Develop Reference

Java Web Start return value - workaround

I know that returning a value from a JWSapp to the "calling" page cannot be done.
However, I use this JWSapp to get user ID from its biometric information.
The idea is that when you try to login, a button allows to launch the JWSapp that will deal with the biometric tasks and then return the user's idea.
Still, as I said, from a JWSapp I cannot send back the id to auto-complete the field. I found this post: Returning a value from a java web start application but I really need to keep the JWS (external constraints)...
So there's my question: is there any workaround to get the id back?
Thank you in advance :)

Getting Access on the Android VideoView received packets when Streaming a URL

Does the native code of the VideoView give access to the received packets of the video before or after decoding it? I need to access these packets in order to transmit them to another device. The initial solution is to modify the Android native code. Other possible solutions that I found are to use GStreamer or FFmpeg libraries.
I need bit guidance in order to achieve that goal.
Assume the phone is rooted.

Short answer is no, not that I know of.
Long answer is that you haven't given enough detail. What data exactly do you need access to? Are you writing an application, or modifying your OS to do this to other applications?
The code that actually fetches a remote video is in MediaPlayer and is native. See the following method in MediaPlayer:
private void setDataSource(/* snip */) throws /* snip */ {
/* snip */
else if (scheme != null) {
// handle non-file sources
nativeSetDataSource(
MediaHTTPService.createHttpServiceBinderIfNecessary(path),
path,
keys,
values);
return;
}
/* snip */
Unfortunately for you, almost all of the relevant MediaPlayer code is native, and if not, it is private (so subclassing will not work here).
However, depending on what you need to do, you could possibly override VideoView method setVideoURI(Uri, Map<String, String>), which is public. Here you can grab the URI and then proxy it through your own web service, or something. This isn't quite what you were asking, though.
Or, you could possibly look into modifying the Surface that is drawn to by MediaPlayer. Most of the relevant code is still native though.
The final possibility that I'll mention (there are probably hundreds of possible approaches) would be to modify the MediaHTTPService class. This appears to be used by MediaPlayer, but I can't be sure because if it's used, it's used in native code.
This answer recommends finding the native code at androidxref.com
Edit:
As requested, here is a little more detail about what the "proxy server" solution might look like. I don't know the implementation details on Android.
Basically, when you get a URL to play in the VideoView, you pass it to your own server instead. Something like startProxyServer(videoUrl). This starts a server, which downloads and then re-hosts the video. To get this working locally, start a webserver listening on localhost. The server just downloads the video at videoUrl, saves it locally, and then hosts it at localhost:port/?video=${videoUrl}.
So in very high-level pseudo-code the server could look like.
public void startProxyServer(String videoUrl) {
int PORT = 28641; // random port
File f = downloadFile(videoUrl);
saveFile(f, '/path/to/server/storage');
startWebServer('localhost', PORT);
}
So now you give localhost:port/?video=${videoUrl} as url to the videoView instead. Also, now other videoView instances can download from that same localhost url.
To make it work with other phones, your server of course couldn't run on localhost.
Of course I've not implemented this, but it's just one solution I can think of.

ADAL 4 Android not passing client secret

I'll first say that I'm sure it is just me since people have probably got this to work out of the box without having to edit the ADAL 4 Android Library without editing the source.
When running the sample program and authenticating with a token I get an error from AZURE that it is not passing the client_secret in the message body. I can confirm that this is in fact the case - it is not passing the client_secret.
Although if I edit the OAuth2.java file and change the method buildTokenRequestMessage to something like the following the workflow works perfectly
public String buildTokenRequestMessage(String code) throws UnsupportedEncodingException {
String message = String.format("%s=%s&%s=%s&%s=%s&%s=%s&%s=%s",
AuthenticationConstants.OAuth2.GRANT_TYPE,
StringExtensions.URLFormEncode(AuthenticationConstants.OAuth2.AUTHORIZATION_CODE),
AuthenticationConstants.OAuth2.CODE, StringExtensions.URLFormEncode(code),
AuthenticationConstants.OAuth2.CLIENT_ID,
StringExtensions.URLFormEncode(mRequest.getClientId()),
AuthenticationConstants.OAuth2.REDIRECT_URI,
StringExtensions.URLFormEncode(mRequest.getRedirectUri())
// these are the two lines I've added to make it work
AuthenticationConstants.OAuth2.CLIENT_SECRET,
StringExtensions.URLFormEncode("<MY CLIENT SECRET>")
);
return message;
}
Am I doing something wrong? If not, what is the correct way to access the client secret?
My implementation is straight from the demo application with only changes being setting up the strings to match my endpoints.
Thanks

You need to register your app as a Native application at Azure AD portal. You don't need client secret for native app.

how to determine if a web service is up and running

i was trying to call the following web service from my android app, it hung then completed without returning the result:
web service:http://androidexample.com/media/webservice/JsonReturn.php
However when I clicked on the link, it worked fine - the json file displayed. yet it would not work in my app..
but now, it works fine now in my android app, perhaps it was temporarily down is what I am guessing. How can I know if a web service is up and running for an android app to consume ?

Typically, web services are designed to have a status page that can return status text or a HTTP return code to indicate service status.
If it doesn't have that, you can design a function to periodically do a very basic request with a known result to determine state. This is much better than doing a simple ping.

If it was down it would most likely show a HTML error page, which your app would try to parse, which would cause an error.
I had a similar issue, because I needed to know if the user was returning HTML or the correct JSON, to do this I created the ArrayList I was about to use outside of the try/catch of the parse area. You should do the same if you are using a string.
What I mean is, use:
ArrayList<Something> arrayList = new ArrayList<Something>();
String testString = ""; instead of String testString = null;
I was using only ArrayList<Something> arrayList; at one point which is incorrect. If the user then returns HTML, you won't get an error, the user will simply return an empty arraylist or empty string.
You can then plan for that and show some sort of error message. This way you only need one network request but you can still plan for getting the data back, and the server being down.

In java, how can I get an Amazon EC2 Instance to see its own tags?

So I have a java program running within an Amazon EC2 instance. Is there a way to programatically get its own tags? I have tried instantiating a new AmazonEC2Client to us the describeTags() function but it only gives me null. Any help would be appreciated thank you.
Edit: To make things clearer, the instances are going to be unmanned worker machines spun up to solely do some computations

This should help you get started...
String instanceId = EC2MetadataUtils.getInstanceId();
AmazonEC2 client = AmazonEC2ClientBuilder.standard()
.withCredentials(new DefaultAWSCredentialsProviderChain())
.build();
DescribeTagsRequest req = new DescribeTagsRequest()
.withFilters(new Filter("resource-id", Collections.singletonList(instanceId)));
DescribeTagsResult describeTagsResult = client.describeTags(req);
List<TagDescription> tags = describeTagsResult.getTags()

You should be able to get the current instance id by sending a request to: http://169.254.169.254/latest/meta-data/instance-id. This only works within ec2. With this you can access quite a bit of information about the instance. However, tags do not appear to be included.
You should be able to take the instance id along with the correct authentication to get the instance tags. If you are going to run this on an instance, you may want to provide an IAM user with limited access instead of a user which has access to everything in case the instance is compromised.

While using user-data may be the simplest solution, the OP was asking specifically about the tagging, and unfortunately amazon hasn't made this as easy as it could be. However, It can be done. You want to use a combination of 2 amazon services.
First you need to retrieve the Instance ID. This can be achieved by hitting the URL from within your instance:
http://169.254.169.254/latest/meta-data/instance-id
Once you have the resource ID, you'll want to use Amazon's EC2 API to access the tags. Since you said you're using Java, I would suggest the Using the AWS SDK amazon makes available. Within this SDK you'll find a method called describeTags (documentation). You can use a Resource ID as one of the filters to get the specific tags to your instance. Supported filters are
tag key
resource-id
resource-type
I suggest doing this retrieval at boot using something like cloud-init and caching the tags on your server for use later if necessary.