We Keep Coding

Spring controller method called twice

I'm making a Spring MVC web app.
The problem is that on single method is called twice and I don't know why.
#RequestMapping(value="/profile/{id}", method = RequestMethod.GET)
public String displayUserProfile( #PathVariable String id) {
System.out.println("asdasddsasd");
return "account/userProfile";
}
I commented many line from this method, but is still not working. Also tried to return other view..no good luck.
In console(ulr requests are written):
/demo/account/profile/f91b3a38-6921-41e0-98b7-58dff5cb1152
asdasddsasd
/demo/account/profile/0
asdasddsasd
After the second call of tihs method, it's going to my view
Any other method work fine.
Does anyone know what's the problem here?
*I also read similar question from here..nothing helped
LE: what I also said in the comments.
What is funny is that, if I set o model to the view, on the second call of the method, my view get's the model from the first call. (on the second call, with id 0, the model is null)

I have also observed one GET request causing the controller method to execute twice. The problem occurred when requesting the service using a Chrome browser (the problem did not occur when using Postman). In my case the culprit was the JSONView Chrome extension.
I determined the cause by using the Network tab of the Chrome developer tools. It showed my GET service being requested two times. The second request was initiated by content.js, which is a JavaScript file bundled with JSONView.
After I disabled the JSONView extension, a GET request through Chrome would cause the controller method to execute only once.

I experienced this called-twice phenomenon because BrowserSync replayed HTTP requests in each open BrowserSync browser window.

I finally got some time to find a solution here.
Tried many things, but it didn't worked.
I replaced #PathVariable with #RequestParam and the URL is not accessed twice :)

Had the same problem.
Eventually I found that I have a null in a background-image url like so:
style="background-image: url(null);"
that caused to send another GET with a path variable null.

I have the same problem and find a lot of solution and finally I found the simple reason. It's in my html template css: background:url() .
This cold will run the same url again. So I just remove it out or put url in the bracket and it works.

Sounds like an issue on client side.
Open up your browser, enter <host/port/whatever_you_need_to access_the_app>/demo/account/profile/f91b3a38-6921-41e0-98b7-58dff5cb1152
and check the logs. The chances are that you'll see only one entry
Now run your client code and check network requests to the service. If you're call the controller from the browser like Chrome F12->Network tab should help.
I know it's a kind of obvious, but I think there is nothing really "unusual" in this controller, so it should be more at the level of general flow. In this case maybe it's the best to trace the HTTP traffic and see how many/when/how does it generate requests to your controller.

This might also occur due to one more reason. Because i found samething and observed following.
1st time its when your request processed and you see println statement in Console.
And if you refresh browser at method request of controller method ( example http://localhost:8080/DemoMVC/add?***) each refresh your tomcat processes request again and you get same println statement in console.

Perhaps this is too late. However, I still face these issues and forget the solution every time.
In case you are using any JS library like Angular or React then in your service call observe the response as well.
Here is a code snippet
return this.http.get<User>(`${this.resourceUrl}/activate`, { params: options, observe: 'response' })
.pipe(
filter((response: HttpResponse<User>) => response.ok),
map((response: HttpResponse<User>) => response.body),
catchError(error => {
return of(error)
})
);
The key area to focus is { params: options, observe: 'response' }

I had a controller which was listening to localhost/ and a get method which matched on a path variable something like this:
#GetMapping("/{foo}")
String get(#PathVariable(required = false) String foo)
{
return "hello world";
}
And the problem was, that after calling localhost/ I got the first call, and after that, I got the second call for the favicon.
The same would be true if you would define a context root.

RuntimeException does not halt GAE but returns HTTP 500 when run locally

Let me first provide some background information. If you don't care you can skip to the next paragraph. I wanted to use the DrEdit sample Java application which is integrated with Google Drive as the basis of my application. I need to refactor the code, though, because the original scenario assumed that the user would only access the application through the Drive and never directly. Currently when the latter happens, a RuntimeException is thrown which should not be the case in a normal flow.
Thanks to that issue I stumbled upon a difference between my local environment and the GAE which is manifested when the following code is run:
} catch (CredentialMediator.NoRefreshTokenException e) {
try {
resp.sendRedirect(e.getAuthorizationUrl());
} catch (IOException ioe) {
throw new RuntimeException("Failed to redirect user for authorization");
}
throw new RuntimeException("No refresh token found. Re-authorizing.");
}
When I run this application on GAE, the RuntimeException is thrown (I can see it in the logs) and the sendRedirect is also executed so I get to see the page that should be displayed.
However when I run the same application locally, I get the HTTP 500 error and the RuntimeException is displayed but the sendRedirect is ignored.
So far I haven't been successful in finding an explanation for this behaviour. I would like to know why this is the case and if there are settings that I can change in order to fully replicate the GAE environment locally.

This is how standard defines the sendRedirect(). It actually commits the response so after calling this method you should not be able to change or add to the response. However it does not define what happens if you trigger an exception after redirect.
Anyway, your code is ambiguous on purpose - you should not continue processing the request and throw exceptions after sending redirect. If you have any processing to do, then do it before redirect.
OTOH you should not rely on generic exception handling. Instead install a servlet filter that catches exceptions and return a proper user-readable or device-readable response.

How to capture "send mail" in plugin for IBM Lotus notes

Here is what I am trying to do:
Add a special button to attach files to Notes "New message" window. If files were attached using this button, when email sent, they should be uploaded to the server and link to them added to the email.
My question - is it possible (and how) to capture "send mail" event in the plugin for Lotus Notus?

I don't know how an Eclipse plugin would do this. Furthermore, since Notes can be used off-line -- when it would be impossible to upload files to a server -- it would be better to have code running on the Domino server intercept the mail messages and perform the upload.
Most products that hook mail operations on the server use the Lotus Notes C API's Extension Manager functions to hook the EM_BEFORE notification for the EM_NSFNOTEUPDATE event and check whether the NSFNoteUpdate operation occurred within the server's mail.box files, and then check whether the the message requires special processing (i.e., in your case that would be by looking for a special NotesItem that your button code has inserted into the message). The usual coding method for this is to immediately change the status of the message to put it on hold, preventing the Domino router from attempting to send the message while your code is still working on it. Many products actually have two components - the EM hook DLL and a separate server task that receives a signal from the hook DLL, processes the message, and then releases it from on hold status. This approach keeps your code from tying up router threads while processing large files.
(Note: Newer versions of the Domino server have the ability to use OSGI plugins written in Java instead of using the Notes C API for operations like this. I've not looked into the details of how this might work for operations that process mail messages. )

I sort of figured it out. There is a very nice extension point provided in 8.5 - "com.ibm.notes.mailsend.MailSendAttachmentsDialog", that is specifically exists for custom handling of attachments. You can see it in plugin.xml, in IBM\Lotus\Notes\framework\shared\eclipse\plugins\com.ibm.notes.mailsend_8.5.*.jar.
The only problem is - it handles just attachments and does not have access to anything else. So if somebody figured how to get subject line and the message text from there, please reply.
Update: got it.
NotesUIElement elem = (new NotesUIWorkspace()).getCurrentElement();
if (elem instanceof NotesUIDocument) {
NotesUIDocument doc = ((NotesUIDocument) elem);
String to = doc.getField("EnterSendTo").getText();
String cc = doc.getField("EnterCopyTo").getText();
String bcc = doc.getField("EnterBlindCopyTo").getText();
String subject = doc.getField("Subject").getText();
String body = doc.getField("Body").getText();
....
}

Executing URI commands in Java

One way that Steam lets users launch games and perform many other operations, is by using URI protocols, for example (from Valve developer community):
steam://run/<id> will launch the game that corresponds to the specified ID.
steam://validate/<id> will validate the game files of the specified ID.
How can I get Java to 'run' these? I don't even know what you call it, i.e. do you 'run' URIs, or 'execute' them, or what? Because persumably these URIs don't have anything to return, and the URI class in Java doesn't have anything related to 'executing' them, however URL does, but it doesn't work!
I've tried this:
...
try
{
URI testURI = URI.create("steam://run/240");
URL testURL = joinURI.toURL();
// URL testURL = new URL("steam://run/240") doesn't work either
joinURL.openConnection(); // Doesn't work
// joinURL.openStream() doesn't work either
}
catch (MalformedURLException e)
{
System.err.println(e.getMessage());
}
...
Each combination gives the error: unknown protocol: steam.
The system that Steam uses to handle the URIs is definitely working, because for example, I can type the above URI into Firefox and it works.
My eternal gratitude to the person who provides the answer!
Thanks

Try Desktop.browse(URI), this should start the "default action" which is the Steam client for a steam:// URI, e.g.
URI uri = new URI("steam://store/240");
if (Desktop.isDesktopSupported()) {
Desktop.getDesktop().browse(uri);
}

The system that Steam uses to handle the URIs is definitely working, because for example, I can type the above URI into Firefox and it works.
It is working because Firefox (or other browsers) can associate unkown protocols with applications. When you load steam://xxx for the first time, Firefox asks you which application you want to open. If it didn't ask you, steam probably installed a browser plugin for that.

A Uniform Resource Identifier (URI) just identifies a resource, it doesn't necessarily describe how to access it. Moreover, for custom protocols, such as "steam" the vendor can define any underlying access conventions which compatible client programs must know to interact.
In order to "execute" a URI like this you need to know exactly how the protocol is implemented (is it over HTTP? TCP? UDP?) and how to speak with the server at the other end.
The Valve Developer Community wiki page might have some useful information.

Can a web service return a stream?

I've been writing a little application that will let people upload & download files to me. I've added a web service to this applciation to provide the upload/download functionality that way but I'm not too sure on how well my implementation is going to cope with large files.
At the moment the definitions of the upload & download methods look like this (written using Apache CXF):
boolean uploadFile(#WebParam(name = "username") String username,
#WebParam(name = "password") String password,
#WebParam(name = "filename") String filename,
#WebParam(name = "fileContents") byte[] fileContents)
throws UploadException, LoginException;
byte[] downloadFile(#WebParam(name = "username") String username,
#WebParam(name = "password") String password,
#WebParam(name = "filename") String filename) throws DownloadException,
LoginException;
So the file gets uploaded and downloaded as a byte array. But if I have a file of some stupid size (e.g. 1GB) surely this will try and put all that information into memory and crash my service.
So my question is - is it possible to return some kind of stream instead? I would imagine this isn't going to be terribly OS independent though. Although I know the theory behind web services, the practical side is something that I still need to pick up a bit of information on.
Cheers for any input,
Lee

Yes, it is possible with Metro. See the Large Attachments example, which looks like it does what you want.
JAX-WS RI provides support for sending and receiving large attachments in a streaming fashion.
Use MTOM and DataHandler in the programming model.
Cast the DataHandler to StreamingDataHandler and use its methods.
Make sure you call StreamingDataHandler.close() and also close the StreamingDataHandler.readOnce() stream.
Enable HTTP chunking on the client-side.

Stephen Denne has a Metro implementation that satisfies your requirement. My answer is provided below after a short explination as to why that is the case.
Most Web Service implementations that are built using HTTP as the message protocol are REST compliant, in that they only allow simple send-receive patterns and nothing more. This greatly improves interoperability, as all the various platforms can understand this simple architecture (for instance a Java web service talking to a .NET web service).
If you want to maintain this you could provide chunking.
boolean uploadFile(String username, String password, String fileName, int currentChunk, int totalChunks, byte[] chunk);
This would require some footwork in cases where you don't get the chunks in the right order (Or you can just require the chunks come in the right order), but it would probably be pretty easy to implement.

When you use a standardized web service the sender and reciever do rely on the integrity of the XML data send from the one to the other. This means that a web service request and answer only are complete when the last tag was sent. Having this in mind, a web service cannot be treated as a stream.
This is logical because standardized web services do rely on the http-protocol. That one is "stateless", will say it works like "open connection ... send request ... receive data ... close request". The connection will be closed at the end, anyway. So something like streaming is not intended to be used here. Or he layers above http (like web services).
So sorry, but as far as I can see there is no possibility for streaming in web services. Even worse: depending on the implementation/configuration of a web service, byte[] - data may be translated to Base64 and not the CDATA-tag and the request might get even more bloated.
P.S.: Yup, as others wrote, "chuinking" is possible. But this is no streaming as such ;-) - anyway, it may help you.

I hate to break it to those of you who think a streaming web service is not possible, but in reality, all http requests are stream based. Every browser doing a GET to a web site is stream based. Every call to a web service is stream based. Yes, all. We don't notice this at the level where we are implementing services or pages because lower levels of the architecture are dealing with this for you - but it is being done.
Have you ever noticed in a browser that sometimes it can take a while to fetch a page - the browser just keeps cranking away showing the hourglass? That is because the browser is waiting on a stream.
Streams are the reason mime/types have to be sent before the actual data - it's all just a byte stream to the browser, it wouldn't be able to identify a photo if you didn't tell it what it was first. It's also why you have to pass the size of a binary before sending - the browser won't be able to tell where the image stops and the page picks up again.
It's all just a stream of bytes to the client. If you want to prove this for yourself, just get a hold of the output stream at any point in the processing of a request and close() it. You will blow up everything. The browser will immediately stop showing the hourglass, and will display a "cannot find" or "connection reset at server" or some other such message.
That a lot of people don't know that all of this stuff is stream based shows just how much stuff has been layered on top of it. Some would say too much stuff - I am one of those.
Good luck and happy development - relax those shoulders!

For WCF I think its possible to define a member on a message as stream and set the binding appropriately - I've seen this work with wcf talking to Java web service.
You need to set the transferMode="StreamedResponse" in the httpTransport configuration and use mtomMessageEncoding (need to use a custom binding section in the config).
I think one limitation is that you can only have a single message body member if you want to stream (which kind of makes sense).

Apache CXF supports sending and receiving streams.

One way to do it is to add a uploadFileChunk(byte[] chunkData, int size, int offset, int totalSize) method (or something like that) that uploads parts of the file and the servers writes it the to disk.

Keep in mind that a web service request basically boils down to a single HTTP POST.
If you look at the output of a .ASMX file in .NET , it shows you exactly what the POST request and response will look like.
Chunking, as mentioned by #Guvante, is going to be the closest thing to what you want.
I suppose you could implement your own web client code to handle the TCP/IP and stream things into your application, but that would be complex to say the least.

I think using a simple servlet for this task would be a much easier approach, or is there any reason you can not use a servlet?
For instance you could use the Commons open source library.

The RMIIO library for Java provides for handing a RemoteInputStream across RMI - we only needed RMI, though you should be able to adapt the code to work over other types of RMI . This may be of help to you - especially if you can have a small application on the user side. The library was developed with the express purpose of being able to limit the size of the data pushed to the server to avoid exactly the type of situation you describe - effectively a DOS attack by filling up ram or disk.
With the RMIIO library, the server side gets to decide how much data it is willing to pull, where with HTTP PUT and POSTs, the client gets to make that decision, including the rate at which it pushes.

Yes, a webservice can do streaming. I created a webservice using Apache Axis2 and MTOM to support rendering PDF documents from XML. Since the resulting files could be quite large, streaming was important because we didn't want to keep it all in memory. Take a look at Oracle's documentation on streaming SOAP attachments.
Alternately, you can do it yourself, and tomcat will create the Chunked headers. This is an example of a spring controller function that streams.
#RequestMapping(value = "/stream")
public void hellostreamer(HttpServletRequest request, HttpServletResponse response) throws CopyStreamException, IOException
{
response.setContentType("text/xml");
OutputStreamWriter writer = new OutputStreamWriter (response.getOutputStream());
writer.write("this is streaming");
writer.close();
}

It's actually not that hard to "handle the TCP/IP and stream things into your application". Try this...
class MyServlet extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)
{
response.getOutputStream().println("Hello World!");
}
}
And that is all there is to it. You have, in the above code, responded to an HTTP GET request sent from a browser, and returned to that browser the text "Hello World!".
Keep in mind that "Hello World!" is not valid HTML, so you may end up with an error on the browser, but that really is all there is to it.
Good Luck in your development!
Rodney