The kotlin-maven-plugin compiles Kotlin sources and modules. Currently, only Maven v3 is supported.
Define the version of Kotlin you want to use via a kotlin.version property:
<properties>
<kotlin.version>%kotlinVersion%</kotlin.version>
</properties>
Kotlin has an extensive standard library that can be used in your applications. To use the standard library in your project, add the following dependency in the pom file:
<dependencies>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-stdlib</artifactId>
<version>${kotlin.version}</version>
</dependency>
</dependencies>
If you're targeting JDK 7 or JDK 8, you can use extended versions of the Kotlin standard library. They contain
additional extension functions for APIs added in new JDK versions. Instead of kotlin-stdlib
, use kotlin-stdlib-jdk7
or kotlin-stdlib-jdk8
, depending on your JDK version.
For Kotlin versions older that 1.2, use
kotlin-stdlib-jre7
andkotlin-stdlib-jre8
.
{type="note"}
If your project uses Kotlin reflection
or testing facilities, you need to add the corresponding dependencies as well.
The artifact IDs are kotlin-reflect
for the reflection library, and kotlin-test
and kotlin-test-junit
for the testing libraries.
To compile source code, specify the source directories in the <build>
tag:
<build>
<sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
<testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
</build>
The Kotlin Maven Plugin needs to be referenced to compile the sources:
<build>
<plugins>
<plugin>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-maven-plugin</artifactId>
<version>${kotlin.version}</version>
<executions>
<execution>
<id>compile</id>
<goals>
<goal>compile</goal>
</goals>
</execution>
<execution>
<id>test-compile</id>
<goals>
<goal>test-compile</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
To compile projects that include Kotlin and Java source code, invoke the Kotlin compiler before the Java compiler.
In maven terms that means that kotlin-maven-plugin
should be run before maven-compiler-plugin
using the following method,
making sure that the kotlin
plugin comes before the maven-compiler-plugin
in your pom.xml
file:
<build>
<plugins>
<plugin>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-maven-plugin</artifactId>
<version>${kotlin.version}</version>
<executions>
<execution>
<id>compile</id>
<goals>
<goal>compile</goal>
</goals>
<configuration>
<sourceDirs>
<sourceDir>${project.basedir}/src/main/kotlin</sourceDir>
<sourceDir>${project.basedir}/src/main/java</sourceDir>
</sourceDirs>
</configuration>
</execution>
<execution>
<id>test-compile</id>
<goals> <goal>test-compile</goal> </goals>
<configuration>
<sourceDirs>
<sourceDir>${project.basedir}/src/test/kotlin</sourceDir>
<sourceDir>${project.basedir}/src/test/java</sourceDir>
</sourceDirs>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.5.1</version>
<executions>
<!-- Replacing default-compile as it is treated specially by maven -->
<execution>
<id>default-compile</id>
<phase>none</phase>
</execution>
<!-- Replacing default-testCompile as it is treated specially by maven -->
<execution>
<id>default-testCompile</id>
<phase>none</phase>
</execution>
<execution>
<id>java-compile</id>
<phase>compile</phase>
<goals>
<goal>compile</goal>
</goals>
</execution>
<execution>
<id>java-test-compile</id>
<phase>test-compile</phase>
<goals>
<goal>testCompile</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
To make your builds faster, you can enable incremental compilation for Maven by defining the
kotlin.compiler.incremental
property:
<properties>
<kotlin.compiler.incremental>true</kotlin.compiler.incremental>
</properties>
Alternatively, run your build with the -Dkotlin.compiler.incremental=true
option.
See the description of Kotlin annotation processing tool (kapt
).
To create a small Jar file containing just the code from your module, include the following under build->plugins
in your Maven pom.xml file, where main.class
is defined as a property and points to the main Kotlin or Java class:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.6</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<mainClass>${main.class}</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
To create a self-contained Jar file containing the code from your module along with dependencies, include the following
under build->plugins
in your Maven pom.xml file, where main.class
is defined as a property and points to
the main Kotlin or Java class:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.6</version>
<executions>
<execution>
<id>make-assembly</id>
<phase>package</phase>
<goals> <goal>single</goal> </goals>
<configuration>
<archive>
<manifest>
<mainClass>${main.class}</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</execution>
</executions>
</plugin>
This self-contained jar file can be passed directly to a JRE to run your application:
java -jar target/mymodule-0.0.1-SNAPSHOT-jar-with-dependencies.jar
Additional options and arguments for the compiler can be specified as tags under the <configuration>
element of the
Maven plugin node:
<plugin>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-maven-plugin</artifactId>
<version>${kotlin.version}</version>
<executions>...</executions>
<configuration>
<nowarn>true</nowarn> <!-- Disable warnings -->
<args>
<arg>-Xjsr305=strict</arg> <!-- Enable strict mode for JSR-305 annotations -->
...
</args>
</configuration>
</plugin>
Many of the options can also be configured through properties:
<project ...>
<properties>
<kotlin.compiler.languageVersion>1.0</kotlin.compiler.languageVersion>
</properties>
</project>
The following attributes are supported:
Name | Property name | Description | Possible values | Default value |
---|---|---|---|---|
nowarn |
Generate no warnings | true, false | false | |
languageVersion |
kotlin.compiler.languageVersion | Provide source compatibility with the specified version of Kotlin | "1.2" (DEPRECATED), "1.3", "1.4", "1.5" (EXPERIMENTAL) | |
apiVersion |
kotlin.compiler.apiVersion | Allow using declarations only from the specified version of bundled libraries | "1.2" (DEPRECATED), "1.3", "1.4", "1.5" (EXPERIMENTAL) | |
sourceDirs |
The directories containing the source files to compile | The project source roots | ||
compilerPlugins |
Enabled compiler plugins | [] | ||
pluginOptions |
Options for compiler plugins | [] | ||
args |
Additional compiler arguments | [] |
Name | Property name | Description | Possible values | Default value |
---|---|---|---|---|
jvmTarget |
kotlin.compiler.jvmTarget |
Target version of the generated JVM bytecode | "1.6", "1.8", "9", "10", "11", "12", "13", "14", "15" | "1.6" |
jdkHome |
kotlin.compiler.jdkHome |
Include a custom JDK from the specified location into the classpath instead of the default JAVA_HOME |
Name | Property name | Description | Possible values | Default value |
---|---|---|---|---|
outputFile |
Destination *.js file for the compilation result | |||
metaInfo |
Generate .meta.js and .kjsm files with metadata. Use to create a library | true, false | true | |
sourceMap |
Generate source map | true, false | false | |
sourceMapEmbedSources |
Embed source files into source map | "never", "always", "inlining" | "inlining" | |
sourceMapPrefix |
Add the specified prefix to paths in the source map | |||
moduleKind |
The kind of JS module generated by the compiler | "umd", "commonjs", "amd", "plain" | "umd" |
The standard JavaDoc generation plugin (maven-javadoc-plugin
) does not support Kotlin code.
To generate documentation for Kotlin projects, use Dokka;
please refer to the Dokka README
for configuration instructions. Dokka supports mixed-language projects and can generate output in multiple
formats, including standard JavaDoc.
For OSGi support see the Kotlin OSGi page.
An example Maven project can be downloaded from the GitHub repository