Add docs for MessagePack

aspnetcore/signalr/client-features.md

@@ -40,7 +40,7 @@ The table below shows the features and support for the clients that offer real-t
 | Server-Sent Events Transport |2.1.0|1.0.0|1.0.0|❌|
 | Long Polling Transport |2.1.0|1.0.0|1.0.0|3.0.0|
 | JSON Hub Protocol |2.1.0|1.0.0|1.0.0|1.0.0|
-| MessagePack Hub Protocol |2.1.0|1.0.0|1.0.0|❌|
+| MessagePack Hub Protocol |2.1.0|1.0.0|1.0.0|5.0.0|
 
 Support for enabling additional client features is tracked in [our issue tracker](https://github.com/dotnet/AspNetCore/issues).
 

aspnetcore/signalr/java-client.md

@@ -91,12 +91,43 @@ HubConnection hubConnection = HubConnectionBuilder.create("YOUR HUB URL HERE")
     })).build();
 ```
 
+::: moniker range=">= aspnetcore-5.0"
+
+### Passing Class information in Java
+
+When calling the `on`, `invoke`, or `stream` methods of `HubConnection` in the Java client, users should pass a `Type` object rather than a `Class<?>` object to describe any generic `Object` passed to the method. A `Type` can be acquired using the provided `TypeReference` class. For example, using a custom generic class named `Foo<T>`, the following code gets the `Type`:
+
+```java
+Type fooType = new TypeReference<Foo<String>>() { }).getType();
+```
+
+For non-generics, such as primitives or other non-parameterized types like `String`, you can simply use the built-in `.class`.
+
+When calling one of these methods with one or more object types, use the generics syntax when invoking the method. For example, when registering an `on` handler for a method named `func`, which takes as arguments a String and a `Foo<String>` object, use the following code to set an action to print the arguments:
+
+```java
+hubConnection.<String, Foo<String>>on("func", (param1, param2) ->{
+    System.out.println(param1);
+    System.out.println(param2);
+}, String.class, fooType);
+```
+
+This convention is necessary because we can not retrieve complete information about complex types with the `Object.getClass` method due to type erasure in Java. For example, calling `getClass` on an `ArrayList<String>` would not return `Class<ArrayList<String>>`, but rather `Class<ArrayList>`, which does not give the deserializer enough information to correctly deserialize an incoming message. The same is true for custom objects.
+
+::: moniker-end
+
 ## Known limitations
 
-::: moniker range=">= aspnetcore-3.0"
+::: moniker range=">= aspnetcore-5.0"
+
+* Transport fallback and the Server Sent Events transport aren't supported.
+
+::: moniker-end
+
+::: moniker range=">= aspnetcore-3.0 < aspnetcore-5.0"
 
-* Only the JSON protocol is supported.
 * Transport fallback and the Server Sent Events transport aren't supported.
+* Only the JSON protocol is supported.
 
 ::: moniker-end
 

aspnetcore/signalr/java-client/sample/pom.xml

@@ -28,6 +28,13 @@
             <version>1.0.0</version>
         </dependency>
         <!-- </snippet_dependencyElement> -->
+        <!-- <snippet_dependencyElement_messagePack> -->
+        <dependency>
+            <groupId>com.microsoft.signalr.messagepack</groupId>
+            <artifactId>signalr</artifactId>
+            <version>5.0.0</version>
+        </dependency>
+        <!-- </snippet_dependencyElement_messagePack> -->
     </dependencies>
 
 </project>

aspnetcore/signalr/messagepackhubprotocol.md

@@ -104,6 +104,26 @@ const connection = new signalR.HubConnectionBuilder()
 > [!NOTE]
 > At this time, there are no configuration options for the MessagePack protocol on the JavaScript client.
 
+### Java client
+
+To enable MessagePack with Java, install the `com.microsoft.signalr.messagepack` package. When using Gradle, add the following line to the `dependencies` section of the *build.gradle* file:
+
+```gradle
+implementation 'com.microsoft.signalr.messagepack:signalr-messagepack:5.0.0'
+```
+
+When using Maven, add the following lines inside the `<dependencies>` element of the *pom.xml* file:
+
+[!code-xml[pom.xml dependency element messagePack](java-client/sample/pom.xml?name=snippet_dependencyElement_messagePack)]
+
+Call `withHubProtocol(new MessagePackHubProtocol())` on `HubConnectionBuilder`.
+
+```java
+HubConnection messagePackConnection = HubConnectionBuilder.create("YOUR HUB URL HERE")
+    .withHubProtocol(new MessagePackHubProtocol())
+    .build();
+```
+
 ## MessagePack quirks
 
 There are a few issues to be aware of when using the MessagePack Hub Protocol.
@@ -172,6 +192,10 @@ InvalidDataException: Error binding arguments. Make sure that the types of the p
 
 For more information on this limitation, see GitHub issue [aspnet/SignalR#2937](https://github.com/aspnet/SignalR/issues/2937).
 
+### Chars and Strings in Java
+
+In the java client, `char` objects will be serialized as one-character `String` objects. This is in contrast with the C# and JavaScript client, which serialize them as `short` objects. The MessagePack spec itself does not define behavior for `char` objects, so it is up to the library author to determine how to serialize them. The difference in behavior between our clients is a result of the libraries we used for our implementations.
+
 ## Related resources
 
 * [Get Started](xref:tutorials/signalr)