Develop Reference

Java - Retrieving a web page with authorization

I'm trying to retrieve a github web page using a java code, for this I used following code.
String startingUrl = "https://github.com/xxxxxx";
URL url = new URL(startingUrl );
HttpURLConnection uc = (HttpURLConnection) url.openConnection();
uc.connect();
String line = null;
StringBuffer tmp = new StringBuffer();
try{
BufferedReader in = new BufferedReader(new InputStreamReader(uc.getInputStream(), "UTF-8"));
while ((line = in.readLine()) != null) {
tmp.append(line);
}
}catch(FileNotFoundException e){
}
However, the page I received here is different from what I observe in browser after login to github. I tried sending authorization header as following, but it didn't worked either.
uc.setRequestProperty("Authorization", "Basic encodexxx");
How can I retrieve the same page that I see when I logged in?

I can't tell you more on this, because I don't know what are you getting, but most common issue for web crawlers is the fact that website owners mostly don't like web crawlers. Thus, you should behave like regular user - your browser for instance. Open your browser inspection element (press f12) when you are reaching some website and see what your browser send in request, then try to mimic it: For example, add Host, Referer, etc in your header. You need to experiment on this.
Also, good to know - some website owners will use advanced techniques (so they will block you to access their site), some won't stop you crawling on their website. Some will let you do what you want. Most fair option is to check www.somedomain.com/robots.txt and there is list of endpoints that are allowed for scraping and those that shouldn't be allowed.

How to get access token using gmail api

I got the authorization code following this document. But when I tried to get access token, I always got errors. Can anyone help me ?
public String AccessToken()
{
String accessToken = "";
StringBuilder strBuild = new StringBuilder();
String authURL = "https://accounts.google.com/o/oauth2/token?";
String code = "4/SVisuz_x*********************";
String client_id = "******************e.apps.googleusercontent.com";
String client_secret = "*******************";
String redirect_uri = "urn:ietf:wg:oauth:2.0:oob";
String grant_type="authorization_code";
strBuild.append("code=").append(code)
.append("&client_id=").append(client_id)
.append("&client_secret=").append(client_secret)
.append("&redirect_uri=").append(redirect_uri)
.append("&grant_type=").append(grant_type);
System.out.println(strBuild.toString());
try{
URL obj = new URL(authURL);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setDoOutput(true);
con.setRequestMethod("POST");
con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
con.setRequestProperty("Host", "www.googleapis.com");
//BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(con.getOutputStream()));
//bw.write(strBuild.toString());
//bw.close();
DataOutputStream wr = new DataOutputStream(con.getOutputStream());
wr.writeBytes(strBuild.toString());
wr.flush();
wr.close();
//OutputStreamWriter out = new OutputStreamWriter(con.getOutputStream());
System.out.println(con.getResponseCode());
System.out.println(con.getResponseMessage());
} catch (Exception e)
{
System.out.println("Error.");
}
return "";
}
when I ran this code, the output is:
400
Bad Request

How to get access token using gmail api?
Ans: As per your following tutorial, you are using OAuth 2.0. So there is a basic pattern for accessing a Google API using OAuth 2.0. It follows 4 steps:
Obtain OAuth 2.0 credentials from the Google Developers Console.
Obtain an access token from the Google Authorization Server.
Send the access token to an API.
Refresh the access token, if necessary.
For details, you can follow the tutorial - Using OAuth 2.0 to Access Google APIs
You have to visit the Google Developers Console to obtain OAuth 2.0 credentials such as a client ID and client secret that are known to both Google and your application
Root Cause Analysis:
Issue-1:
After studying your code, some lacking are found. If your code runs smoothly, then the code always give an empty string. Because your AccessToken() method always return return "";
Issue-2:
catch (Exception e)
{
System.out.println("Error.");
}
Your try catch block is going exception block. Because, it seems that you have not completed your code properly. You have missed encoding as well as using JSONObject which prepares the access token. So it is giving output as
Error.
Solution:
I got that your code is similar with this tutorial
As your code needs more changes to solve your issue. So I offer you to use LinkedHashMap or ArrayList. Those will provide easier way to make solution. So I give you 2 sample code to make your life easier. You can choose any of them. You need to change refresh_token, client id, client secret and grant type as yours.
private String getAccessToken()
{
try
{
Map<String,Object> params = new LinkedHashMap<>();
params.put("grant_type","refresh_token");
params.put("client_id",[YOUR CLIENT ID]);
params.put("client_secret",[YOUR CLIENT SECRET]);
params.put("refresh_token",[YOUR REFRESH TOKEN]);
StringBuilder postData = new StringBuilder();
for(Map.Entry<String,Object> param : params.entrySet())
{
if(postData.length() != 0)
{
postData.append('&');
}
postData.append(URLEncoder.encode(param.getKey(),"UTF-8"));
postData.append('=');
postData.append(URLEncoder.encode(String.valueOf(param.getValue()),"UTF-8"));
}
byte[] postDataBytes = postData.toString().getBytes("UTF-8");
URL url = new URL("https://accounts.google.com/o/oauth2/token");
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());
String accessToken = json.getString("access_token");
return accessToken;
}
catch (Exception ex)
{
ex.printStackTrace();
}
return null;
}
For accessing google play android developer api, you need to pass the
previous refresh token to get access token
private String getAccessToken(String refreshToken){
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost("https://accounts.google.com/o/oauth2/token");
try
{
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(4);
nameValuePairs.add(new BasicNameValuePair("grant_type", "refresh_token"));
nameValuePairs.add(new BasicNameValuePair("client_id", GOOGLE_CLIENT_ID));
nameValuePairs.add(new BasicNameValuePair("client_secret", GOOGLE_CLIENT_SECRET));
nameValuePairs.add(new BasicNameValuePair("refresh_token", refreshToken));
post.setEntity(new UrlEncodedFormEntity(nameValuePairs));
org.apache.http.HttpResponse response = client.execute(post);
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
StringBuffer buffer = new StringBuffer();
for (String line = reader.readLine(); line != null; line = reader.readLine())
{
buffer.append(line);
}
JSONObject json = new JSONObject(buffer.toString());
String accessToken = json.getString("access_token");
return accessToken;
}
catch (IOException e) { e.printStackTrace(); }
return null;
}
Resource Link:
Unable to get the subscription information from Google Play Android Developer API
Using java.net.URLConnection to fire and handle HTTP requests
How to send HTTP request GET/POST in Java
Hope that, this samples and resource link will help you to solve your issue and get access of access token.
What is 400 bad request?
Ans: It indicates that the query was invalid. Parent ID was missing or the combination of dimensions or metrics requested was not valid.
Recommended Action: You need to make changes to the API query in order for it to work.
For HTTP/1.1 400 Bad Request error, you can go through my another
answer. It will help you to make sense about which host you
need to use and which conditions you need to apply.
Why token expires? What is the limit of token?
A token might stop working for one of these reasons:
The user has revoked access.
The token has not been used for six months.
The user changed passwords and the token contains Gmail, Calendar,
Contacts, or Hangouts scopes.
The user account has exceeded a certain number of token requests.
There is currently a limit of 25 refresh tokens per user account per client. If the limit is reached, creating a new token automatically invalidates the oldest token without warning. This limit does not apply to service accounts.
Which precautions should be followed?
Precautions - 1:
Some requests require an authentication step where the user logs in
with their Google account. After logging in, the user is asked whether
they are willing to grant the permissions that your application is
requesting. This process is called user consent.
If the user grants the permission, the Google Authorization Server
sends your application an access token (or an authorization code that
your application can use to obtain an access token). If the user does
not grant the permission, the server returns an error.
Precautions - 2:
If an access token is issued for the Google+ API, it does not grant
access to the Google Contacts API. You can, however, send that access
token to the Google+ API multiple times for similar operations.
Precautions - 3:
An access token typically has an expiration date of 1 hour, after
which you will get an error if you try to use it. Google Credential
takes care of automatically "refreshing" the token, which simply means
getting a new access token.
Save refresh tokens in secure long-term storage and continue to use
them as long as they remain valid. Limits apply to the number of
refresh tokens that are issued per client-user combination, and per
user across all clients, and these limits are different. If your
application requests enough refresh tokens to go over one of the
limits, older refresh tokens stop working.

You are not using the right endpoint. Try to change the authURL to https://www.googleapis.com/oauth2/v4/token
From the documentation:
To make this token request, send an HTTP POST request to the /oauth2/v4/token endpoint
The actual request might look like the following:
POST /oauth2/v4/token HTTP/1.1
Host: www.googleapis.com
Content-Type: application/x-www-form-urlencoded
code=4/v6xr77ewYqhvHSyW6UJ1w7jKwAzu&
client_id=8819981768.apps.googleusercontent.com&
client_secret=your_client_secret&
redirect_uri=https://oauth2-login-demo.appspot.com/code&
grant_type=authorization_code
Reference https://developers.google.com/identity/protocols/OAuth2InstalledApp#handlingtheresponse

For me your request is fine, I tried it using Curl, I also get a 'HTTP/1.1 400 Bad Request' with the reason why it failed 'invalid_grant' :
curl -X POST https://www.googleapis.com/oauth2/v4/token -d 'code=4/SVisuz_x*********************&client_id=*******************7vet.apps.googleusercontent.com&client_secret=***************&redirect_uri=https://oauth2-login-demo.appspot.com/code&grant_type=authorization_code'
I receive (HTTP/1.1 400 Bad Request) :
{
"error": "invalid_grant",
"error_description": "Code was already redeemed."
}
Now using HttpClient from Apache :
URL obj = new URL(authURL);
HttpClient client = HttpClientBuilder.create().build();
HttpPost post = new HttpPost(authURL);
post.addHeader("Content-Type", "application/x-www-form-urlencoded");
post.addHeader("Host", "www.googleapis.com");
post.setEntity(new StringEntity(strBuild.toString()));
HttpResponse resp = client.execute(post);
System.out.println(resp.getStatusLine());
System.out.println(EntityUtils.toString(resp.getEntity()));
I see in my console :
HTTP/1.1 400 Bad Request
{
"error": "invalid_grant",
"error_description": "Code was already redeemed."
}
Are you sure the code you are using is still valid ? Can you try with a new one ?

Firstly, you must look this page :
https://developers.google.com/gmail/api/auth/web-server#create_a_client_id_and_client_secret
The value you see in the query parameter code is a string you have to post to google in order to get the access token.
After the web server receives the authorization code, it may exchange the authorization code for an access token and a refresh token. This request is an HTTPS POST to the URL https://www.googleapis.com/oauth2/v3/token
POST /oauth2/v3/token HTTP/1.1
content-type: application/x-www-form-urlencoded
code=4/v4-CqVXkhiTkn9uapv6V0iqUmelHNnbLRr1EbErzkQw#&redirect_uri=&client_id=&scope=&client_secret=************&grant_type=authorization_code
https://developers.google.com/identity/protocols/OAuth2WebServer

I think I understand what's wrong:
as #newhouse said, you should POST to https://www.googleapis.com/oauth2/v4/token and not https://accounts.google.com/o/oauth2/token (#newhouse I gave you a +1 :) )
(https://www.googleapis.com/oauth2/v4/token is for getting the authorization_code and https://accounts.google.com/o/oauth2/token is for getting the code).
You can't use the same code more than once.
Everything else seems in order so, if you keep getting 400, you are probably trying to use the code you got more than one time (then you'll get 400 every time, again and again).
* You should also lose the con.setRequestProperty("Host", "www.googleapis.com");

Refer : https://developers.google.com/android-publisher/authorization
You already have authorization code that is called "refresh token". Please keep it in safe place. You can use "refresh token" to generate "access token".
To get "access token", please make a post request to following URL
https://accounts.google.com/o/oauth2/token
Parameters:
grant_type
client_id
client_secret
refresh_token
where "grant_type" should be "refresh_token"
We are using PHP to do same, here is PHP's code for your reference
$curl = curl_init();
curl_setopt_array($curl, array(
CURLOPT_RETURNTRANSFER => 1,
CURLOPT_URL => 'https://accounts.google.com/o/oauth2/token',
CURLOPT_USERAGENT => 'Pocket Experts Services',
CURLOPT_POST => 1,
CURLOPT_POSTFIELDS => array(
"grant_type" => "refresh_token",
"client_id" => $GOOGLE_CLIENT_ID,
"client_secret" => $GOOGLE_CLIENT_SECRET,
"refresh_token" => $GOOGLE_REFRESH_TOKEN,
)));
// Send the request & save response to $resp
$resp = curl_exec($curl);
Hope it will help you.

the low security methode was temporary and i couldn't use it in production but I found an article that made it easier using node here
with an example code and it works perfect

Digest authentication in Android using HttpURLConnection

as the question allready says, I am trying to do digest authentication in android.
Until now i have used the DefaultHttpClient and it's authentication method (using UsernamePasswordCredentials and so on), but it is deprecated since Android 5 and will be removed in Android 6.
So i am about to switch from DefaultHttpClient to HttpUrlConnection.
Now i am trying to achieve digest authentication, which should work pretty simple as explained here:
Authenticator.setDefault(new Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(username, password);
}
});
But the getPasswordAuthentication gets never called for some reason.
During my search for this problem i found different posts, saying digest authentication is not supported by the HttpUrlConnection in android, but those posts are from 2010-2012, so i am not sure if this is still true. Also we are using HttpUrlConnection with digest authentication in our desktop java application, where it does work.
I also found some posts, talking about OkHttp. OkHttp seems to be used by Android under the hood (to be more specific the HttpUrlConnectionImpl). But this HttpUrlConnectionImpl is a bit strange, it is not even shown in the Eclipse type hierarchy and i am not able to debug it. Also it should be a com.squareup.okhttp.internal.huc.HttpUrlConnectionImpl, while in android it is a com.android.okhttp.internal.http.HttpUrlConnectionImpl.
So i am just not able to do digest authentication with this HttpUrlConnection in android.
Can anyone tell me how to do that without external libraries?
EDIT:
The server asks for digest authentication:
WWW-Authenticate: Digest realm="Realm Name",domain="/domain",nonce="nonce",algorithm=MD5,qop="auth"
So Basic-Authentication shouldn' work, as the server is asking for digest.

The answer is, that HttpUrlConnection does not support digest.
You therefore have to implement RFC2617 by yourself.
You can use the following code as a baseline implementation: HTTP Digest Auth for Android.
The steps involve (see RFC2617 for reference):
If you get a 401 response, iterate over all WWW-Authenticate headers and parse them:
Check if algorithm is MD5 or undefined, (optionally select the auth qop option), otherwise ignore the challenge and go to the next header.
Get the credentials using Authenticator.requestPasswordAuthentication.
Calculate H(A1) using the username, realm and password.
Store the canonical root URL, realm, HA1, username, nonce (+ optionally algorithm, opaque and the client selected qop option if present).
Retry the request.
On each request, iterate over all realms you have session information stored for by canonical root URL:
Calculate H(A2) using the request method and path.
Calculate H(A3) using HA1, nonce (+ optionally nc, cnonce, qop) and HA2.
Build and add the Authorization header to your HttpUrlConnection.
Implement some sort of session pruning.
By using Authenticator, you can make sure, that as soon as HttpUrlConnection supports digest natively, your code is not being used anymore (because you wont receive the 401 in the first place).
This is just a quick summary on how to implement it, for you to get an idea.
If you want to go further you would probably like to implement SHA256 as well: RFC7616

It is correct that HttpUrlConnection does not support Digest authentication. If your client must authenticate using Digest, you have a few options:
Write your own HTTP Digest implementation. This can be a good option if you know which servers that you need to authenticate with and can ignore the parts of the the digest specification that you do not need. Here is an example where a subset of digest is implemented: https://gist.github.com/slightfoot/5624590.
Use the external lib bare-bones-digest, which is a Digest lib for Android. You can use it to parse Digest challenges and generate responses to them. It supports the common digest use cases and some of the rarely used ones and can be used on top of HttpURLConnection.
Use OkHttp together with okhttp-digest, which is a plugin that adds Http Digest support to OkHttp. Supporting Digest with OkHttp is easy, just add okhttp-digest as an authenticator and you will have transparent Http digest support. If you already use OkHttp or are OK with switching to it this can be an attractive option.
Use the Apache HttpClient which supports Digest. The question explicitly states that HttpClient is not an option so I include it mostly for completion's sake. Google does not recommend using HttpClient and has deprecated it.

Did you try to set the header manually like:
String basic = "Basic " + new String(Base64.encode("username:password".getBytes(),Base64.NO_WRAP ));
connection.setRequestProperty ("Authorization", basic);
Also be aware of some issues in Jellybeans and a bug when you try to perform a post request: HTTP Basic Authentication issue on Android Jelly Bean 4.1 using HttpURLConnection
EDIT: For Digest authentication
Have a look here https://code.google.com/p/android/issues/detail?id=9579
Especially this might work:
try {
HttpClient client = new HttpClient(
new MultiThreadedHttpConnectionManager());
client.getParams().setAuthenticationPreemptive(true);
Credentials credentials = new UsernamePasswordCredentials("username", "password");
client.getState().setCredentials(AuthScope.ANY, credentials);
List<String> authPrefs = new ArrayList<String>(2);
authPrefs.add(AuthPolicy.DIGEST);
authPrefs.add(AuthPolicy.BASIC);
client.getParams().setParameter(AuthPolicy.AUTH_SCHEME_PRIORITY,
authPrefs);
GetMethod getMethod = new GetMethod("your_url");
getMethod.setRequestHeader("Accept", "application/xml");
client.executeMethod(getMethod);
int status = getMethod.getStatusCode();
getMethod.setDoAuthentication(true);
System.out.println("status: " + status);
if (status == HttpStatus.SC_OK) {
String responseBody = getMethod.getResponseBodyAsString();
String resp = responseBody.replaceAll("\n", " ");
System.out.println("RESPONSE \n" + resp);
}
} catch (Exception e) {
e.printStackTrace();
}

I finally replaced the deprecated DefaultHttpClient with my own implementation of the HttpUrlConnection and I implemented digest atuhentication myself, using this as a template.
The finaly code looks something like this:
// requestMethod: "GET", "POST", "PUT" etc.
// Headers: A map with the HTTP-Headers for the request
// Data: Body-Data for Post/Put
int statusCode = this.requestImpl(requestMethod, headers, data);
if (statusCode == HttpURLConnection.HTTP_UNAUTHORIZED && hasUserNameAndPassword) {
String auth = getResponseHeaderField("WWW-Authenticate");
// Server needs Digest authetication
if(auth.startsWith("Digest")){
// Parse the auth Header
HashMap<String, String> authFields = parseWWWAuthenticateHeader(auth);
// Generate Auth-Value for request
String requestAuth = generateDigestAuth(authFields);
headers.put("Authorization", authStr);
statusCode = this.requestImpl(requestMethod, headers, data);
}
}
So basicly I make a request and if it returns 401, I look, if the server wants digest authentication and if I have username and password. If thats the case, I parse the auth header of the response, which contains all the necessary informations about the authentication.
To parse the auth header I use some kind of StateMachine which is described here.
After parsing the response auth header, I generate the request auth header using the informations from the response:
String digestAuthStr = null;
String uri = getURL().getPath();
String nonce = authFields.get("nonce");
String realm = authFields.get("realm");
String qop = authFields.get("qop");
String algorithm = authFields.get("algorithm");
String cnonce = generateCNonce();
String nc = "1";
String ha1 = toMD5DigestString(concatWithSeparator(":", username, realm, password));
String ha2 = toMD5DigestString(concatWithSeparator(":", requestMethod, uri));
String response = null;
if (!TextUtils.isEmpty(ha1) && !TextUtils.isEmpty(ha2))
response = toMD5DigestString(concatWithSeparator(":", ha1, nonce, nc, cnonce, qop, ha2));
if (response != null) {
StringBuilder sb = new StringBuilder(128);
sb.append("Digest ");
sb.append("username").append("=\"").append(username).append("\", ");
sb.append("realm").append("=\"").append(realm).append("\", ");
sb.append("nonce").append("=\"").append(nonce).append("\", ");
sb.append("uri").append("=\"").append(uri).append("\", ");
sb.append("qop").append("=\"").append(qop).append("\", ");
sb.append("nc").append("=\"").append(nc).append("\", ");
sb.append("cnonce").append("=\"").append(cnonce).append("\"");
sb.append("response").append("=\"").append(response).append("\"");
sb.append("algorithm").append("=\"").append(algorithm).append("\"");
digestAuthStr = sb.toString();
}
To generate the Client-Nonce I am using the following code:
private static String generateCNonce() {
String s = "";
for (int i = 0; i < 8; i++)
s += Integer.toHexString(new Random().nextInt(16));
return s;
}
I hope this helps someone. If the code contains any errors, please let me know so I can fix it. But right now it seems to work.

For Android, I found the bare-bones-digest library worked well: https://github.com/al-broco/bare-bones-digest
Add one line to build.gradle
Use the example code at the above url
Works!

Unable to connect to omniture rest API 1.4

We are trying to connect to omniture rest API 1.4 using Java for report.Get. We are unable to create connection. The user id and password are working fine on UI but while making HTTP connection we are getting 400 bad request. Same code works fine with rest API 1.3 for company.reportSuites method. Code if failing while creating input stream. We did checked HTTP response code for connection at it is also coming 400.
public class OMTR_REST {
private static String USERNAME = "XXXXXXX";
private static String PASSWORD = "xXXXXXXXX";
private static String ENDPOINT = "https://api.omniture.com/admin/1.4/rest/"; //san jose endpoint, change for your company's datacenter
private OMTR_REST() {}
public static String callMethod(String method, String data) throws IOException {
URL url = new URL(ENDPOINT + "?method=" + method);
URLConnection connection = url.openConnection();
connection.addRequestProperty("X-WSSE", getHeader());
connection.setDoOutput(true);
OutputStreamWriter wr = new OutputStreamWriter(connection.getOutputStream());
wr.write(data);
wr.flush();
InputStream in = connection.getInputStream();
BufferedReader res = new BufferedReader(new InputStreamReader(in, "UTF-8"));
StringBuffer sBuffer = new StringBuffer();
String inputLine;
while ((inputLine = res.readLine()) != null)
sBuffer.append(inputLine);
res.close();
return sBuffer.toString();

There was a change in the API from version 1.3 to 1.4. The Get method now returns a status of 400 if the report in not ready. To me, it was a bad choice to return a HTTP 400 error (Bad request) when the report in not ready but that is what they are doing. See page 13 in the document below.
https://github.com/AdobeDocs/analytics-1.4-apis

I see few mistakes in your sample:
you should not use api.omniture.com for every request. First request should call api.omniture.com using Company.GetEndpoint method in order to get the correct endpoint, then use it for next requests.
when a wrong endpoint is used you could receive an HTTP 301 response. I'm not sure your implementation handle this case.
when you receive a HTTP 400 error (bad request). Well, that's exactly what has happened, in your example you're JSON writing directly into the body and many things could go wrong. Wrong type for a value, wrong upper/lower case for a key. Using a JAX-RS or another REST client should make your life simpler.
I have built a working Omniture REST API sample with JAX-RS where the model is clear easy to debug/modify.
Update
Recently I have found this:
https://github.com/Adobe-Marketing-Cloud/analytics-java-library

How do I use OAuth with Imgur?

So I am trying to get information of various images, for which I will use the Imgur API through Java.
I have found a library: https://github.com/fernandezpablo85/scribe-java,
but when trying the ImgUrTest.java # https://github.com/fernandezpablo85/scribe-java/blob/master/src/test/java/org/scribe/examples/ImgUrExample.java, I get the following stacktrace:
Exception in thread "main" org.scribe.exceptions.OAuthException: Response body is incorrect. Can't extract token and secret from this: 'OAuth Verification Failed: The consumer_key "<Client-ID>" token "" combination does not exist or is not enabled.'
at org.scribe.extractors.TokenExtractorImpl.extract(TokenExtractorImpl.java:41)
at org.scribe.extractors.TokenExtractorImpl.extract(TokenExtractorImpl.java:27)
at org.scribe.oauth.OAuth10aServiceImpl.getRequestToken(OAuth10aServiceImpl.java:64)
at org.scribe.oauth.OAuth10aServiceImpl.getRequestToken(OAuth10aServiceImpl.java:40)
at org.scribe.oauth.OAuth10aServiceImpl.getRequestToken(OAuth10aServiceImpl.java:45)
at ImgUrExample.main(ImgUrExample.java:31)
where <Client-ID> is my client id, as found on ImgUr's page.
I have checked that my Client Id and Client Secret are correct, I have tried making multiple apps on the ImgUr site, none of which work.
Edit: This code works:
URL imgURL = new URL(YOUR_REQUEST_URL);
HttpURLConnection conn = (HttpURLConnection) imgURL.openConnection();
conn.setRequestMethod("GET");
if (accessToken != null) {
conn.setRequestProperty("Authorization", "Bearer " + accessToken);
} else {
conn.setRequestProperty("Authorization", "Client-ID " + CLIENT_ID);
}
BufferedReader bin = null;
bin = new BufferedReader(new InputStreamReader(conn.getInputStream()));

First, the example is using Imgur API v2 which is old and unsupported. You should be using API v3.
Also note that:
For public read-only and anonymous resources, such as getting image
info, looking up user comments, etc. all you need to do is send an
authorization header with your client_id in your requests.
from docs at https://api.imgur.com/oauth2 -- so you don't really need OAuth for what you're doing.
There is some example Imgur API code that might help you, listed at https://api.imgur.com/ -- the Android example might be more relevant to you, since it uses Java, but unsurprisingly it comes with all the overhead of an Android project, compared with a plain Java application.