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Edit the files in the src/main/asciidoc/ directory instead.
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This project provides an adapter layer for a Spring Cloud Function application onto Azure.
You can write an app with a single `@Bean` of type `Function` and it will be deployable in Azure if you get the JAR file laid out right.
This project provides an adapter layer for a Spring Cloud Function application onto Azure.
You can write an app with a single `@Bean` of type `Function` and it will be deployable in Azure if you get the JAR file laid out right.
There is an `AzureSpringBootRequestHandler` which you must extend, and provide the input and output types as annotated method parameters (enabling Azure to inspect the class and create JSON bindings). The base class has two useful methods (`handleRequest` and `handleOutput`) to which you can delegate the actual function call, so mostly the function will only ever have one line.
Example:
```java
public class FooHandler extends AzureSpringBootRequestHandler<Foo, Bar> {
@FunctionName("uppercase")
public Bar execute(
@HttpTrigger(name = "req", methods = { HttpMethod.GET,
HttpMethod.POST }, authLevel = AuthorizationLevel.ANONYMOUS)
Foo foo,
ExecutionContext context) {
return handleRequest(foo, context);
}
}
```
This Azure handler will delegate to a `Function<Foo,Bar>` bean (or a `Function<Publisher<Foo>,Publisher<Bar>>`). Some Azure triggers (e.g. `@CosmosDBTrigger`) result in a input type of `List` and in that case you can bind to `List` in the Azure handler, or `String` (the raw JSON). The `List` input delegates to a `Function` with input type `Map<String,Object>`, or `Publisher` or `List` of the same type. The output of the `Function` can be a `List` (one-for-one) or a single value (aggregation), and the output binding in the Azure declaration should match.
If your app has more than one `@Bean` of type `Function` etc. then you can choose the one to use by configuring `function.name`. Or if you make the `@FunctionName` in the Azure handler method match the function name it should work that way (also for function apps with multiple functions). The functions are extracted from the Spring Cloud `FunctionCatalog` so the default function names are the same as the bean names.
=== Accessing Azure ExecutionContext
Some time there is a need to access the target execution context provided by Azure runtime in the form of `com.microsoft.azure.functions.ExecutionContext`.
For example one of such needs is logging, so it can appear in the Azure console.
For that purpose Spring Cloud Function will register `ExecutionContext` as bean in the Application context, so it could be injected into your function.
For example
```java
@Bean
public Function<Foo, Bar> uppercase(ExecutionContext targetContext) {
return foo -> {
targetContext.getLogger().info("Invoking 'uppercase' on " + foo.getValue());
return new Bar(foo.getValue().toUpperCase());
};
}
```
Normally type-based injection should suffice, however if need to you can also utilise the bean name under which it is registered which is `targetExecutionContext`.
=== Notes on JAR Layout
You don't need the Spring Cloud Function Web at runtime in Azure, so you can exclude this before you create the JAR you deploy to Azure, but it won't be used if you include it so it doesn't hurt to leave it in. A function application on Azure is an archive generated by the Maven plugin. The function lives in the JAR file generated by this project. The sample creates it as an executable jar, using the thin layout, so that Azure can find the handler classes. If you prefer you can just use a regular flat JAR file. The dependencies should *not* be included.
== Build
----
./mvnw -U clean package
----
== Running the sample
You can run the sample locally, just like the other Spring Cloud Function samples:
---
./mvnw spring-boot:run
---
and `curl -H "Content-Type: text/plain" localhost:8080/function -d '{"value": "hello foobar"}'`.
You will need the `az` CLI app (see https://docs.microsoft.com/en-us/azure/azure-functions/functions-create-first-java-maven for more detail). To deploy the function on Azure runtime:
----
$ az login
$ mvn azure-functions:deploy
----
On another terminal try this: `curl https://<azure-function-url-from-the-log>/api/uppercase -d '{"value": "hello foobar!"}'`. Please ensure that you use the right URL for the function above. Alternatively you can test the function in the Azure Dashboard UI (click on the function name, go to the right hand side and click "Test" and to the bottom right, "Run").
The input type for the function in the Azure sample is a Foo with a single property called "value". So you need this to test it with something like below:
----
{
"value": "foobar"
}
----
NOTE: The Azure sample app is written in the "non-functional" style (using `@Bean`). The functional style (with just `Function` or `ApplicationContextInitializer`) is much faster on startup in Azure than the traditional `@Bean` style, so if you don't need `@Beans` (or `@EnableAutoConfiguration`) it's a good choice. Warm starts are not affected.
== Sample Function
Go to the link:../../spring-cloud-function-samples/function-sample-azure/[function-sample-azure] to learn about how the sample works, and how to run and test it.
