Serverless Java Apps with VS Code

Serverless, as indicated by its name, allows you to execute your code in an environment without having to first create a VM or publish a web application.

This tutorial guides you through creating a serverless function project with VS Code and the Azure Functions extension. You be able to test it locally and deploy it to Azure Functions. When you're done, you'll have a HTTP-triggered function app running in Azure.

Prerequisites

To develop Functions apps with Java, you must have the following installed:

• Java Developer Kit, version 1.8.
• Apache Maven, version 3.0 or above.

Important: The JAVA_HOME environment variable must be set to the install location of the JDK to complete this tutorial.

Install the Azure Functions extension

Azure Functions extension provides an easy way for you to manage your serverless functions with Azure. It supports both Java and JavaScript Functions with features including:

• Create new project.
• Create new Function from template.
• Debug Function projects locally.
• View Azure Function Apps.
• Create, delete, start, stop and restart Azure Function Apps.
• JSON Intellisense for function.json, host.json and proxies.json files.

In this tutorial, we will leverage this extension to create the serverless function. For a more command line Maven-centric experience, you can also check out the Maven Functions Tutorial. The Java support of this extension leverages a lot from our Maven Plugin for Azure Functions.

To install the Functions extension, open the Extension view by pressing ⇧⌘X (Windows, Linux Ctrl+Shift+X) and search for azure functions to filter the results. Select the Azure Functions extension.

Generate a new Functions project

Once you've installed the Azure Functions extension, you can easily create a new project by:

1. Click Create New Project button on the AZURE FUNCTIONS Explorer view.
2. Select target folder.
3. Select Java the target language.
4. Fill in the parameters.

The extension will leverage Maven archetype to create the function project in the folder you specified.

Within the created project, there's a simple HTTP triggered 'Hello World' Function which reads the input from HTTP query string or body and returns it back immediately.

/**
 * Azure Functions with HTTP Trigger.
 */
public class Function {
    @FunctionName("hello")
    public HttpResponseMessage<String> httpHandler(
            @HttpTrigger(name = "req", methods = {"get", "post"}, authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Optional<String>> request,
            final ExecutionContext context
    ) {
        context.getLogger().info("Java HTTP trigger processed a request.");

        String query = request.getQueryParameters().get("name");
        String name = request.getBody().orElse(query);

        if (name == null) {
            return request.createResponse(400, "Please pass a name on the query string or in the request body");
        } else {
            return request.createResponse(200, "Hello, " + name);
        }
    }
}

Install the Azure Functions Core Tools

Note: This step is optional and only required to locally run and debug your Java Functions source code.

The Azure Functions Core Tools 2.0 provides a local development environment for writing, running, and debugging Azure Functions. The installation package for v2 is a self-contained cross-platform package

Windows

npm i -g azure-functions-core-tools@core --unsafe-perm true

macOS

Homebew:

brew tap azure/functions
brew install azure-functions-core-tools

Linux

Ubuntu/Debian

1. Register the Microsoft Product key as trusted.

curl https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor > microsoft.gpg
sudo mv microsoft.gpg /etc/apt/trusted.gpg.d/microsoft.gpg

2. Add source

Ubuntu 16.04 / Linux Mint 18

sudo sh -c 'echo "deb [arch=amd64] https://packages.microsoft.com/repos/microsoft-ubuntu-xenial-prod xenial main" > /etc/apt/sources.list.d/dotnetdev.list'
sudo apt-get update

3. Install

sudo apt install azure-functions-core-tools

Code and test Azure Functions locally

NOTE: npm can be used on all platforms. On Unix platforms, you may need to specify --unsafe-perm if you are running npm with sudo. This is necessary due to npm's post install script behavior.

NOTE: If you're running the v2 on Windows, Linux, or macOS, make sure to enable the beta runtime in function app settings, otherwise you may not see the same results as running locally.

Run and debug the function locally

Once the function is created, press F5 to start the function. Behind the scene, we've configured the launch.json debugger configuration file to build the functions project and then start the local runtime provided by Azure Functions Core Tools 2.0. If you would like to debug your function, set a break point and then send a request to trigger the HTTP function.

curl -w '\n' -d LocalFunction http://localhost:7071/api/hello

You should see:

Hello LocalFunction!

Use Ctrl+C in the terminal to stop the function code.

Deploy the function to Azure

If you don't have an Azure subscription, you can sign up for a free Azure account.

Create your free Azure account

The deploy process leverages the Azure Account extension (installed along with the Azure Functions extension as an dependency) and you would need to sign in with your Azure subscription. If you do not have an Azure subscription, sign up today for a free 30 day account and get $200 in Azure Credits to try out any combination of Azure services.

To log into Azure, run Azure: Sign In from the Command Palette (⇧⌘P (Windows, Linux Ctrl+Shift+P)). You can then sign into your account using the Device Login flow. Click on Copy & Open to open your default browser.

Paste in the access code and continue the sign in process.

After signing in, you can click Deploy to Function App button, select the folder of the project you would like to deploy from, and follow the prompt hint to configure your function project.

Once the deploy is completed, test the function app running on Azure using curl:

curl -w '\n' https://fabrikam-function-20170920120101928.azurewebsites.net/api/hello -d AzureFunctions

You should see:

Hello AzureFunctions!

Add additional functions to the project

The extension also supports adding new functions to the existing project. You only need to:

1. Click Add Function button on the AZURE FUNCTIONS Explorer bar.
2. Select project folder.
3. Select function type.
4. Fill in the parameters for this function type.

Remote debug functions running in the cloud

Although the local core tool from Azure Functions is running the same code as in the cloud, sometimes environment differences may cause your function to behave differently. With remote debugging, can troubleshoot those issues.

We've released a special Remote Debugging Tool to help you set up the remote debugging session. You can easily install it via npm:

npm install -g cloud-debug-tools

Once it's installed, run the tool to attach to the running Function on Azure

dbgproxy fabrikam-function-20170920120101928.azurewebsites.net

The tool depends on Azure CLI to fetch your credential so make sure you've logged in with the same account.

az login

The tool will then figure out the rest for you. Once it's connected to the running Functions, add a new debugging configuration to attach to the local port opened by it.

{
    "name": "Attach to Azure Functions on Cloud",
    "type": "java",
    "request": "attach",
    "hostName": "localhost",
    "port": 8898
}

Now you can set a break point and attach to your cloud function using VS Code. When you launch a debug session with the above configuration, you can step through it just like you did locally. It's also useful if you don't have .Net Core and the Azure Functions CLI core tool installed on your local environment and you want to jump start within the cloud directly.

Next steps

You have created a Java function app with a simple HTTP trigger and deployed it to Azure Functions.

• Review the Java Functions developer guide for more information on developing Java functions.
• To learn more about Java Debugging features, see Java Debugging Tutorial