Build only what has changed.
This is a Maven extension to run incremental builds on a multi-module Maven project. This extension automatically determines the modules that have changed since the last build and builds only the changed modules. It supports both single-threaded and multi-threaded (aka parallel) builds. Maven supports building selective projects and their downstream projects using the -pl and -amd flags. This plugin does the same but automatically determines the list of changed projects.
- Java 8
- Multi-module Maven project
This extension is not yet published to Maven Central since it is in a POC stage. Hence it will have to be installed manually. Clone this Git repo (or download it) and run "mvn clean install" in this project's directory. This will install the extension to your Maven repository and will be available for other Maven projects to use. In order to use this extension in a Maven project, Create a .mvn folder in your top-level Maven project directory. Create a extensions.xml file in the .mvn folder and add the following to the extensions.xml fiile:
<extensions xmlns="http://maven.apache.org/EXTENSIONS/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/EXTENSIONS/1.0.0 http://maven.apache.org/xsd/core-extensions-1.0.0.xsd">
<extension>
<groupId>com.github.sudhanwadindorkar</groupId>
<artifactId>incremental-maven-builder</artifactId>
<version>xxx</version>
</extension>
</extensions>Replace the "xxx" in the version tag with the version from this project's pom.xml.
mvn -b builder-name -Dbuilder-option maven-switch
The incremental builder can be invoked by specifying the builder name using the -b builder-name switch. Use incremental as the builder name for the single-threaded builder and incremental-multithreaded for the multi-threaded builder. The multi-threaded builder takes the same options as Maven's multi-threaded builder. See https://cwiki.apache.org/confluence/display/MAVEN/Parallel+builds+in+Maven+3 for more details on Maven's parallel build feature. The incremental builder will display the re-calculated reactor and proceed with bulding only the changed projects.
The following builder options are supported and can be specified as properties:
incremental.skip.build=true|false - If set to true, does not run the actual build. The value of the flag is false by default. This flag is useful if you want to just see the re-calculated reactor.
incremental.reactor.detailed=true|false - If set to true, prints a detailed reactor which includes the list of changed projects, dependent projects & skipped projects. The value of the flag is false by default.
The maven switches like -rf, -X are also supported.
Here are some examples:
mvn -b incremental clean install - Runs clean install on the changed projects.
mvn -b incremental-multithreaded clean install -T 1C - Runs clean install on the changed projects using the multi-threaded builder.
mvn -b incremental -Dincremental.skip.build -Dincremental.reactor.detailed clean - Just determines the changed projects & prints the list of the changed projects.
mvn -b incremental -Dincremental.reactor.detailed clean install - Prints detailed reactor information & then runs clean install on the changed projects.
mvn -b incremental -X clean install - Runs clean install on the changed projects while printing debug level information.
tldr; This extension requires the install phase to be run for functioning.
The incremental builder determines the list of changed projects by comparing the last modified timestamps of a module's source artifacts with the last modified timestamp of the module artifact (.war, .jar, etc) installed in the local Maven repository (the .m2/repository folder usually). The source artifacts for a module include:
- The module's pom.xml.
- The script source directory (if any). e.g. src/main/scripts.
- The source directory e.g. src/main/java
- The resource directories.
If at least one source artifact is found such that it's last modified timestamp is after the last modified timestamp of the module artifact installed in the local Maven repository, the the module is added to the list of projects to be built.
Are you facing any issues running this extension? Would you like some improvements? Please report an issue at https://github.com/sudhanwadindorkar/incremental-maven-builder/issues. Please do include the command output with debug logs enabled via the -X flag.
- Unit Tests.
- Publish to Maven Central.
- Get feedback & suggestions from users.
- Determine the changed projects based on the artifacts in the target folder i.e. support for the package phase (only if someone asks for it).
- What would you like?
This extension has been inspired by Karl Heinz Marbaise's Maven extension for incremental Maven builds - https://github.com/khmarbaise/incremental-module-builder. My thanks to Karl Heinz Marbaise for making it available.