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KBean is the central concept of the execution engine. KBeans are classes with declared executable methods. There is only one KBean instance by KBean class in any given Jeka project (JkRuntime).

KBean classes share the following characteristics :

  • They extend KBean class.
  • They may declare public void methods without taking any arguments. All these methods can be invoked from the command line.
  • They may declare public fields (aka KBean properties). These field values can be injected from the command line. These can also be non-public fields annotated with @JkDoc.
  • They must provide a no-arg constructor
  • They may override init() method
  • They must be instantiated by the execution engine and not from the user code.

Simple Example

The following KBeans expose the cleanPublish method which delegates the creation of jar files to the 'project' KBean. ProjectKBean is available on the Jeka classpath as it is part of the standard KBeans bundled in the JeKa distribution.

import dev.jeka.core.api.project.JkProject;

@JkDoc("A simple example to illustrate KBean concept.")
public class SimpleJkBean extends KBean {

    final ProjectKBean projectKBean = load(ProjectKBean.class);  // Instantiate KBean or return singleton instance.

    protected void init() {  // When init() is invoked, projectKBean field instances has already been injected.

    @JkDoc("Clean, compile, test, create jar files, and publish them.")
    public void cleanPublish() {


KBean Commands

A KBean command is an instance method of a KBean class that can be invoked from the command line. In order to be considered as a command, a method must :

  • be public
  • be an instance method
  • take no argument
  • return void

KBean Attributes

A KBean attribute is a public instance field of a KBean class. Its value can be injected from the command line, or from property file. It can be also non-public fields annotated with @JkDoc.

Attributes can be annotated with @JkInjectProperty("") to inject the value of a property within.

For more details on field accepted types, see dev.jeka.core.tool.FieldInjector#parse method.

KBean properties can also be nested composite objects, see example in ProjectKBean#pack field.

Naming KBeans

In order to be referenced conveniently, KBeans can be called by names. For any given JkBean class, accepted names are :

  1. Full qualified class name
  2. Uncapitalized simple class name (e.g. 'myBuild' matches 'org.example.MyBuild')
  3. Uncapitalized simple class Name without 'JkBean' suffix (.g. 'project' matches 'dev.jeka.core.tool.builtin.project.ProjectKBean')


Execute jeka, at the root of a project to display KBeans present in Jeka classpath.

Document KBeans

KBean classes, methods, and properties can be annotated with @JkDoc annotation in order to provide self documentation.

Text within these annotations is displayed when invoking help method on the console.

Invoke KBeans

From Command Line

KBean methods can be invoked from the command line using

jeka [kbeanName]#methoName [kbeanName]#[propertyName]=xxx

Many methods/properties can be invoked in a single command line.


[kbeanName] prefix can be omitted. By default, it will be resolved on the bean mentioned by the -kb= option, or the first KBean found in def dir, if the option is not present. Search is executed by alphabetical order of fully qualified class names. Example : jeka #toSomething #aProperty=xxxx It is also possible to refer to the default KBean by using kb# prefix in place of #. Example : jeka kb#toSomething kb#aProperty=xxxx

From IntelliJ Jeka Plugin

[IntelliJ Jeka Plugin] allows the invocation of methods directly from the editor or the explorer tool window.

From naked IDE

KBean methods can also be launched/debugged from IDE using classic main methods.

In KBean class, declare one or several main methods as :

 public static void main(String[] args) {
        JkInit.instanceOf(MyBuild.class, args).cleanPack();

  public static class Release {
      public static void main(String[] args) {
          JkInit.instanceOf(MyBuild.class, args, "-runIT").release();
KBean must be instantiated using JkInit#instanceOf in order for it to be set up properly.

The arguments passed in the main method are interpreted as command line arguments.

Launching or debugging this way is performant as all build classes and their dependencies are already on classpath. Therefore, no compilation or dependency resolution is needed.


Be careful to launch the main method using module dir as working dir. On IntelliJ, this is not the default (it uses project dir).

To change intelliJ defaults, follow : Edit Configurations | Edit configuration templates... | Application | Working Directory : $MODULE_DIR$.

Sometimes, you may need to mimic the command line behavior more closely, for debugging purposes or to pass '@' arguments.

  • Create an IDE launcher for a Java Application
  • Set dev.jeka.tool.Main as Java main class.
  • Set the same command line arguments as you would do for invoking from command line (Do not include jeka command).

Let KBeans cooperate

Generally KBeans interact with each other by declaring KBeans using KBean#load(MyBean.class) method as shown in this example.

When a KBean depends on another one, it's good to declare it as an instance field of the first bean, as this dependency will be mentioned in the auto-generated documentation and showed explicitly in IDE tool.

KBeans in Multi-Projects

In a multi-project, it's quite common that a KBean accesses a KBean instance from another project. You can achieve this in a statically typed way.

  • In master KBean, declare a field of type KBean (e.g. ´JkBean importedBuild;`). It doesn't have to be public.
  • Annotate it with @JkInjectProject mentioning the relative path of the imported project (e.g. `@JkInjectProject("../anotherModule")).
  • Execute jeka intellij#iml or jeka eclipse#files.
  • Redefine the declared type from KBean to the concrete type of imported KBean
  • Now, master KBean can access the imported KBean in a static typed way.
  • See example here.
  • Be mindful that the imported KBean must deal with file paths using KBean#getBaseDir in order for it to be safely executed from any working directory.

Bundled KBeans

There are a bunch of KBeans bundled within Jeka. Those KBeans are always present.


ProjectKBean provides a wrapper around a JkProject for building JVM-based projects. This KBean initialises a default sensitive project object and provides a classic method for building a project (compile, package in jar, publish ...)

This KBean proposes an extension point through its configure(JkProject) method. This way, other KBeans can modify the properties of the project to be built.


IntellijKBean provides methods for generating metadata files for IntelliJ IDE. The content of an iml file is computed according the JkProject object found in project KBean.

This KBean proposes an extension point through its configure methods in order to modify the resulting iml (e.g. using a module dependency instead of a library dependency).


ScaffoldjKBean provides methods for project directories and files to create a new Jeka project. Basically, it creates a project ready to create vanilla automation tasks.

This KBean offers an extension point in order for another KBean to augment the scaffolded structure. For example, executing jeka scaffold#run will create a basic Jeka project while jeka scaffold#run project# will create a project ready to build a JVM-based project.


GitKBean exposes some common git command combos. It can also auto-inject a version inferred from Git into project KBean.