I was wondering if there was a way to create a bi-direction stream (or allow multiple HTTP body sends over a single long-polled connection) in OKHTTP3 that does not require data to be constantly flowing between the client and the server.
For context, I am trying to implement a system where there can be intermittent data pushes can occur from either the client or the server over a persistent connection. The application is data-use sensitive, so I don't want the client sending requests to the server to see if there is data ready, I just want the server to push it.
A Websocket connection is the ideal solution to your problem. This creates a persistent connection between the client and the server and both parties can start sending data at any time.
in OKHTTP you can implement this by
adding the library to your build gradle file compile 'com.squareup.okhttp3:okhttp:3.6.0'
Create a class that implements the okhttp WebsocketListener interface
private final class MyWebSocketListener extends WebSocketListener {
private static final int CLOSE_STATUS = 1000;
#Override
public void onOpen(WebSocket webSocket, Response response) {
webSocket.send("Hello");
webSocket.close(CLOSE_STATUS, "Goodbye");
}
#Override
public void onMessage(WebSocket webSocket, String text) {
log(text);
}
#Override
public void onMessage(WebSocket webSocket, ByteString bytes) {
log(bytes.hex());
}
#Override
public void onClosing(WebSocket webSocket, int code, String reason) {
webSocket.close(CLOSE_STATUS, null);
log("Closing");
}
#Override
public void onFailure(WebSocket webSocket, Throwable t, Response response) {
log(t.getMessage());
}
}
Create a method to initiate the connection
private void connect() {
Request request = new Request.Builder().url("ws://my.websocket.url").build();
MyWebSocketListener listener = new MyWebSocketListener();
WebSocket ws = client.newWebSocket(request, listener);
\\ to shutdown the connection client.dispatcher().executorService().shutdown();
}
This should establish a connection with the server and should persist as long as the application is alive. I recommend reading more on websockets if you are the same person responsible for the backend.
Related
I'm trying to implement an async server application using Avro IPC. As far as I've researched, it is possible to make client async calls by calling the method of generated Callback protocol classes like this:
My generated protocol class:
#org.apache.avro.specific.AvroGenerated
public interface TestProtocol {
public static final org.apache.avro.Protocol PROTOCOL = /*ommited*/;
ResponseTest send(MessageTest TestMsg);
#org.apache.avro.specific.AvroGenerated
public interface Callback extends TestProtocol {
public static final org.apache.avro.Protocol PROTOCOL = TestProtocol.PROTOCOL;
void send(MessageTest TestMsg, org.apache.avro.ipc.Callback<ResponseTest> callback) throws java.io.IOException;
}
}
And implementation of this code
public final class TestProtocolImplAsync implements TestProtocol.Callback {
#Override
public #NotNull ResponseTest send(#NotNull MessageTest TestMsg) {
return new ResponseTest("Sync call");
}
#Override
public void send(#NotNull MessageTest TestMsg,
#NotNull org.apache.avro.ipc.Callback<ResponseTest> callback) {
callback.handleResult(new ResponseTest("Async call"));
}
}
The implementation of TestProtocol is binded to TestProtocolImpl on server side. However, while calling it on client side this way:
SpecificRequestor.getClient(TestProtocol.Callback.class, client).send(new MessageTest(/*params*/), new Callback<ResponseTest>() {
#Override
public void handleResult(#NotNull ResponseTest result) {
System.out.println(result.toString());
}
#Override
public void handleError(#NotNull Throwable error) {
//whatever
}
})
I keep getting sync server method called. I haven't found any info about this in documentation, but am I right that callback method is only to be implemented on async client side, not server, and it is impossible to process request on server asyncrously this way and call callback method from server side? Or am I missing something in my server settings?
I want to achieve the following using spring-integration: having a singleton open socket that constantly receives and writes data, asyncrhon!
This means I have to open a socket that constantly reads from the single socket, dispatches each message for async processing, and return the responses over the socket also async.
How can I achieve that asynchron pattern?
Especially: how can I use Serializer/Deserializer? As far as I understood, a serializer is only invoked on a new socket connection, so in my case only once at start of the first message?
#Configuration
public class SocketConfig {
#Bean
public TcpConnectionFactoryFactoryBean tcpFactory(MyConverter converter) {
TcpConnectionFactoryFactoryBean fact = new TcpConnectionFactoryFactoryBean();
fact.setType("server");
fact.setPort(PORT);
fact.setUsingNio(true); //should I use true or false?
fact.setSingleUse(false); //keep socket constantly open
fact.setSerializer(converter);
fact.setDeserializer(converter);
return fact;
}
#Bean
public TcpInboundGateway serverGateway(
#Qualifier("tcpFactory") TcpConnectionFactoryFactoryBean factory,
#Qualifier("serverChannel") MessageChannel serverChannel) throws Exception {
TcpInboundGateway g = new TcpInboundGateway();
g.setConnectionFactory(factory.getObject());
g.setRequestChannel(serverChannel);
return g;
}
}
#MessageEndpoint
public class SocketEndpoint {
#ServiceActivator(inputChannel = "serverChannel")
public Object run(Object obj) {
}
}
#Service
public class MyConverter implements Serializer<Object>, Deserializer<Object> {
//read from socket
#Override
public Object deserialize(InputStream inputStream) {
}
//send back to socket
#Override
public void serialize(Object message, OutputStream outputStream) {
}
}
A gateway is used for individual request/response pairs.
If you need to send multiple responses for a single request, you must use collaborating channel adapters as described in the documentation.
Collaborating adapters can also be used (server-side or client-side) for totally asynchronous communication (rather than with request/reply semantics).
On the server side, care must be taken to populate the ip_connectionId header because it is used to correlate the message to a connection. Messages that originate at the inbound adapter will automatically have the header set. If you wish to construct other messages to send, you will need to set the header. The header value can be captured from an incoming message.
In the Spring WebSocket docs I found this sentence:
It is important to know that a server cannot send unsolicited messages.
http://docs.spring.io/spring/docs/current/spring-framework-reference/html/websocket.html
(25.4.1)
However I tried this code:
#Controller
public class WebsocketTest {
#Autowired
public SimpMessageSendingOperations messagingTemplate;
#PostConstruct
public void init(){
ScheduledExecutorService statusTimerExecutor=Executors.newSingleThreadScheduledExecutor();
statusTimerExecutor.scheduleAtFixedRate(new Runnable() {
#Override
public void run() {
messagingTemplate.convertAndSend("/topic/greetings", new Object());
}
}, 5000,5000, TimeUnit.MILLISECONDS);
}
}
And the message is broadcasted every 5000ms as expected.
So why Spring docs says that a server cannot send unsollicited messages?
The next sentence might mean that in the stomp.js client you are required to set a subscription:
All messages from a server must be in response to a specific client
subscription
But this does not necessarily mean in response to a request. For example a web socket could send information to the following:
Javascript:
stompClient.subscribe('/return/analyze', function(data) {
generateTableData(JSON.parse(data.body));
});
Spring:
#Autowired
private SimpMessagingTemplate simpMessagingTemplate;
public void sendSetpoint(String data) throws Exception {
this.simpMessagingTemplate.convertAndSend("/return/analyze", data);
}
But it cannot send unsolicited messages to the client unless that subscription exists. If this is their intended point it is a little poorly worded.
Note: see update at the bottom of the question for what I eventually concluded.
I need to send multiple responses to a request over the web socket that sent the request message, the first one quickly, and the others after the data is verified (somewhere between 10 and 60 seconds later, from multiple parallel threads).
I am having trouble getting the later responses to stop broadcasting over all open web sockets. How do I get them to only send to the initial web socket? Or should I use something besides Spring STOMP (because, to be honest, all I want is the message routing to various functions, I don't need or want the ability to broadcast to other web sockets, so I suspect I could write the message distributor myself, even though it is reinventing the wheel).
I am not using Spring Authentication (this is being retrofitted into legacy code).
On the initial return message, I can use #SendToUser, and even though we don't have a user, Spring only sends the return value to the websocket that sent the message. (see this question).
With the slower responses, though, I think I need to use SimpMessagingTemplate.convertAndSendToUser(user, destination, message), but I can't, because I have to pass in the user, and I can't figure out what user the #SendToUser used. I tried to follow the steps in this question, but didn't get it to work when not authenticated (principal.getName() returns null in this case).
I've simplified this considerably for the prototype, so don't worry about synchronizing threads or anything. I just want the web sockets to work correctly.
Here is my controller:
#Controller
public class TestSocketController
{
private SimpMessagingTemplate template;
#Autowired
public TestSocketController(SimpMessagingTemplate template)
{
this.template = template;
}
// This doesn't work because I need to pass something for the first parameter.
// If I just use convertAndSend, it broacasts the response to all browsers
void setResults(String ret)
{
template.convertAndSendToUser("", "/user/topic/testwsresponse", ret);
}
// this only sends "Testing Return" to the browser tab hooked to this websocket
#MessageMapping(value="/testws")
#SendToUser("/topic/testwsresponse")
public String handleTestWS(String msg) throws InterruptedException
{
(new Thread(new Later(this))).start();
return "Testing Return";
}
public class Later implements Runnable
{
TestSocketController Controller;
public Later(TestSocketController controller)
{
Controller = controller;
}
public void run()
{
try
{
java.lang.Thread.sleep(2000);
Controller.setResults("Testing Later Return");
}
catch (Exception e)
{
}
}
}
}
For the record, here is the browser side:
var client = null;
function sendMessage()
{
client.send('/app/testws', {}, 'Test');
}
// hooked to a button
function test()
{
if (client != null)
{
sendMessage();
return;
}
var socket = new SockJS('/application-name/sendws/');
client = Stomp.over(socket);
client.connect({}, function(frame)
{
client.subscribe('/user/topic/testwsresponse', function(message)
{
alert(message);
});
sendMessage();
});
});
And here is the config:
#Configuration
#EnableWebSocketMessageBroker
public class TestSocketConfig extends AbstractWebSocketMessageBrokerConfigurer
{
#Override
public void configureMessageBroker(MessageBrokerRegistry config)
{
config.setApplicationDestinationPrefixes("/app");
config.enableSimpleBroker("/queue", "/topic");
config.setUserDestinationPrefix("/user");
}
#Override
public void registerStompEndpoints(StompEndpointRegistry registry)
{
registry.addEndpoint("/sendws").withSockJS();
}
}
UPDATE: Due to the security issues involved with the possibility of information being sent over other websockets than the originating socket, I ended up recommending to my group that we do not use the Spring 4.0 implementation of STOMP over Web Sockets. I understand why the Spring team did it the way they did it, and it is more power then we needed, but the security restrictions on our project were severe enough, and the actual requirements were simple enough, that we decided to go a different way. That doesn't invalidate the answers below, so make your own decision based on your projects needs. At least we have hopefully all learned the limitations of the technology, for good or bad.
Why don't you use a separate topic for each client?
Client generates a session id.
var sessionId = Math.random().toString(36).substring(7);
Client subscribes to /topic/testwsresponse/{sessionId}, then sends a message to '/app/testws/{sessionId}'.
In your controller you use #MessageMapping(value="/testws/{sessionId}") and remove #SendToUser. You can use #DestinationVariable to access sessionId in your method.
The controller sends further responses to /topic/testwsresponse/{sessionId}.
Essentially Spring does a similar thing internally when you use user destinations. Since you don't use Spring Authentication you cannot rely on this mechanism but you can easily implement your own as I described above.
var client = null;
var sessionId = Math.random().toString(36).substring(7);
function sendMessage()
{
client.send('/app/testws/' + sessionId, {}, 'Test');
}
// hooked to a button
function test()
{
if (client != null)
{
sendMessage();
return;
}
var socket = new SockJS('/application-name/sendws/');
client = Stomp.over(socket);
client.connect({}, function(frame)
{
client.subscribe('/topic/testwsresponse/' + sessionId, function(message)
{
alert(message);
});
// Need to wait until subscription is complete
setTimeout(sendMessage, 1000);
});
});
Controller:
#Controller
public class TestSocketController
{
private SimpMessagingTemplate template;
#Autowired
public TestSocketController(SimpMessagingTemplate template)
{
this.template = template;
}
void setResults(String ret, String sessionId)
{
template.convertAndSend("/topic/testwsresponse/" + sessionId, ret);
}
#MessageMapping(value="/testws/{sessionId}")
public void handleTestWS(#DestinationVariable String sessionId, #Payload String msg) throws InterruptedException
{
(new Thread(new Later(this, sessionId))).start();
setResults("Testing Return", sessionId);
}
public class Later implements Runnable
{
TestSocketController Controller;
String sessionId;
public Later(TestSocketController controller, String sessionId)
{
Controller = controller;
this.sessionId = sessionId;
}
public void run()
{
try
{
java.lang.Thread.sleep(2000);
Controller.setResults("Testing Later Return", sessionId);
}
catch (Exception e)
{
}
}
}
}
Just tested it, works as expected.
This is not full answer. Just general consideration and suggestion.
You cannot do different stuff or type of connection via the same socket. Why not have different sockets for different work? Some with authentication and some without. Some for quick task and some for long execution.
I did a simple web socket communication with spring 4, STOMP and sock.js, following this https://spring.io/guides/gs/messaging-stomp-websocket/
Now I want to upgrade it to simple chat. My problem is that when user subscribes to new chat room, he should get past messages. I don't know how to capture the moment when he subscribed to send him the list of the messages.
I tried using #MessageMapping annotation, but didn't reach any success:
#Controller
public class WebSocketController {
#Autowired
private SimpMessagingTemplate messagingTemplate;
#MessageMapping("/chat/{chatId}")
public void chat(ChatMessage message, #DestinationVariable String chatId) {
messagingTemplate.convertAndSend("/chat/" + chatId, new ChatMessage("message: " + message.getText()));
}
#SubscribeMapping("/chat")
public void chatInit() {
System.out.println("worked");
int chatId = 1; //for example
messagingTemplate.convertAndSend("/chat/" + chatId, new ChatMessage("connected"));
}
}
Then I created that:
#Controller
public class ApplicationEventObserverController implements ApplicationListener<ApplicationEvent> {
#Override
public void onApplicationEvent(ApplicationEvent applicationEvent) {
System.out.println(applicationEvent);
}
}
It works, but captures all possible events, I don't think it is a good practice.
So, my question can be rephrased: how to send initial data when user subscried to sth?
You can return anything directly to a client when it subscribes to a destination using a #SubscribeMapping handler method. The returned object won't go to the broker but will be sent directly to the client:
#SubscribeMapping("/chat")
public Collection<ChatMessage> chatInit() {
...
return messages;
}
On the client side:
socket.subscribe("/app/chat", function(message) {
...
});
Check out the chat example on GitHub, which shows this exact scenario.