Use the Spring Initializer to generate a pain, java Spring Boot project without additional dependencies. Set the boot version to 2.7.x, the build to Maven and the packaging to Jar.

Add the spring-cloud-function-adapter-azure POM dependency:

<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-function-adapter-azure</artifactId>
	<version>3.2.9 or higher</version>
</dependency>

Having the adapter on the classpath activates the Azure Java Worker integration.

Implement the Azure Java Functions as @FunctionName annotated methods:

import java.util.Optional;
import java.util.function.Function;

import com.microsoft.azure.functions.ExecutionContext;
import com.microsoft.azure.functions.HttpMethod;
import com.microsoft.azure.functions.HttpRequestMessage;
import com.microsoft.azure.functions.annotation.AuthorizationLevel;
import com.microsoft.azure.functions.annotation.FunctionName;
import com.microsoft.azure.functions.annotation.HttpTrigger;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class MyAzureFunction {

	@Autowired
	private Function<String, String> uppercase;

	@FunctionName("ditest")
	public String execute(
			@HttpTrigger(name = "req", methods = { HttpMethod.GET,
					HttpMethod.POST }, authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Optional<String>> request,
			ExecutionContext context) {

		return this.uppercase.apply(request.getBody().get());
	}
}

The @FunctionName annotated methods represent the Azure Function implementations.
The class must be marked with the Spring @Component annotation.
You can use any Spring mechanism to auto-wire the Spring beans used for the function implementation.

Add the host.json configuration under the src/main/resources folder:

{
	"version": "2.0",
	"extensionBundle": {
		"id": "Microsoft.Azure.Functions.ExtensionBundle",
		"version": "[3.*, 4.0.0)"
	}
}

When bootstrapped as Spring Boot project make sure to either disable the spring-boot-maven-plugin plugin or cover it into thin-layout:

<plugin>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-maven-plugin</artifactId>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot.experimental</groupId>
			<artifactId>spring-boot-thin-layout</artifactId>
			<version>${spring-boot-thin-layout.version}</version>
		</dependency>
	</dependencies>
</plugin>

Since Azure Functions requires a specific, custom, Jar packaging we have to disable SpringBoot one.

Add the azure-functions-maven-plugin to your POM configuration. A sample configuration would look like this.

<plugin>
	<groupId>com.microsoft.azure</groupId>
	<artifactId>azure-functions-maven-plugin</artifactId>
	<version>1.22.0 or higher</version>

	<configuration>
		<appName>YOUR-AZURE-FUNCTION-APP-NAME</appName>
		<resourceGroup>YOUR-AZURE-FUNCTION-RESOURCE-GROUP</resourceGroup>
		<region>YOUR-AZURE-FUNCTION-APP-REGION</region>
		<appServicePlanName>YOUR-AZURE-FUNCTION-APP-SERVICE-PLANE-NAME</appServicePlanName>
		<pricingTier>YOUR-AZURE-FUNCTION-PRICING-TIER</pricingTier>

		<hostJson>${project.basedir}/src/main/resources/host.json</hostJson>

		<runtime>
			<os>linux</os> 
			<javaVersion>11</javaVersion>
		</runtime>

		<funcPort>7072</funcPort>

		<appSettings>
			<property>
				<name>FUNCTIONS_EXTENSION_VERSION</name>
				<value>~4</value>
			</property>
		</appSettings>
	</configuration>
	<executions>
		<execution>
			<id>package-functions</id>
			<goals>
				<goal>package</goal>
			</goals>
		</execution>
	</executions>
</plugin>

Set the AZURE subscription configuration such as app name, resource group, region, service plan, pricing Tier
Runtime configuration:
- Java Versions
- Specify Deployment OS

Build the project:
```
./mvnw clean package
```

Running Locally

NOTE: To run locally on top of Azure Functions, and to deploy to your live Azure environment, you will need Azure Functions Core Tools installed along with the Azure CLI (see here). For some configuration you would need the Azurite emulator as well.

Then build and run the sample:

./mvnw clean package
./mvnw azure-functions:run

Running on Azure

Make sure you are logged in your Azure account.

az login

Build and deploy

./mvnw clean package
./mvnw azure-functions:deploy

Debug locally

Run the function in debug mode.

./mvnw azure-functions:deploy -DenableDebug

Alternatively and the JAVA_OPTS value to your local.settings.json like this:

{
	"IsEncrypted": false,
	"Values": {
		...
		"FUNCTIONS_WORKER_RUNTIME": "java",
		"JAVA_OPTS": "-Djava.net.preferIPv4Stack=true -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=127.0.0.1:5005"
	}
}

VS Code remote debug configuration:

```json
{
	"version": "0.2.0",
	"configurations": [
		{
			"type": "java",
			"name": "Attach to Remote Program",
			"request": "attach",
			"hostName": "localhost",
			"port": "5005"
		},  
}
	
```