider initialized like this:
credentialsProvider = new CognitoCachingCredentialsProvider(
getApplicationContext(), /* get the context for the application */
IDENTITY_POOL_ID, /* Identity Pool ID */
Regions.US_EAST_1 /* Region for your identity pool--US_EAST_1 or EU_WEST_1*/
);
This is the task that does the work of trying to get the Cognito auth:
private static final class CognitoAuthTask extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... strings) {
String userId = strings[0];
String token = strings[1];
String sessionToken = null;
try {
Map<String, String> logins = new HashMap<String, String>();
logins.put(userId, token);
credentialsProvider.setLogins(logins);
AWSSessionCredentials credentials = credentialsProvider.getCredentials();
sessionToken = credentials.getSessionToken();
} catch (Exception e) {
if (BuildConfig.DEBUG) {
e.printStackTrace();
}
} finally {
return sessionToken;
}
}
#Override
protected void onPostExecute(String authToken) {
super.onPostExecute(authToken);
cognitoAuthToken = authToken;
if (BuildConfig.DEBUG) {
Log.d("Cognito Token", cognitoAuthToken == null ? "null" : cognitoAuthToken);
}
}
}
And this is where I call it when I have the information from my login endpoint (as I showed above):
public void authenticateCognito(String userId, String token) {
new CognitoAuthTask().execute(userId, token);
}
The problem is that this is not working, I get this error here:
Invalid login token. Can't pass in a Cognito token. (Service:
AmazonCognitoIdentity; Status Code: 400; Error Code:
NotAuthorizedException; Request ID: zzzzzz-zzzz-zzzz-zzzz-zzzzzzzzzz)
The error happens on the task, on this line of code here:
credentialsProvider.getCredentials();
The backend team mentioned that I would need to use the GetCredentialsForIdentity method, but I can't find anything like that on the Cognito Android SDK.
Any help is appreciated.

The class you should be using is AmazonCognitoIdentityClient, that is the class implementing the GetCredentialsForIdentity API.

When credentialsProvider.getCredentials(); is invoked, the internal AmazonCognitoIdentityClient calls GetCredentialsForIdentity to get new credentials from Cognito.
The Invalid login token error is returned by the service if the provided token has expired.

Having trouble implementing Stormpath form Login/Authentication alongside REST oAuth authentication in the same application

We're using stormpath with Java & also trying to combine form Login with REST API authentication on the same application.
I've setup stormpath servlet plugin as described here https://docs.stormpath.com/java/servlet-plugin/quickstart.html... This works very fine.
Now, on the same application, we have APIs where I've implemented oAuth authentication with stormpath see here http://docs.stormpath.com/guides/api-key-management/
The first request for an access-token works fine by sending Basic Base64(keyId:keySecret) in the request header and grant_type = client_credentials in the body. Access tokens are being returned nicely. However trying to authenticate subsequent requests with the header Bearer <the-obtained-access-token> does not even hit the application before
returning the following json error message...
{
"error": "invalid_client",
"error_description": "access_token is invalid."
}
This is confusing because I've set breakpoints all over the application and I'm pretty sure that the API request doesn't hit the anywhere within the application before stormpath kicks in and returns this error. And even if stormpath somehow intercepts the request before getting to the REST interface, this message doesn't make any sense to me because i'm certainly making the subsequent API calls with a valid access-token obtained from the first call to get access-token.
I have run out of ideas why this could be happening but i'm suspecting that it may have something to do with stormpath config especially with a combination
of form Login/Authentication for web views and oAuth Athentication for REST endpoints. With that said, here's what my stormpath.properties looks like. Hope this could help point at anything I may be doing wrong.
stormpath.application.href=https://api.stormpath.com/v1/applications/[app-id]
stormpath.web.filters.authr=com.app.security.AuthorizationFilter
stormpath.web.request.event.listener = com.app.security.AuthenticationListener
stormpath.web.uris./resources/**=anon
stormpath.web.uris./assets/**=anon
stormpath.web.uris./v1.0/**=anon
stormpath.web.uris./** = authc,authr
stormpath.web.uris./**/**=authc,authr
Help with this would be highly appreciated.

The problem might be related to an incorrect request.
Is it possible for you to try this code in your app?:
private boolean verify(String accessToken) throws OauthAuthenticationException {
HttpRequest request = createRequestForOauth2AuthenticatedOperation(accessToken);
AccessTokenResult result = Applications.oauthRequestAuthenticator(application)
.authenticate(request);
System.out.println(result.getAccount().getEmail() + " was successfully verified, you can allow your protect operation to continue");
return true;
}
private HttpRequest createRequestForOauth2AuthenticatedOperation(String token) {
try {
Map<String, String[]> headers = new LinkedHashMap<String, String[]>();
headers.put("Accept", new String[]{"application/json"});
headers.put("Authorization", new String[]{"Bearer " + token});
HttpRequest request = HttpRequests.method(HttpMethod.GET)
.headers(headers)
.build();
return request;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}

I've prepared an example that demonstrates oauth token creation as well as authorized access to protected pages using access tokens.
It builds off of the servlet example in the Stormpath SDK. The repo can be found here: https://github.com/stormpath/stormpath-java-oauth-servlet-sample
It demonstrates running a servlet application and having an out-of-band program get and use oauth tokens to access protected resources.
The core of the oauth part is in TokenAuthTest.java:
public class TokenAuthTest {
public static void main(String[] args) throws Exception {
String command = System.getProperty("command");
if (command == null || !("getToken".equals(command) || "getPage".equals(command))) {
System.err.println("Must supply a command:");
System.err.println("\t-Dcommand=getToken OR");
System.err.println("\t-Dcommand=getPage OR");
System.exit(1);
}
if ("getToken".equals(command)) {
getToken();
} else {
getPage();
}
}
private static final String APP_URL = "http://localhost:8080";
private static final String OAUTH_URI = "/oauth/token";
private static final String PROTECTED_URI = "/dashboard";
private static void getToken() throws Exception {
String username = System.getProperty("username");
String password = System.getProperty("password");
if (username == null || password == null) {
System.err.println("Must supply -Dusername=<username> -Dpassword=<password> on the command line");
System.exit(1);
}
PostMethod method = new PostMethod(APP_URL + OAUTH_URI);
method.setRequestHeader("Origin", APP_URL);
method.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
method.addParameter("grant_type", "password");
method.addParameter("username", username);
method.addParameter("password", password);
HttpClient client = new HttpClient();
client.executeMethod(method);
BufferedReader br = new BufferedReader(new InputStreamReader(method.getResponseBodyAsStream()));
String readLine;
while(((readLine = br.readLine()) != null)) {
System.out.println(readLine);
}
}
private static void getPage() throws Exception {
String token = System.getProperty("token");
if (token == null) {
System.err.println("Must supply -Dtoken=<access token> on the command line");
System.exit(1);
}
GetMethod method = new GetMethod(APP_URL + PROTECTED_URI);
HttpClient client = new HttpClient();
System.out.println("Attempting to retrieve " + PROTECTED_URI + " without token...");
int returnCode = client.executeMethod(method);
System.out.println("return code: " + returnCode);
System.out.println();
System.out.println("Attempting to retrieve " + PROTECTED_URI + " with token...");
method.addRequestHeader("Authorization", "Bearer " + token);
returnCode = client.executeMethod(method);
System.out.println("return code: " + returnCode);
}
}

Can I develop a Desktop App for LinkedIn using Java?

I was wondering if I can develop a Desktop App for LinkedIn using Java. I know it can be done as a web application easily, but a completely desktop application, is it possible?
I had a look at the linkedin api's and Java Wrapper for LinkedIn.
The code was explained for a web application. How do I manage that in a java desktop app, specifically the authorization part?
oAuth using Swing?
Please direct me in the right way.

After a very long time of testing with oAuth (with my own wrappers), I settled for Scribe which is a Java Wrapper for almost all oAuth mechanisms. To include Linkedin in a Desktop client, as Adam Trachtenberg (Thank you again) suggested, oob option was used, i.e., after logging in, a code generated by linkedin has to be entered in our Client so that it can be validated against the requested url. Hope this is useful for someone.
public class LinkedInExample
{
private static final String PROTECTED_RESOURCE_URL = "http://api.linkedin.com/v1/people/~/connections:(id,last-name)";
public static void main(String[] args) throws IOException
{
OAuthService service = new ServiceBuilder()
.provider(LinkedInApi.class)
.apiKey("YourApiKey")
.apiSecret("YourApiSecret")
.build();
Scanner in = new Scanner(System.in);
//BareBonesBrowserLaunch.openURL("www.google.com");
System.out.println("=== LinkedIn's OAuth Workflow ===");
System.out.println();
// Obtain the Request Token
System.out.println("Fetching the Request Token...");
Token requestToken = service.getRequestToken();
System.out.println("Got the Request Token!");
System.out.println();
System.out.println("Now go and authorize Scribe here:");
String authURL = service.getAuthorizationUrl(requestToken);
System.out.println(authURL);
BareBonesBrowserLaunch.openURL("www.google.com");
System.out.println("And paste the verifier here");
System.out.print(">>");
Verifier verifier = new Verifier(in.nextLine());
System.out.println();
// Trade the Request Token and Verfier for the Access Token
System.out.println("Trading the Request Token for an Access Token...");
Token accessToken = service.getAccessToken(requestToken, verifier);
System.out.println("Got the Access Token!");
System.out.println("(if your curious it looks like this: " + accessToken + " )");
System.out.println();
// Now let's go and ask for a protected resource!
System.out.println("Now we're going to access a protected resource...");
OAuthRequest request = new OAuthRequest(Verb.GET, PROTECTED_RESOURCE_URL);
service.signRequest(accessToken, request);
Response response = request.send();
System.out.println("Got it! Lets see what we found...");
System.out.println();
System.out.println(response.getBody());
System.out.println();
System.out.println("Thats it man! Go and build something awesome with Scribe! :)");
}
}
The BareBonesBrowserLaunch is used to launch the default browser with the Linkedin URL for the token request in most OS's. Since the Desktop part is not available in Java 1.5, the BareBonesBrowserLaunch solves the problem.
public class BareBonesBrowserLaunch {
static final String[] browsers = { "google-chrome", "firefox", "opera",
"epiphany", "konqueror", "conkeror", "midori", "kazehakase", "mozilla" };
static final String errMsg = "Error attempting to launch web browser";
public static void openURL(String url) {
try { //attempt to use Desktop library from JDK 1.6+
Class<?> d = Class.forName("java.awt.Desktop");
d.getDeclaredMethod("browse", new Class[] {java.net.URI.class}).invoke(
d.getDeclaredMethod("getDesktop").invoke(null),
new Object[] {java.net.URI.create(url)});
//above code mimicks: java.awt.Desktop.getDesktop().browse()
}
catch (Exception ignore) { //library not available or failed
String osName = System.getProperty("os.name");
try {
if (osName.startsWith("Mac OS")) {
Class.forName("com.apple.eio.FileManager").getDeclaredMethod(
"openURL", new Class[] {String.class}).invoke(null,
new Object[] {url});
}
else if (osName.startsWith("Windows"))
Runtime.getRuntime().exec(
"rundll32 url.dll,FileProtocolHandler " + url);
else { //assume Unix or Linux
String browser = null;
for (String b : browsers)
if (browser == null && Runtime.getRuntime().exec(new String[]
{"which", b}).getInputStream().read() != -1)
Runtime.getRuntime().exec(new String[] {browser = b, url});
if (browser == null)
throw new Exception(Arrays.toString(browsers));
}
}
catch (Exception e) {
JOptionPane.showMessageDialog(null, errMsg + "\n" + e.toString());
}
}
}
}
The LinkedInExample is taken mostly from this library - https://github.com/fernandezpablo85/scribe-java/downloads
Don't forget to include the Scribe jar and apache commons-codec (for Base64)

Yes you can it's all about playing with the API and utilizing the web services packed within the LinkedIn's API.
However, the entire process has to be implemented by using the HTTP requests etc and by parsing the response to render it on the JForm.
EDIT: Ahh! you are totally independent :-) thanks to XML..

If you can't figure out how to redirect the user to a web browser and have the browser redirect back to your application, check out the "out of bounds" (aka "oob") option for the OAuth callback. This will display a code to the member after they authorize your application, which they can type into your Java app.

Spring Security & Facebook OAuth 2.0 Integration with Graph API

Please, at least pseudo (but from working environment not "maybe this should work") application context and controller/filter that will authenticate and/or auto-register Facebook users.
This link: http://blog.kadirpekel.com/2009/11/09/facebook-connect-integration-with-spring-security/ will not do. Actually I will put minus point to anyone who will post it as answer. I spend 2 hours with the thing and I didn't get it to work. I ended bit more bolder and feeling more stupid than usual after this endeavor :-(
I would really like to see OAuth 2.0 solution for facebook connect. And restrict the use of Facebook JavaScript API to absolute minimum.
Following link shows about what I need:
http://www.richardnichols.net/2010/06/implementing-facebook-oauth-2-0-authentication-in-java/
Please post only code to this question. I already got all the advice I can handle.
UPDATE
I have servlet solution and posted answer here if anyone is interested:
Facebook Connect example in JSP (tomcat)

Here's an MVC implementation of facebook OAuth 2.0
The code's in C# and hopefully its similarity with java helps you out.
Controller(Entry point):Controller(in MVC) is the point in the code where the control reaches after someone clicks on the login link.
public ActionResult Authenticate()
{
var oauthFacebook = new FacebookOAuth();
if (Request["code"] == null)
{
//Redirect the user to Facebook for authorization.
Response.Redirect(oauthFacebook.AuthorizationLinkGet());
}
else
{
//Get the access token and secret.
oauthFacebook.AccessTokenGet(Request["code"]);
if (oauthFacebook.Token.Length > 0)
{
//We can now make our api calls
var user = oauthFacebook.GetAttributes();
}
}
}
FacebookOAuth Class
public class FacebookOAuth : Oauth
{
public FacebookOAuth()
{
Authorize = "https://graph.facebook.com/oauth/authorize";
AccessToken = "https://graph.facebook.com/oauth/access_token";
CallbackUrl = "http://<YourURLHere>/Authenticate";
AttributesBaseUrl = "https://graph.facebook.com/me/?access_token=";
ConsumerKey = ConfigurationManager.AppSettings["FacebookConsumerKey"];//Ur Consumer Key goes here
ConsumerSecret = ConfigurationManager.AppSettings["FacebookConsumerSecret"];//Ur Consumer secret goes here
Provider = "Facebook";
}
public override string AuthorizationLinkGet()
{
return
string.Format(
"{0}?client_id={1}&redirect_uri={2}&scope=email,user_education_history,user_location,user_hometown",
Authorize, ConsumerKey, CallbackUrl);
}
public User GetAttributes()
{
string attributesUrl = string.Format("{0}{1}", AttributesBaseUrl, Token);
string attributes = WebRequest(Method.Get, attributesUrl, String.Empty);
var FacebookUser = new JavaScriptSerializer().Deserialize<FacebookUser>(attributes);
return new User()
{
FirstName = FacebookUser.first_name,
MiddleName = FacebookUser.middle_name,
LastName = FacebookUser.last_name,
Locale = FacebookUser.locale,
UserEmail = FacebookUser.email,
AuthProvider = Provider,
AuthToken=Token
};
}
}
OAuth baseclass(Class from which FacebookOAuth derives)
public abstract class Oauth
{
#region Method enum
public enum Method
{
Get,
Post,
Delete
} ;
#endregion
protected string AccessToken;
protected string AttributesBaseUrl;
protected string Authorize;
protected string CallbackUrl;
protected string ConsumerKey;
protected string ConsumerSecret;
public string Provider { get; protected set; }
public string Token { get; set; }
public virtual string AuthorizationLinkGet()
{
return
string.Format(
"{0}?client_id={1}&redirect_uri={2}&scope=publish_stream,email,user_education_history,user_location",
Authorize, ConsumerKey, CallbackUrl);
}
public void AccessTokenGet(string authToken)
{
Token = authToken;
string accessTokenUrl = string.Format("{0}?client_id={1}&redirect_uri={2}&client_secret={3}&code={4}",
AccessToken, ConsumerKey, CallbackUrl, ConsumerSecret, authToken);
string response = WebRequest(Method.Get, accessTokenUrl, String.Empty);
if (response.Length > 0)
{
//Store the returned access_token
NameValueCollection qs = HttpUtility.ParseQueryString(response);
if (qs["access_token"] != null)
{
Token = qs["access_token"];
}
}
}
public string WebRequest(Method method, string url, string postData)
{
StreamWriter requestWriter;
string responseData = string.Empty;
var webRequest = System.Net.WebRequest.Create(url) as HttpWebRequest;
if (webRequest != null)
{
webRequest.Method = method.ToString();
webRequest.ServicePoint.Expect100Continue = false;
webRequest.Timeout = 20000;
if (method == Method.Post)
{
webRequest.ContentType = "application/x-www-form-urlencoded";
//POST the data.
requestWriter = new StreamWriter(webRequest.GetRequestStream());
try
{
requestWriter.Write(postData);
}
finally
{
requestWriter.Close();
}
}
responseData = WebResponseGet(webRequest);
}
return responseData;
}
public string WebResponseGet(HttpWebRequest webRequest)
{
StreamReader responseReader = null;
string responseData;
try
{
responseReader = new StreamReader(webRequest.GetResponse().GetResponseStream());
responseData = responseReader.ReadToEnd();
}
finally
{
if (webRequest != null) webRequest.GetResponse().GetResponseStream().Close();
if (responseReader != null) responseReader.Close();
}
return responseData;
}
}

I actually just finished my non-javascript, implementation of the Facebook Graph API Authentication last night. I was a gargantuan pain in the a**, but it works and it's working fairly well.
I used the example from the link you posted above as a starting point, as well as, the code from here as a starting point. I had to write my own implementation of their FacebookGraphAuthenticationProvider and their FacebookGraphAuthenticationFilter, but now it works the way I want it to.
You need to create implementations of both of these files, put your filter in the filter chain, and create a implementation of the Spring Security UserDetailsService that the Provider can use to manage your user account information. I have some code on my machine at home that I can send you via email if you like.
Here are the steps I had to use to get the authentication to work:
Get an "code" for a user, this is done by making the following call: https://www.facebook.com/dialog/oauth?client_id=YOUR_APP_ID&redirect_uri=YOUR_URL&scope=email,read_stream (The scope is all the permissions you want to request from FB). This call will create an "authentication code" which will then be sent back to your "redirect_uri" (which I stated as http://{my fb app registered domain}/j_spring_security_authentication_check.
Once you have this "code", you need to make a call within your AuthenticationProvider that will retrieve an access_token for your user's session: this URL looks like: https://graph.facebook.com/oauth/access_token? client_id=YOUR_APP_ID&redirect_uri=YOUR_URL&client_secret=YOUR_APP_SECRET&code=THE_CODE_FROM_ABOVE. You have to make sure your "redirect_uri" is the same as the one you did in #1. You'll make the above call using something like Apache's HttpClient, or the like.
Now with this access_token (which comes in the body of above response), you can get your user's profile information with the following URL: https://graph.facebook.com/me?access_token={ACCESS_TOKEN from above). The response will be in JSON. You can also use the access_token with all of the graph API to post status, pictures, etc.
I have some code at home that has my full implementation that I would be happy to share.
I hope this helps at least a bit. I suggest using the Spring Social app to get started with posting status, pictures, wall stuff, etc. This will be a good place to start looking at FB-Spring interaction.