Spring Cloud Function is a project with the following high-level goals:
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Promote the implementation of business logic via functions.
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Decouple the development lifecycle of business logic from any specific runtime target so that the same code can run as a web endpoint, a stream processor, or a task.
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Support a uniform programming model across serverless providers, as well as the ability to run standalone (locally or in a PaaS).
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Enable Spring Boot features (auto-configuration, dependency injection, metrics) on serverless providers.
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.
Here’s a complete, executable, testable Spring Boot application (implementing a simple string manipulation):
@SpringBootApplication
public class Application {
@Bean
public Function<Flux<String>, Flux<String>> uppercase() {
return flux -> flux.map(value -> value.toUpperCase());
}
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}It’s just a Spring Boot application, so it can be built, run and
tested, locally and in a CI build, the same way as any other Spring
Boot application. The Function is from java.util and Flux is a
Reactive Streams Publisher from
Project Reactor. The function can be
accessed over HTTP or messaging.
Spring Cloud Function has 4 main features:
In the nutshell Spring Cloud Function provides the following features:
1. Wrappers for @Beans of type Function, Consumer and
Supplier, exposing them to the outside world as either HTTP
endpoints and/or message stream listeners/publishers with RabbitMQ, Kafka etc.
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Choice of programming styles - reactive, imperative or hybrid.
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Function composition and adaptation (e.g., composing imperative functions with reactive).
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Support for reactive function with multiple inputs and outputs allowing merging, joining and other complex streaming operation to be handled by functions.
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Transparent type conversion of inputs and outputs.
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Packaging functions for deployments, specific to the target platform (e.g., Project Riff, AWS Lambda and more)
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Adapters to expose function to the outside world as HTTP endpoints etc.
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Deploying a JAR file containing such an application context with an isolated classloader, so that you can pack them together in a single JVM.
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Compiling strings which are Java function bodies into bytecode, and then turning them into
@Beansthat can be wrapped as above. -
Adapters for AWS Lambda, Azure, Apache OpenWhisk and possibly other "serverless" service providers.
Build from the command line (and "install" the samples):
$ ./mvnw clean install
(If you like to YOLO add -DskipTests.)
Run one of the samples, e.g.
$ java -jar spring-cloud-function-samples/function-sample/target/*.jar
This runs the app and exposes its functions over HTTP, so you can convert a string to uppercase, like this:
$ curl -H "Content-Type: text/plain" localhost:8080/uppercase -d Hello HELLO
You can convert multiple strings (a Flux<String>) by separating them
with new lines
$ curl -H "Content-Type: text/plain" localhost:8080/uppercase -d 'Hello > World' HELLOWORLD
(You can use QJ in a terminal to insert a new line in a literal
string like that.)
To build the source you will need to install JDK 1.7.
Spring Cloud uses Maven for most build-related activities, and you should be able to get off the ground quite quickly by cloning the project you are interested in and typing
$ ./mvnw install
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Note
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You can also install Maven (>=3.3.3) yourself and run the mvn command
in place of ./mvnw in the examples below. If you do that you also
might need to add -P spring if your local Maven settings do not
contain repository declarations for spring pre-release artifacts.
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Note
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Be aware that you might need to increase the amount of memory
available to Maven by setting a MAVEN_OPTS environment variable with
a value like -Xmx512m -XX:MaxPermSize=128m. We try to cover this in
the .mvn configuration, so if you find you have to do it to make a
build succeed, please raise a ticket to get the settings added to
source control.
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For hints on how to build the project look in .travis.yml if there
is one. There should be a "script" and maybe "install" command. Also
look at the "services" section to see if any services need to be
running locally (e.g. mongo or rabbit). Ignore the git-related bits
that you might find in "before_install" since they’re related to setting git
credentials and you already have those.
The projects that require middleware generally include a
docker-compose.yml, so consider using
Docker Compose to run the middeware servers
in Docker containers. See the README in the
scripts demo
repository for specific instructions about the common cases of mongo,
rabbit and redis.
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Note
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If all else fails, build with the command from .travis.yml (usually
./mvnw install).
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The spring-cloud-build module has a "docs" profile, and if you switch
that on it will try to build asciidoc sources from
src/main/asciidoc. As part of that process it will look for a
README.adoc and process it by loading all the includes, but not
parsing or rendering it, just copying it to ${main.basedir}
(defaults to ${basedir}, i.e. the root of the project). If there are
any changes in the README it will then show up after a Maven build as
a modified file in the correct place. Just commit it and push the change.
If you don’t have an IDE preference we would recommend that you use Spring Tools Suite or Eclipse when working with the code. We use the m2eclipse eclipse plugin for maven support. Other IDEs and tools should also work without issue as long as they use Maven 3.3.3 or better.
We recommend the m2eclipse eclipse plugin when working with eclipse. If you don’t already have m2eclipse installed it is available from the "eclipse marketplace".
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Note
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Older versions of m2e do not support Maven 3.3, so once the
projects are imported into Eclipse you will also need to tell
m2eclipse to use the right profile for the projects. If you
see many different errors related to the POMs in the projects, check
that you have an up to date installation. If you can’t upgrade m2e,
add the "spring" profile to your settings.xml. Alternatively you can
copy the repository settings from the "spring" profile of the parent
pom into your settings.xml.
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Please refer to this Spring Cloud documentation to learn more about the licensing, Contributor License Agreement, Code of Conduct, Code Conventions and Checkstyle Configuration.