JarCastingConst Generator Maven Plugin
A simple maven plugin to generate util classes or objects containing compile time values for Java, Kotlin, and other JVM languages. Useful for dynamically including artifact version, build time or other build dependent values in your source for easy access.
Adding to your maven project
To enable constant generation, add the following plugin execution to your build config (build > plugins):
<plugin>
<groupId>com.mktiti</groupId>
<artifactId>const-generator-maven-plugin</artifactId>
<version>1.1</version>
<configuration>
<packageName>my.project.generated</packageName>
</configuration>
<executions>
<execution>
<id>generate-const</id>
<phase>generate-sources</phase>
<goals>
<goal>generate</goal>
</goals>
</execution>
</executions>
</plugin>
Code generation happens on the generate goal, invoke it with mvn const-generator:generate.
To generate automatically, add the goal execution to the generate-sources phase (as seen above).
Also add the output directory (${project.build.directory}/src/main/{java/kotlin} by default, usually target/src/main/{java/kotlin}) to your sources, and optionally mark the generated directory as 'Generated sources' or similar in your IDE.
Java compiler sample config (build > plugins):
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<generatedSourcesDirectory>${project.build.directory}/src/main/java</generatedSourcesDirectory>
<!-- Other configs -->
</configuration>
<!-- Executions, etc. -->
</plugin>
Kotlin compiler sample config (build > plugins):
<plugin>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-maven-plugin</artifactId>
<version>${kotlin.version}</version>
<configuration>
<sourceDirs>
<sourceDir>${project.basedir}/src/main/kotlin</sourceDir>
<sourceDir>${project.build.directory}/src/main/kotlin</sourceDir>
</sourceDirs>
<!-- Other configs -->
</configuration>
<!-- Executions, etc. -->
</plugin>
Now you can access the generated properties from your code. (Version is added by default)
// Java
System.out.println("Running version: " + ProjectInfo.version); // Running version: 1.0-SNAPSHOT
// Kotlin
println("Running version: ${ProjectInfo.version}") // Running version: 1.0-SNAPSHOT
Multiple executions are supported for multiple file generation (each with their own config in the execution tag).
Configuration
Settings
| Config key | Usage | Default |
|---|---|---|
outputDirectory |
Path to generate the sources in | ${project.build.directory}/src/main/ (e.g. target/src/main) |
type |
Type of source to generate (java/kotlin) | java |
packageName |
Package of the generated class/object | No default |
className |
Name of the generated class/object | ProjectInfo |
visibility |
Visibility modifier of the class/object and members One of PUBLIC, PACKAGE_PRIVATE, DEFAULT |
PUBLIC |
useGetters |
Whether to use static getters (without backing fields) or static fields | false |
addVersion |
Sets whether the project version should be added | true |
values |
Key-Value map of the values to be added (e.g. <foo>bar</foo>) | empty |
Examples
Basic example with defaults only
By default the project version is added (as it is the most often used option), this can be disabled through the addVersion option.
The only required option is packageName.
Config:
<configuration>
<packageName>my.project.generated</packageName>
</configuration>
Output (target/src/main/java/my/project/generated/ProjectInfo.java):
package my.project.generated;
// Generated by const-generator-maven-plugin at 2019-07-17T23:47:46.924
public final class ProjectInfo {
private ProjectInfo() {
throw new AssertionError("Generated static utility class, should not be instantiated");
}
public static final String version = "1.0-SNAPSHOT";
}
Custom values
You can add your own custom values (constants or maven properties) using the values map.
Config:
<configuration>
<packageName>my.project.generated</packageName>
<values>
<foo>bar</foo>
<empty></empty>
<builtAt>${maven.build.timestamp}</builtAt>
<builtBy>${user.name}</builtBy>
</values>
</configuration>
Output (target/src/main/java/my/project/generated/ProjectInfo.java):
package my.project.generated;
// Generated by const-generator-maven-plugin at 2019-07-17T23:52:54.796
public final class ProjectInfo {
private ProjectInfo() {
throw new AssertionError("Generated static utility class, should not be instantiated");
}
public static final String builtBy = "titi";
public static final String builtAt = "2019-07-17T21:52:54Z";
public static final String foo = "bar";
public static final String version = "1.0-SNAPSHOT";
public static final String empty = "";
}
Getters instead of fields
Change the generation type to getters with useGetters.
Config:
<configuration>
<packageName>my.project.generated</packageName>
<values>
<foo>bar</foo>
</values>
<useGetters>true</useGetters>
</configuration>
Output (target/src/main/java/my/project/generated/ProjectInfo.java):
package my.project.generated;
// Generated by const-generator-maven-plugin at 2019-07-17T23:56:03.046
public final class ProjectInfo {
private ProjectInfo() {
throw new AssertionError("Generated static utility class, should not be instantiated");
}
public static String getFoo() {
return "bar";
}
public static String getVersion() {
return "1.0-SNAPSHOT";
}
}
Kotlin generation
Beside java, kotlin source generation is also supported, this is to make integration for kotlin-only projects easier.
Kotlin generation is designed as to allow easy access from java code.
Use the type config option to set the generation type (kotlin/java).
Config:
<configuration>
<packageName>my.project.generated</packageName>
<type>kotlin</type>
<values>
<foo>bar</foo>
</values>
</configuration>
Output (target/src/main/kotlin/generated/ProjectInfo.kt):
@file:JvmName("ProjectInfo")
package my.project.generated
// Generated by const-generator-maven-plugin at 2019-07-17T23:58:25.138
public object ProjectInfo {
@JvmField public val foo: String = "bar"
@JvmField public val version: String = "1.0-SNAPSHOT"
}
Kotlin getters
Config:
<configuration>
<packageName>my.project.generated</packageName>
<type>kotlin</type>
<values>
<foo>bar</foo>
</values>
<useGetters>true</useGetters>
</configuration>
Output (target/src/main/kotlin/generated/ProjectInfo.kt):
@file:JvmName("ProjectInfo")
package my.project.generated
// Generated by const-generator-maven-plugin at 2019-07-18T00:16:31.070
public object ProjectInfo {
@JvmStatic @get:JvmName("getFoo") public val foo: String = "bar"
@JvmStatic @get:JvmName("getVersion") public val version: String = "1.0-SNAPSHOT"
}
Other settings
There are various other config settings to use.
Config:
<configuration>
<packageName>my.project.generated</packageName>
<type>java</type>
<className>MetaInfo</className>
<addVersion>false</addVersion>
<visibility>PUBLIC</visibility>
<outputDirectory>${project.basedir}/gen</outputDirectory>
<values>
<foo>bar</foo>
</values>
</configuration>
Output (gen/java/my/project/generated/MetaInfo.java):
package my.project.generated;
// Generated by const-generator-maven-plugin at 2019-07-18T00:02:08.427
public final class MetaInfo {
private MetaInfo() {
throw new AssertionError("Generated static utility class, should not be instantiated");
}
public static final String foo = "bar";
}