I'm using Vaadin 7.1.2 on a OpenShift instance (RedHat).
OpenShift offers a node.js proxy which should be compatible with WebSocket, but the WebSocket connections get closed immediately after they have been open with no error message (Vaadin just display "connection closed", "wasclean:true", "reason:").
Because there is no error then Vaadin/Atmosphere doesn't fall back to the streaming mode and instead continues to open Websocket once every two seconds.
I'm looking for a way to disable websocket in Vaadin/atmosphere altogether and enable streaming instead.
You can disable websockets and enforce streaming by using the following annotation in your UI class:
#Push(transport = Transport.STREAMING)
public class PushUI extends UI {
...
}
Nowadays the STREAMING transport is deprecated with all Vaadin versions. You should use
#Push(transport = Transport.LONG_POLLING)
instead to use normal HTTP instead of WebSockets.
Related
The documentation says
The JDBC Client API created in Vert.x 3 is now deprecated and instead the new SQL Client API should be used. It will remain supported for the life time of Vert.x 4 to allow applications to be migrated to the new SQL Client API.
It seems that this class works in an Autocommit-Mode. If I have several database calls within one Service, how should this work with transaction-consistency? Is it planned, that the "commit", "rollback" will also be available as it is in SQLConnection?
Thx
You can take a look at Javadocs of the new client transaction APIs in https://vertx.io/docs/apidocs/io/vertx/sqlclient/Pool.html#withTransaction-java.util.function.Function-, the JDBCClient will execute the block starting with disabling auto-commit mode and ending with a commit or rollback execution.
I would like to start websocket connections (ws://whaterver)
in OpenShift but somehow they always ends with ERR_CONNECTION_ABORTED
immediately (new WebSocket('ws://whatever').
First I thought that the problem is in our application
but I created a minimal example and I got the same result.
First I created a pod and started this minimal Python websocket server.
import asyncio
import websockets
async def hello(websocket, path):
name = await websocket.recv()
print(f"< {name}")
greeting = f"Hello {name}!"
await websocket.send(greeting)
print(f"> {greeting}")
start_server = websockets.serve(hello, "0.0.0.0", 8000)
asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_forever()
Then I created a service (TCP 8000) and created a routing too and I got the same result.
I also tried to use different port or different targets (e.g.: /ws), without success.
This minimal script was able to respond to a simple http request, but for the websocket connection it can't.
Do you have any idea what could be the problem?
(by the documentation these connections should work as they are)
Should I try to play with some routing environment variables or are there any limitations which are not mentioned in the documentation?
Posting Károly Frendrich answer as community wiki:
Finally we realized that the TLS termination is required to be set.
It can be done using Secured Routes
I am working on creating a Camel, Spring boot application that implements the OPC-UA connection. Till now, I was successfully able to run the examples obtained from Eclipse milo github repository.
Now, my task is to create a camel route that will connect to the opc-ua server that is running on a different machine, read data from there and store in a jms queue.
Till now, I am able to run the BrowseNodeExample and ReadNodeExample where I am connecting to a server simulator (Top Server V6). In the example code, when connecting to the server, the endpoint of the server is given as - "opc.tcp://127.0.0.1:49384/SWToolbox.TOPServer.V6"
Now in the camel routing piece of code, in the .configure() part, what shall I write in the .from() part. The piece of code is as -
#Override
public void configure() throws Exception {
from("opc.tcp://127.0.0.1:49384/SWToolbox.TOPServer.V6")
.process(opcConnection)
.split(body().tokenize(";"))
.to(opcBean.getKarafQueue());
}
While searching for the solution I came across one option: milo-server:tcp://127.0.0.1:49384/SWToolbox.TOPServer.V6/nodeId=2&namespaceUri=http://examples.freeopcua.github.io. I tried that but it didn't work. In both the cases I get the below error:
ResolveEndpointFailedException: Failed to resolve endpoint: (endpoint
given) due to: No component found with scheme: milo-server (or
opc.tcp)
You might want to add the camel-opc component to your project.
I've found one on Github
and also milo version on maven central for the OPC-UA connection.
Hope that helps :-)
The ResolveEndpointFailedException is quite clear, Camel cannot find the component. That means that the auto-discovery failed to load the definition in the META-INF directory.
Have you checked that the camel-milo jar is contained in your fat-jar/war?
As a workaround you can add the component manualy via
CamelContext context = new DefaultCamelContext();
context.addComponent("foo", new FooComponent(context));
http://camel.apache.org/how-do-i-add-a-component.html
or in your case
#Override
public void configure() throws Exception {
getContext().addComponent("milo-server", new org.apache.camel.component.milo.server.MiloServerComponent());
from("milo-server:tcp://127.0.0.1:49384/SWToolbox.TOPServer.V6/nodeId=2&namespaceUri=http://examples.freeopcua.github.io")
...
}
Furthermore be aware that milo-server starts an OPC UA server. As I understood your question you want to connect to an OPC UA server. Therefore you need the milo-client component.
camel-milo client at github
I am learning to use React at the moment, and I have a problem: I want react to work with my Java Spring Boot backend (Tomcat). React is running on port 3000 (default) and my Tomcat server on port 8080 (default). Now, when I make a REST call, I get the following error
script.js:13 GET http://localhost:8080/api/path?p=test net::ERR_CONNECTION_REFUSED
My rest call looks like:
fetch('http://localhost:8080/api/path?p=test')
.then(res => {
console.log(res);
});
What do I make wrong? I do not really have an idea.
An net::ERR_CONNECTION_REFUSED error is typically thrown when your frontend (React application) cannot connect to your backend (your Spring boot application). There are many possible reasons for this to happen, such as:
Your back-end application is not running
The path to your back-end application is not correct
There is some kind of firewall between your front- and back-end application that is stopping the traffic
...
In your case it appeared to be the back-end application that was not running properly.
Your second problem is related to CORS, which is a mechanism that prevents JavaScript from connecting to other APIs/websites that are not on the same (sub)domain and port. In your case your frontend is running on a different port than you backend, so that means you have to deal with CORS.
To handle CORS, you have to add a header to your backend (namely the Access-Contol-Allow-Origin header the error is mentioning). With Spring, you can do that by adding the following annotation to your controller:
#CrossOrigin(origins = "http://localhost:3000")
Or you can configure CORS globally with a filter or using WebMvcConfigurer:
#Bean
public WebMvcConfigurer corsConfigurer() {
return new WebMvcConfigurerAdapter() {
#Override
public void addCorsMappings(CorsRegistry registry) {
registry.addMapping("/api/**").allowedOrigins("http://localhost:3000");
}
};
}
As mentioned in the comments by #Lutz Horn, this is also described in a Spring guide.
I have been going through the google tutorial ( which I find very good ) at
https://developers.google.com/web-toolkit/doc/latest/tutorial/RPC
I have the service up and running on my local server and my JavaScript client can call it fine. OK so far. Now, what I want to do is deploy the service on a remote server JoeSoapHost:8080
How do I now tell my client where to send it's requests? I can't see any server/url being created in my RPC call. It just works by magic but now I want to get under the bonnet and start breaking it.
[Edit}
This is the Interface my client uses to know what service on the Server is to be called. I know that my Web.xml web descriptor must have a url that matches this. It has this because my server is invoked ok. Problem is, if I now decide to deploy my server elsewhere how do I tell my client what server/domain name to use?
#RemoteServiceRelativePath("stockPrices")
public interface StockPriceService extends RemoteService
{
StockPrice[] getPrices(String[] symbols);
}
What I want to achieve first is have a simple GWT client calling into an RPC service. I have this working but only when the server is localhost.
Next step, I deploy my app to the Google App Engine. What must I change now because my RPC service in my JavaScript is not being called when I deploy my app to
http://stockwatcherjf.appspot.com/StockWatcher.html
1) Brian Slesinsky excellent document on RPC - https://docs.google.com/document/d/1eG0YocsYYbNAtivkLtcaiEE5IOF5u4LUol8-LL0TIKU/edit#heading=h.amx1ddpv5q4m
2) #RemoteServiceRelativePath("stockPrices") allows GWT code to determine relative to your host/server/domain i.e http//mydomain.com/gwtapp/stockPrices
3) You can search GOOGle IO Sessions from 2009 - 2012 for some more in depth stuff on GWT RPC usage.
#RemoteServiceRelativePath gives the path of the servlet relative to the GWT.getModuleBaseURL() (which is more or less the URL of the *.nocache.js script); it doesn't "just work by magic".
If you deploy your services on a different server than the one serving your client code, then you'll likely hit the Same Origin Policy. CORS can help here, but you'll lose compatibility with IE (up to IE9 included). You'd better stick serving everything from the same origin.