spring-cloud / spring-cloud-stream

Framework for building Event-Driven Microservices
http://cloud.spring.io/spring-cloud-stream
Apache License 2.0
1.01k stars 613 forks source link
cloud-native event-driven-microservices messaging microservices reactive stream-processing

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== Introduction Spring Cloud Stream is a framework for building message-driven microservice applications. Spring Cloud Stream builds upon Spring Boot to create standalone, production-grade Spring applications and uses Spring Integration to provide connectivity to message brokers. It provides opinionated configuration of middleware from several vendors, introducing the concepts of persistent publish-subscribe semantics, consumer groups, and partitions. These are called binder implementations in the parlance of Spring Cloud Stream. Out of the box, Spring Cloud Stream provides binder implementations for Apache Kafka and RabbitMQ. While these two binder implementations are based on Message Channels, Spring Cloud Stream also provides another binder implementation for Kafka Streams that does not use message channels, but native Kafka Streams types such as KStream, KTable etc.

Below, you can find more information on how to use these various out-of-the-box binder implementations in your applications.

== Apache Kafka Binder

=== Usage

To use Apache Kafka binder, you need to add spring-cloud-stream-binder-kafka as a dependency to your Spring Cloud Stream application, as shown in the following example for Maven:

[source,xml]

org.springframework.cloud spring-cloud-stream-binder-kafka

Alternatively, you can also use the Spring Cloud Stream Kafka Starter, as shown in the following example for Maven:

[source,xml]

org.springframework.cloud spring-cloud-starter-stream-kafka

== Apache Kafka Streams Binder

=== Usage

To use Apache Kafka Streams binder, you need to add spring-cloud-stream-binder-kafka-streams as a dependency to your Spring Cloud Stream application, as shown in the following example for Maven:

[source,xml]

org.springframework.cloud spring-cloud-stream-binder-kafka-streams

== RabbitMQ Binder === Usage

To use the RabbitMQ binder, you can add it to your Spring Cloud Stream application, by using the following Maven coordinates:

[source,xml]

org.springframework.cloud spring-cloud-stream-binder-rabbit

Alternatively, you can use the Spring Cloud Stream RabbitMQ Starter, as follows:

[source,xml]

org.springframework.cloud spring-cloud-starter-stream-rabbit

== Resources

For more information, please visit the https://spring.io/projects/spring-cloud-stream[project website]:

== Building

:jdkversion: 17

=== Basic Compile and Test

To build the source you will need to install JDK {jdkversion}.

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

NOTE: 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.

NOTE: 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.

The projects that require middleware (i.e. Redis) for testing generally require that a local instance of Docker is installed and running.

=== Documentation

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.

=== Working with the code If you don't have an IDE preference we would recommend that you use https://www.springsource.com/developer/sts[Spring Tools Suite] or https://eclipse.org[Eclipse] when working with the code. We use the https://eclipse.org/m2e/[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.

==== Activate the Spring Maven profile Spring Cloud projects require the 'spring' Maven profile to be activated to resolve the spring milestone and snapshot repositories. Use your preferred IDE to set this profile to be active, or you may experience build errors.

==== Importing into eclipse with m2eclipse We recommend the https://eclipse.org/m2e/[m2eclipse] eclipse plugin when working with eclipse. If you don't already have m2eclipse installed it is available from the "eclipse marketplace".

NOTE: 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.

==== Importing into eclipse without m2eclipse If you prefer not to use m2eclipse you can generate eclipse project metadata using the following command:

[indent=0]

$ ./mvnw eclipse:eclipse

The generated eclipse projects can be imported by selecting import existing projects from the file menu.

== Contributing

:spring-cloud-build-branch: master

Spring Cloud is released under the non-restrictive Apache 2.0 license, and follows a very standard Github development process, using Github tracker for issues and merging pull requests into master. If you want to contribute even something trivial please do not hesitate, but follow the guidelines below.

=== Sign the Contributor License Agreement Before we accept a non-trivial patch or pull request we will need you to sign the https://cla.pivotal.io/sign/spring[Contributor License Agreement]. Signing the contributor's agreement does not grant anyone commit rights to the main repository, but it does mean that we can accept your contributions, and you will get an author credit if we do. Active contributors might be asked to join the core team, and given the ability to merge pull requests.

=== Code of Conduct This project adheres to the Contributor Covenant https://github.com/spring-cloud/spring-cloud-build/blob/master/docs/src/main/asciidoc/code-of-conduct.adoc[code of conduct]. By participating, you are expected to uphold this code. Please report unacceptable behavior to spring-code-of-conduct@pivotal.io.

=== Code Conventions and Housekeeping None of these is essential for a pull request, but they will all help. They can also be added after the original pull request but before a merge.

=== Checkstyle

Spring Cloud Build comes with a set of checkstyle rules. You can find them in the spring-cloud-build-tools module. The most notable files under the module are:

.spring-cloud-build-tools/

└── src    ├── checkstyle    │   └── checkstyle-suppressions.xml <3>    └── main    └── resources    ├── checkstyle-header.txt <2>    └── checkstyle.xml <1>

<1> Default Checkstyle rules <2> File header setup <3> Default suppression rules ==== Checkstyle configuration Checkstyle rules are *disabled by default*. To add checkstyle to your project just define the following properties and plugins. .pom.xml ---- true <1> true <2> true <3> <4> io.spring.javaformat spring-javaformat-maven-plugin <5> org.apache.maven.plugins maven-checkstyle-plugin <5> org.apache.maven.plugins maven-checkstyle-plugin ---- <1> Fails the build upon Checkstyle errors <2> Fails the build upon Checkstyle violations <3> Checkstyle analyzes also the test sources <4> Add the Spring Java Format plugin that will reformat your code to pass most of the Checkstyle formatting rules <5> Add checkstyle plugin to your build and reporting phases If you need to suppress some rules (e.g. line length needs to be longer), then it's enough for you to define a file under `${project.root}/src/checkstyle/checkstyle-suppressions.xml` with your suppressions. Example: .projectRoot/src/checkstyle/checkstyle-suppresions.xml ---- ---- It's advisable to copy the `${spring-cloud-build.rootFolder}/.editorconfig` and `${spring-cloud-build.rootFolder}/.springformat` to your project. That way, some default formatting rules will be applied. You can do so by running this script: ```bash $ curl https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/.editorconfig -o .editorconfig $ touch .springformat ``` === IDE setup ==== Intellij IDEA In order to setup Intellij you should import our coding conventions, inspection profiles and set up the checkstyle plugin. The following files can be found in the https://github.com/spring-cloud/spring-cloud-build/tree/master/spring-cloud-build-tools[Spring Cloud Build] project. .spring-cloud-build-tools/ ---- └── src    ├── checkstyle    │   └── checkstyle-suppressions.xml <3>    └── main    └── resources    ├── checkstyle-header.txt <2>    ├── checkstyle.xml <1>    └── intellij       ├── Intellij_Project_Defaults.xml <4>       └── Intellij_Spring_Boot_Java_Conventions.xml <5> ---- <1> Default Checkstyle rules <2> File header setup <3> Default suppression rules <4> Project defaults for Intellij that apply most of Checkstyle rules <5> Project style conventions for Intellij that apply most of Checkstyle rules .Code style image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/{spring-cloud-build-branch}/docs/src/main/asciidoc/images/intellij-code-style.png[Code style] Go to `File` -> `Settings` -> `Editor` -> `Code style`. There click on the icon next to the `Scheme` section. There, click on the `Import Scheme` value and pick the `Intellij IDEA code style XML` option. Import the `spring-cloud-build-tools/src/main/resources/intellij/Intellij_Spring_Boot_Java_Conventions.xml` file. .Inspection profiles image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/{spring-cloud-build-branch}/docs/src/main/asciidoc/images/intellij-inspections.png[Code style] Go to `File` -> `Settings` -> `Editor` -> `Inspections`. There click on the icon next to the `Profile` section. There, click on the `Import Profile` and import the `spring-cloud-build-tools/src/main/resources/intellij/Intellij_Project_Defaults.xml` file. .Checkstyle To have Intellij work with Checkstyle, you have to install the `Checkstyle` plugin. It's advisable to also install the `Assertions2Assertj` to automatically convert the JUnit assertions image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/{spring-cloud-build-branch}/docs/src/main/asciidoc/images/intellij-checkstyle.png[Checkstyle] Go to `File` -> `Settings` -> `Other settings` -> `Checkstyle`. There click on the `+` icon in the `Configuration file` section. There, you'll have to define where the checkstyle rules should be picked from. In the image above, we've picked the rules from the cloned Spring Cloud Build repository. However, you can point to the Spring Cloud Build's GitHub repository (e.g. for the `checkstyle.xml` : `https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-build-tools/src/main/resources/checkstyle.xml`). We need to provide the following variables: - `checkstyle.header.file` - please point it to the Spring Cloud Build's, `spring-cloud-build-tools/src/main/resources/checkstyle-header.txt` file either in your cloned repo or via the `https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-build-tools/src/main/resources/checkstyle-header.txt` URL. - `checkstyle.suppressions.file` - default suppressions. Please point it to the Spring Cloud Build's, `spring-cloud-build-tools/src/checkstyle/checkstyle-suppressions.xml` file either in your cloned repo or via the `https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-build-tools/src/checkstyle/checkstyle-suppressions.xml` URL. - `checkstyle.additional.suppressions.file` - this variable corresponds to suppressions in your local project. E.g. you're working on `spring-cloud-contract`. Then point to the `project-root/src/checkstyle/checkstyle-suppressions.xml` folder. Example for `spring-cloud-contract` would be: `/home/username/spring-cloud-contract/src/checkstyle/checkstyle-suppressions.xml`. IMPORTANT: Remember to set the `Scan Scope` to `All sources` since we apply checkstyle rules for production and test sources. === Duplicate Finder Spring Cloud Build brings along the `basepom:duplicate-finder-maven-plugin`, that enables flagging duplicate and conflicting classes and resources on the java classpath. ==== Duplicate Finder configuration Duplicate finder is *enabled by default* and will run in the `verify` phase of your Maven build, but it will only take effect in your project if you add the `duplicate-finder-maven-plugin` to the `build` section of the projecst's `pom.xml`. .pom.xml [source,xml] ---- org.basepom.maven duplicate-finder-maven-plugin ---- For other properties, we have set defaults as listed in the https://github.com/basepom/duplicate-finder-maven-plugin/wiki[plugin documentation]. You can easily override them but setting the value of the selected property prefixed with `duplicate-finder-maven-plugin`. For example, set `duplicate-finder-maven-plugin.skip` to `true` in order to skip duplicates check in your build. If you need to add `ignoredClassPatterns` or `ignoredResourcePatterns` to your setup, make sure to add them in the plugin configuration section of your project: [source,xml] ---- org.basepom.maven duplicate-finder-maven-plugin org.joda.time.base.BaseDateTime .*module-info changelog.txt ----