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Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:

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Once the early-adopter seats are all used, the price will go up and stay at $33/year.

Partner – Microsoft – NPI EA (cat = Baeldung)
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Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.

Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.

To learn more about Java features on Azure Container Apps, visit the documentation page.

You can also ask questions and leave feedback on the Azure Container Apps GitHub page.

Partner – Microsoft – NPI EA (cat= Spring Boot)
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Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.

Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.

To learn more about Java features on Azure Container Apps, you can get started over on the documentation page.

And, you can also ask questions and leave feedback on the Azure Container Apps GitHub page.

Partner – Orkes – NPI EA (cat=Spring)
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.

Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.

With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.

Try a 14-Day Free Trial of Orkes Conductor today.

Partner – Orkes – NPI EA (tag=Microservices)
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.

Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.

With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.

Try a 14-Day Free Trial of Orkes Conductor today.

eBook – Guide Spring Cloud – NPI EA (cat=Spring Cloud)
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eBook – Mockito – NPI EA (tag = Mockito)
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Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.

Get started with mocking and improve your application tests using our Mockito guide:

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eBook – Java Concurrency – NPI EA (cat=Java Concurrency)
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Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.

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eBook – Reactive – NPI EA (cat=Reactive)
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Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:

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eBook – Java Streams – NPI EA (cat=Java Streams)
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Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.

But these can also be overused and fall into some common pitfalls.

To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:

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eBook – Jackson – NPI EA (cat=Jackson)
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Do JSON right with Jackson

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Building a REST API with Spring?

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Course – LS – NPI EA (cat=Jackson)
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Get started with Spring and Spring Boot, through the Learn Spring course:

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Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:

>> The New “REST With Spring Boot”

Course – LSS – NPI EA (cat=Spring Security)
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Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.

I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.

You can explore the course here:

>> Learn Spring Security

Course – All Access – NPI EA (cat= Spring)
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All Access is finally out, with all of my Spring courses. Learn JUnit is out as well, and Learn Maven is coming fast. And, of course, quite a bit more affordable. Finally.

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Course – LSD – NPI EA (tag=Spring Data JPA)
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Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.

Get started with Spring Data JPA through the guided reference course:

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Partner – LambdaTest – NPI EA (cat=Testing)
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End-to-end testing is a very useful method to make sure that your application works as intended. This highlights issues in the overall functionality of the software, that the unit and integration test stages may miss.

Playwright is an easy-to-use, but powerful tool that automates end-to-end testing, and supports all modern browsers and platforms.

When coupled with LambdaTest (an AI-powered cloud-based test execution platform) it can be further scaled to run the Playwright scripts in parallel across 3000+ browser and device combinations:

>> Automated End-to-End Testing With Playwright

Course – Spring Sale 2025 – NPI EA (cat= Baeldung)
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Course – Spring Sale 2025 – NPI (cat=Baeldung)
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eBook – Guide Spring Cloud – NPI (cat=Cloud/Spring Cloud)
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1. Introduction

In this tutorial, we’ll learn how to use Spring Cloud Function.

We’ll build and run a simple Spring Cloud Function locally and then deploy it to AWS.

2. Spring Cloud Function Setup

To start with, let’s implement from scratch and test a simple project with two functions using different approaches:

  • A String reverser, using a plain method
  • And a greeter using a dedicated class

2.1. Maven Dependencies

The first thing we need to do is include the spring-cloud-starter-function-web dependency. This will act as our local adapter and brings in the necessary dependencies to run our function locally:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-function-web</artifactId>
    <version>1.0.1.RELEASE</version>
</dependency>

Stay tuned as we’ll modify this a bit when we are deploying to AWS.

2.2. Writing the Spring Cloud Function

With Spring Cloud Function, we can expose @Beans of type FunctionConsumer or Supplier as individual methods:

@SpringBootApplication
public class CloudFunctionApplication {

    public static void main(String[] args) {
        SpringApplication.run(CloudFunctionApplication.class, args);
    }

    @Bean
    public Function<String, String> reverseString() {
        return value -> new StringBuilder(value).reverse().toString();
    }
}

Like in this code, we can expose a reverse string feature as a Function, which our target functional platform can invoke.

2.3. Testing the Reverse String Function Locally

The spring-cloud-starter-function-web exposes the function as an HTTP endpoint. After we run the CloudFunctionApplication, we can curl our target to test it locally:

curl localhost:8080/reverseString -H "Content-Type: text/plain" -d "Baeldung User"

Note that the endpoint is the name of the bean. 

And as expected, we get the reversed string as output:

resU gnudleaB

2.4. Scanning Spring Cloud Function in Packages

Apart from exposing our method as a @Bean, we could also write our software as classes that implement the functional interface Function<T, R>:

public class Greeter implements Function<String, String> {

    @Override
    public String apply(String s) {
        return "Hello " + s + ", and welcome to Spring Cloud Function!!!";
    }
}

We can then specify the packages to scan for relevant beans in application.properties:

spring.cloud.function.scan.packages=com.baeldung.spring.cloudfunction.functions

2.5. Testing the Greeter Function Locally

Again, we can start the app and use curl to test the Greeter function:

curl localhost:8080/greeter -H "Content-Type: text/plain" -d "World"

Note that the endpoint is the name of the class that implements the Functional interface. 

And, no surprise, we get the expected greeting back:

Hello World, and welcome to Spring Cloud function!!!

3. Spring Cloud Function on AWS

What makes Spring Cloud Function so powerful is that we can build Spring enabled functions that are cloud agnostic. The function itself doesn’t need to know about how it was called or the environment it is deployed into. For example, we can easily deploy this greeter to AWS, Azure or Google Cloud platform without changing any of the business logic.

Since AWS Lambda is one of the popular serverless solutions, let’s focus on how to deploy our app into it.

So, let’s not wait any longer and deploy our function to the cloud!

3.1. Maven Dependencies

Remember the spring-cloud-starter-function-web dependency, which we added originally. Now it’s time to change that.

See, depending on where we are going to run the Spring Cloud Function, we need to add the appropriate dependency.

For AWS, we’ll use spring-cloud-function-adapter-aws:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-function-adapter-aws</artifactId>
</dependency>

Next, let’s add the required AWS dependencies to handle Lambda events:

<dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-lambda-java-events</artifactId>
    <version>2.0.2</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-lambda-java-core</artifactId>
    <version>1.1.0</version>
    <scope>provided</scope>
</dependency>

Finally, because we are going to upload the artifact generated by the maven build to AWS Lambda, we need to build an artifact that is shaded, meaning, it has all the dependencies exploded out as individual class files instead of jars.

The spring-boot-thin-layout dependency helps us to reduce the size of the artifact by excluding some dependencies that are not needed:

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-deploy-plugin</artifactId>
            <configuration>
                <skip>true</skip>
            </configuration>
        </plugin>
        <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>1.0.10.RELEASE</version>
                </dependency>
            </dependencies>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <configuration>
                <createDependencyReducedPom>false</createDependencyReducedPom>
                <shadedArtifactAttached>true</shadedArtifactAttached>
                <shadedClassifierName>aws</shadedClassifierName>
            </configuration>
        </plugin>
    </plugins>
</build>

3.2. AWS Handlers

If we want to expose our string reverser again via an HTTP request, then Spring Cloud Function AWS ships with SpringBootRequestHandler. It implements AWS’s RequestHandler and is in charge of dispatching the AWS request to our function.

public class MyStringHandlers extends SpringBootRequestHandler<String, String> {

}

Spring Cloud Function AWS also ships with SpringBootStreamHandler and FunctionInvokingS3EventHandler as other examples

Now, it may seem a bit odd that the MyStringHandlers is just an empty class but it plays an important role in both acting as the entry point of the Lambda function and also defining its input and output types.

As we’ll see in the screenshot below, we’ll provide the fully qualified name of this class in the Handler input field of the AWS Lambda configuration page.

3.3. How Does AWS Know Which Cloud Function to Invoke?

As it turns out, even if we have more than one Spring Cloud Function in our application, AWS can invoke only one of them.

In the next section, we’ll specify the cloud function name in an environment variable called FUNCTION_NAME on the AWS console.

4. Upload the Function to AWS and Test

Finally, let’s build our jar with maven, and then upload it via the AWS Console UI.

4.1. Create a Lambda Function on AWS Console and Configure It

On the AWS Lambda console page, in the Function code section, we can select a Java 8 runtime and simply click Upload.

After that, we need to indicate in the Handler field the fully-qualified name of the class that implements SpringBootRequestHandler, or com.baeldung.spring.cloudfunction.MyStringHandlers in our case:

cloud1

And then in Environment variables, we indicate which Spring function bean to invoke via the FUNCTION_NAME environment variable:

cloud2

And having done that, it’s time for us to test the Lambda function by creating a test event and supplying a sample string:

cloud3

4.2. Testing the Function on AWS

Now, we Save our test, then click the Test button.

And, as expected, we get the same output as what we got when we tested the function locally:

cloud4

4.3. Testing Another Function

Remember, we have one more function in our application: greeter. Let’s make sure that works too.

We’ll change the FUNCTION_NAME environment variable to greeter:

cloud5

Click the Save button and finally, the Test button again:

cloud6

5. Conclusion

In summary, though in its early stages, Spring Cloud Function is a powerful tool for decoupling the business logic from any specific runtime target.

With it, the same code can run as a web endpoint, on a cloud platform, or as a part of a stream. It abstracts away all of the transport details and infrastructure, allowing the developer to keep all the familiar tools and processes, and focus firmly on business logic.

The code backing this article is available on GitHub. Once you're logged in as a Baeldung Pro Member, start learning and coding on the project.
Baeldung Pro – NPI EA (cat = Baeldung)
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Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:

>> Explore a clean Baeldung

Once the early-adopter seats are all used, the price will go up and stay at $33/year.

Partner – Microsoft – NPI EA (cat = Spring Boot)
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Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.

Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.

To learn more about Java features on Azure Container Apps, visit the documentation page.

You can also ask questions and leave feedback on the Azure Container Apps GitHub page.

Partner – Orkes – NPI EA (cat = Spring)
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.

Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.

With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.

Try a 14-Day Free Trial of Orkes Conductor today.

Partner – Orkes – NPI EA (tag = Microservices)
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.

Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.

With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.

Try a 14-Day Free Trial of Orkes Conductor today.

eBook – HTTP Client – NPI EA (cat=HTTP Client-Side)
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The Apache HTTP Client is a very robust library, suitable for both simple and advanced use cases when testing HTTP endpoints. Check out our guide covering basic request and response handling, as well as security, cookies, timeouts, and more:

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eBook – Java Concurrency – NPI EA (cat=Java Concurrency)
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Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.

Get started with understanding multi-threaded applications with our Java Concurrency guide:

>> Download the eBook

eBook – Java Streams – NPI EA (cat=Java Streams)
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Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.

But these can also be overused and fall into some common pitfalls.

To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:

>> Join Pro and download the eBook

eBook – Persistence – NPI EA (cat=Persistence)
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Working on getting your persistence layer right with Spring?

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Course – LS – NPI EA (cat=REST)

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Get started with Spring Boot and with core Spring, through the Learn Spring course:

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Course – Spring Sale 2025 – NPI EA (cat= Baeldung)
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Course – Spring Sale 2025 – NPI (All)
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Partner – Microsoft – NPI (cat=Spring)
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Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.

Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.

To learn more about Java features on Azure Container Apps, visit the documentation page.

You can also ask questions and leave feedback on the Azure Container Apps GitHub page.

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