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--- title: Use Java to create a chat room with Azure Functions and SignalR Service description: A quickstart for using Azure SignalR Service and Azure Functions to create an App showing GitHub star count using Java. author: vicancy ms.author: lianwei ms.date: 04/04/2022 ms.topic: quickstart ms.service: azure-signalr-service ms.devlang: java ms.custom: devx-track-java, mode-api, devx-track-extended-java --- # Quickstart: Use Java to create an App showing GitHub star count with Azure Functions and SignalR Service In this article, you'll use Azure SignalR Service, Azure Functions, and Java to build a serverless application to broadcast messages to clients. > [!NOTE] > The code in this article is available on [GitHub](https://github.com/aspnet/AzureSignalR-samples/tree/main/samples/QuickStartServerless/java). [!INCLUDE [Connection string security](includes/signalr-connection-string-security.md)] ## Prerequisites - A code editor, such as [Visual Studio Code](https://code.visualstudio.com/) - An Azure account with an active subscription. If you don't already have an account, [create an account for free](https://azure.microsoft.com/pricing/purchase-options/azure-account?cid=msft_learn). - [Azure Functions Core Tools](https://github.com/Azure/azure-functions-core-tools#installing). Used to run Azure Function apps locally. - The required SignalR Service bindings in Java are only supported in Azure Function Core Tools version 2.4.419 (host version 2.0.12332) or above. - To install extensions, Azure Functions Core Tools requires the [.NET Core SDK](https://dotnet.microsoft.com/download) installed. However, no knowledge of .NET is required to build Java Azure Function apps. - [Java Developer Kit](https://www.azul.com/downloads/zulu/), version 11 - [Apache Maven](https://maven.apache.org), version 3.0 or above. This quickstart can be run on macOS, Windows, or Linux. ## Create an Azure SignalR Service instance [!INCLUDE [Create instance](includes/signalr-quickstart-create-instance.md)] ## Configure and run the Azure Function app Make sure you have Azure Function Core Tools, Java (version 11 in the sample), and Maven installed. 1. Initialize the project using Maven: ```bash mvn archetype:generate -DarchetypeGroupId=com.microsoft.azure -DarchetypeArtifactId=azure-functions-archetype -DjavaVersion=11 ``` Maven asks you for values needed to finish generating the project. Provide the following values: | Prompt | Value | Description | | ------ | ----- | ----------- | | **groupId** | `com.signalr` | A value that uniquely identifies your project across all projects, following the [package naming rules](https://docs.oracle.com/javase/specs/jls/se6/html/packages.html#7.7) for Java. | | **artifactId** | `java` | A value that is the name of the jar, without a version number. | | **version** | `1.0-SNAPSHOT` | Choose the default value. | | **package** | `com.signalr` | A value that is the Java package for the generated function code. Use the default. | 1. Go to the folder `src/main/java/com/signalr` and copy the following code to *Function.java*: ```java package com.signalr; import com.google.gson.Gson; import com.microsoft.azure.functions.ExecutionContext; import com.microsoft.azure.functions.HttpMethod; import com.microsoft.azure.functions.HttpRequestMessage; import com.microsoft.azure.functions.HttpResponseMessage; import com.microsoft.azure.functions.HttpStatus; import com.microsoft.azure.functions.annotation.AuthorizationLevel; import com.microsoft.azure.functions.annotation.FunctionName; import com.microsoft.azure.functions.annotation.HttpTrigger; import com.microsoft.azure.functions.annotation.TimerTrigger; import com.microsoft.azure.functions.signalr.*; import com.microsoft.azure.functions.signalr.annotation.*; import org.apache.commons.io.IOUtils; import java.io.IOException; import java.io.InputStream; import java.net.URI; import java.net.http.HttpClient; import java.net.http.HttpRequest; import java.net.http.HttpResponse; import java.net.http.HttpResponse.BodyHandlers; import java.nio.charset.StandardCharsets; import java.util.Optional; public class Function { private static String Etag = ""; private static String StarCount; @FunctionName("index") public HttpResponseMessage run( @HttpTrigger( name = "req", methods = {HttpMethod.GET}, authLevel = AuthorizationLevel.ANONYMOUS)HttpRequestMessage<Optional<String>> request, final ExecutionContext context) throws IOException { InputStream inputStream = getClass().getClassLoader().getResourceAsStream("content/index.html"); String text = IOUtils.toString(inputStream, StandardCharsets.UTF_8.name()); return request.createResponseBuilder(HttpStatus.OK).header("Content-Type", "text/html").body(text).build(); } @FunctionName("negotiate") public SignalRConnectionInfo negotiate( @HttpTrigger( name = "req", methods = { HttpMethod.POST }, authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Optional<String>> req, @SignalRConnectionInfoInput( name = "connectionInfo", hubName = "serverless") SignalRConnectionInfo connectionInfo) { return connectionInfo; } @FunctionName("broadcast") @SignalROutput(name = "$return", hubName = "serverless") public SignalRMessage broadcast( @TimerTrigger(name = "timeTrigger", schedule = "*/5 * * * * *") String timerInfo) throws IOException, InterruptedException { HttpClient client = HttpClient.newHttpClient(); HttpRequest req = HttpRequest.newBuilder().uri(URI.create("https://api.github.com/repos/azure/azure-signalr")).header("User-Agent", "serverless").header("If-None-Match", Etag).build(); HttpResponse<String> res = client.send(req, BodyHandlers.ofString()); if (res.headers().firstValue("Etag").isPresent()) { Etag = res.headers().firstValue("Etag").get(); } if (res.statusCode() == 200) { Gson gson = new Gson(); GitResult result = gson.fromJson(res.body(), GitResult.class); StarCount = result.stargazers_count; } return new SignalRMessage("newMessage", "Current start count of https://github.com/Azure/azure-signalr is:".concat(StarCount)); } class GitResult { public String stargazers_count; } } ``` 1. Some dependencies need to be added. Open *pom.xml* and add the following dependencies used in the code: ```xml <dependency> <groupId>com.microsoft.azure.functions</groupId> <artifactId>azure-functions-java-library-signalr</artifactId> <version>1.0.0</version> </dependency> <dependency> <groupId>commons-io</groupId> <artifactId>commons-io</artifactId> <version>2.4</version> </dependency> <dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.8.7</version> </dependency> ``` 1. The client interface for this sample is a web page. We read HTML content from *content/index.html* in the `index` function, and then create a new file *content/index.html* in the `resources` directory. Your directory tree should look like this: ``` nsProject | - src | | - main | | | - java | | | | - com | | | | | - signalr | | | | | | - Function.java | | | - resources | | | | - content | | | | | - index.html | - pom.xml | - host.json | - local.settings.json ``` 1. Open *index.html* and copy the following content: ```html <html> <body> <h1>Azure SignalR Serverless Sample</h1> <div id="messages"></div> <script src="https://cdnjs.cloudflare.com/ajax/libs/microsoft-signalr/3.1.7/signalr.min.js"></script> <script> let messages = document.querySelector('#messages'); const apiBaseUrl = window.location.origin; const connection = new signalR.HubConnectionBuilder() .withUrl(apiBaseUrl + '/api') .configureLogging(signalR.LogLevel.Information) .build(); connection.on('newMessage', (message) => { document.getElementById("messages").innerHTML = message; }); connection.start() .catch(console.error); </script> </body> </html> ``` 1. Azure Functions requires a storage account to work. You can install and run the [Azure Storage Emulator](../storage/common/storage-use-azurite.md). 1. You're almost done now. The last step is to set a connection string of the SignalR Service to Azure Function settings. 1. Search for the Azure SignalR instance you deployed earlier using the **Search** box in Azure portal. Select the instance to open it.  1. Select **Keys** to view the connection strings for the SignalR Service instance.  1. Copy the primary connection string, and then run the following command. [!INCLUDE [Connection string security comment](includes/signalr-connection-string-security-comment.md)] ```bash func settings add AzureSignalRConnectionString "<signalr-connection-string>" # Also we need to set AzureWebJobsStorage as Azure Function's requirement func settings add AzureWebJobsStorage "UseDevelopmentStorage=true" ``` 1. Run the Azure Function in local: ```bash mvn clean package mvn azure-functions:run ``` After Azure Function is running locally, go to `http://localhost:7071/api/index` and you'll see the current star count. If you star or "unstar" in the GitHub, you'll get a star count refreshing every few seconds. [!INCLUDE [Cleanup](includes/signalr-quickstart-cleanup.md)] Having issues? Try the [troubleshooting guide](signalr-howto-troubleshoot-guide.md) or [let us know](https://aka.ms/asrs/qsjava). ## Next steps In this quickstart, you built and ran a real-time serverless application in the local host. Next, learn more about how to bi-directional communicating between clients and Azure Function with SignalR Service. > [!div class="nextstepaction"] > [SignalR Service bindings for Azure Functions](../azure-functions/functions-bindings-signalr-service.md) > [!div class="nextstepaction"] > [Bi-directional communicating in Serverless](https://github.com/aspnet/AzureSignalR-samples/tree/main/samples/BidirectionChat) > [!div class="nextstepaction"] > [Create your first function with Java and Maven](../azure-functions/how-to-create-function-azure-cli.md?pivots=programming-language-java)