Fix Java Client transport select (#8143)

src/SignalR/clients/java/signalr/src/main/java/com/microsoft/signalr/HubConnection.java

@@ -93,6 +93,14 @@ public class HubConnection {
         this.tickRate = tickRateInMilliseconds;
     }
 
+    TransportEnum getTransportEnum() {
+        return this.transportEnum;
+    }
+
+    Transport getTransport() {
+        return transport;
+    }
+
     HubConnection(String url, Transport transport, boolean skipNegotiate, HttpClient httpClient,
                   Single<String> accessTokenProvider, long handshakeResponseTimeout, Map<String, String> headers, TransportEnum transportEnum) {
         if (url == null || url.isEmpty()) {
@@ -235,7 +243,8 @@ public class HubConnection {
 
         return httpClient.post(Negotiate.resolveNegotiateUrl(url), request).map((response) -> {
             if (response.getStatusCode() != 200) {
-                throw new RuntimeException(String.format("Unexpected status code returned from negotiate: %d %s.", response.getStatusCode(), response.getStatusText()));
+                throw new RuntimeException(String.format("Unexpected status code returned from negotiate: %d %s.",
+                        response.getStatusCode(), response.getStatusText()));
             }
             NegotiateResponse negotiateResponse = new NegotiateResponse(response.getContent());
 
@@ -377,8 +386,15 @@ public class HubConnection {
 
             if (response.getRedirectUrl() == null) {
                 Set<String> transports = response.getAvailableTransports();
-                if ((this.transportEnum == TransportEnum.ALL && !(transports.contains("WebSockets") || transports.contains("LongPolling"))) ||
+                if (this.transportEnum == TransportEnum.ALL) {
-                        (this.transportEnum == TransportEnum.WEBSOCKETS && !transports.contains("WebSockets")) ||
+                    if (transports.contains("WebSockets")) {
+                        this.transportEnum = TransportEnum.WEBSOCKETS;
+                    } else if (transports.contains("LongPolling")) {
+                        this.transportEnum = TransportEnum.LONG_POLLING;
+                    } else {
+                        throw new RuntimeException("There were no compatible transports on the server.");
+                    }
+                } else if (this.transportEnum == TransportEnum.WEBSOCKETS && !transports.contains("WebSockets") ||
                         (this.transportEnum == TransportEnum.LONG_POLLING && !transports.contains("LongPolling"))) {
                     throw new RuntimeException("There were no compatible transports on the server.");
                 }

src/SignalR/clients/java/signalr/src/test/java/com/microsoft/signalr/HubConnectionTest.java

@@ -11,8 +11,10 @@ import java.util.concurrent.CancellationException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 
+import io.reactivex.subjects.CompletableSubject;
 import org.junit.jupiter.api.Test;
 
 import io.reactivex.Observable;
@@ -1219,6 +1221,74 @@ class HubConnectionTest {
         assertEquals("{\"protocol\":\"json\",\"version\":1}" + RECORD_SEPARATOR, sentMessages[0]);
     }
 
+    @Test
+    public void TransportAllUsesLongPollingWhenServerOnlySupportLongPolling() {
+        AtomicInteger requestCount = new AtomicInteger(0);
+        TestHttpClient client = new TestHttpClient().on("POST",
+                (req) -> Single.just(new HttpResponse(200, "",
+                        "{\"connectionId\":\"bVOiRPG8-6YiJ6d7ZcTOVQ\",\""
+                                + "availableTransports\":[{\"transport\":\"LongPolling\",\"transferFormats\":[\"Text\",\"Binary\"]}]}")))
+                .on("GET", (req) -> {
+                    if (requestCount.get() == 0) {
+                        requestCount.incrementAndGet();
+                        return Single.just(new HttpResponse(200, "", ""));
+                    }
+                    return Single.just(new HttpResponse(204, "", ""));
+                });
+
+        HubConnection hubConnection = HubConnectionBuilder
+                .create("http://example.com")
+                .withTransport(TransportEnum.ALL)
+                .withHttpClient(client)
+                .build();
+
+        hubConnection.start().timeout(1, TimeUnit.SECONDS).blockingAwait();
+        assertTrue(hubConnection.getTransport() instanceof LongPollingTransport);
+        hubConnection.stop().timeout(1, TimeUnit.SECONDS).blockingAwait();
+    }
+
+    @Test
+    public void ClientThatSelectsWebsocketsThrowsWhenWebsocketsAreNotAvailable() {
+        TestHttpClient client = new TestHttpClient().on("POST",
+                (req) -> Single.just(new HttpResponse(200, "",
+                        "{\"connectionId\":\"bVOiRPG8-6YiJ6d7ZcTOVQ\",\""
+                                + "availableTransports\":[{\"transport\":\"LongPolling\",\"transferFormats\":[\"Text\",\"Binary\"]}]}")))
+                .on("GET", (req) -> {
+                    return Single.just(new HttpResponse(204, "", ""));
+                });
+
+        HubConnection hubConnection = HubConnectionBuilder
+                .create("http://example.com")
+                .withTransport(TransportEnum.WEBSOCKETS)
+                .withHttpClient(client)
+                .build();
+
+        assertEquals(TransportEnum.WEBSOCKETS, hubConnection.getTransportEnum());
+        RuntimeException exception = assertThrows(RuntimeException.class,
+                () -> hubConnection.start().timeout(1, TimeUnit.SECONDS).blockingAwait());
+
+        assertEquals(exception.getMessage(), "There were no compatible transports on the server.");
+    }
+
+    @Test
+    public void ClientThatSelectsLongPollingThrowsWhenLongPollingIsNotAvailable() {
+        TestHttpClient client = new TestHttpClient().on("POST",
+                (req) -> Single.just(new HttpResponse(200, "", "{\"connectionId\":\"bVOiRPG8-6YiJ6d7ZcTOVQ\",\""
+                        + "availableTransports\":[{\"transport\":\"WebSockets\",\"transferFormats\":[\"Text\",\"Binary\"]}]}")));
+
+        HubConnection hubConnection = HubConnectionBuilder
+                .create("http://example.com")
+                .withTransport(TransportEnum.LONG_POLLING)
+                .withHttpClient(client)
+                .build();
+
+        assertEquals(TransportEnum.LONG_POLLING, hubConnection.getTransportEnum());
+        RuntimeException exception = assertThrows(RuntimeException.class,
+                () -> hubConnection.start().timeout(1, TimeUnit.SECONDS).blockingAwait());
+
+        assertEquals(exception.getMessage(), "There were no compatible transports on the server.");
+    }
+
     @Test
     public void receivingServerSentEventsTransportFromNegotiateFails() {
         TestHttpClient client = new TestHttpClient().on("POST", "http://example.com/negotiate",