Command Mode with Picocli
Picocli is an open source tool for creating rich command line applications.
Quarkus provides support for using Picocli. This guide contains examples of picocli
extension usage.
If you are not familiar with the Quarkus Command Mode, consider reading the Command Mode reference guide first. |
Extension
Once you have your Quarkus project configured you can add the picocli
extension
to your project by running the following command in your project base directory.
quarkus extension add picocli
./mvnw quarkus:add-extension -Dextensions='picocli'
./gradlew addExtension --extensions='picocli'
This will add the following to your build file:
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-picocli</artifactId>
</dependency>
implementation("io.quarkus:quarkus-picocli")
Building a command line application
Simple application
A simple Picocli application with only one Command
can be created as follows:
package com.acme.picocli;
import picocli.CommandLine;
import jakarta.enterprise.context.Dependent;
import jakarta.inject.Inject;
@CommandLine.Command (1)
public class HelloCommand implements Runnable {
@CommandLine.Option(names = {"-n", "--name"}, description = "Who will we greet?", defaultValue = "World")
String name;
private final GreetingService greetingService;
public HelloCommand(GreetingService greetingService) { (2)
this.greetingService = greetingService;
}
@Override
public void run() {
greetingService.sayHello(name);
}
}
@Dependent
class GreetingService {
void sayHello(String name) {
System.out.println("Hello " + name + "!");
}
}
1 | If there is only one class annotated with picocli.CommandLine.Command , it will be used automatically as the entry point of the command line application. |
2 | All classes annotated with picocli.CommandLine.Command are registered as CDI beans. |
Beans annotated with @CommandLine.Command should not use proxied scopes (e.g. do not use @ApplicationScoped )
because Picocli will not be able to set field values in such beans.
By default, this Picocli extension registers classes annotated with @CommandLine.Command
with the @Dependent scope. If you need to use a proxied scope, then annotate the setters and not the fields, for example:
|
@CommandLine.Command
@ApplicationScoped
public class EntryCommand {
private String name;
@CommandLine.Option(names = "-n")
public void setName(String name) {
this.name = name;
}
}
Command line application with multiple Commands
When multiple classes have the picocli.CommandLine.Command
annotation, then one of them needs to be also annotated with io.quarkus.picocli.runtime.annotations.TopCommand
.
This can be overwritten with the quarkus.picocli.top-command
property.
package com.acme.picocli;
import io.quarkus.picocli.runtime.annotations.TopCommand;
import picocli.CommandLine;
@TopCommand
@CommandLine.Command(mixinStandardHelpOptions = true, subcommands = {HelloCommand.class, GoodByeCommand.class})
public class EntryCommand {
}
@CommandLine.Command(name = "hello", description = "Greet World!")
class HelloCommand implements Runnable {
@Override
public void run() {
System.out.println("Hello World!");
}
}
@CommandLine.Command(name = "goodbye", description = "Say goodbye to World!")
class GoodByeCommand implements Runnable {
@Override
public void run() {
System.out.println("Goodbye World!");
}
}
Customizing Picocli CommandLine instance
You can customize CommandLine classes used by the picocli
extension by producing your own bean instance:
package com.acme.picocli;
import io.quarkus.picocli.runtime.PicocliCommandLineFactory;
import io.quarkus.picocli.runtime.annotations.TopCommand;
import picocli.CommandLine;
import jakarta.enterprise.context.ApplicationScoped;
import jakarta.enterprise.inject.Produces;
@TopCommand
@CommandLine.Command
public class EntryCommand implements Runnable {
@CommandLine.Spec
CommandLine.Model.CommandSpec spec;
@Override
public void run() {
System.out.println("My name is: " + spec.name());
}
}
@ApplicationScoped
class CustomConfiguration {
@Produces
CommandLine customCommandLine(PicocliCommandLineFactory factory) { (1)
return factory.create().setCommandName("CustomizedName");
}
}
1 | PicocliCommandLineFactory will create an instance of CommandLine with TopCommand and CommandLine.IFactory injected. |
Different entry command for each profile
It is possible to create different entry command for each profile, using @IfBuildProfile
:
@ApplicationScoped
public class Config {
@Produces
@TopCommand
@IfBuildProfile("dev")
public Object devCommand() {
return DevCommand.class; (1)
}
@Produces
@TopCommand
@IfBuildProfile("prod")
public Object prodCommand() {
return new ProdCommand("Configured by me!");
}
}
1 | You can return instance of java.lang.Class here. In such case CommandLine will try to instantiate this class using CommandLine.IFactory . |
Configure CDI Beans with parsed arguments
You can use Event<CommandLine.ParseResult>
or just CommandLine.ParseResult
to configure CDI beans based on arguments parsed by Picocli.
This event will be generated in QuarkusApplication
class created by this extension. If you are providing your own @QuarkusMain
this event will not be raised.
CommandLine.ParseResult
is created from default CommandLine
bean.
@CommandLine.Command
public class EntryCommand implements Runnable {
@CommandLine.Option(names = "-c", description = "JDBC connection string")
String connectionString;
@Inject
DataSource dataSource;
@Override
public void run() {
try (Connection c = dataSource.getConnection()) {
// Do something
} catch (SQLException throwables) {
// Handle error
}
}
}
@ApplicationScoped
class DatasourceConfiguration {
@Produces
@ApplicationScoped (1)
DataSource dataSource(CommandLine.ParseResult parseResult) {
PGSimpleDataSource ds = new PGSimpleDataSource();
ds.setURL(parseResult.matchedOption("c").getValue().toString());
return ds;
}
}
1 | @ApplicationScoped used for lazy initialization |
Providing your own QuarkusMain
You can also provide your own application entry point annotated with QuarkusMain
(as described in Command Mode reference guide).
package com.acme.picocli;
import io.quarkus.runtime.QuarkusApplication;
import io.quarkus.runtime.annotations.QuarkusMain;
import picocli.CommandLine;
import jakarta.inject.Inject;
@QuarkusMain
@CommandLine.Command(name = "demo", mixinStandardHelpOptions = true)
public class ExampleApp implements Runnable, QuarkusApplication {
@Inject
CommandLine.IFactory factory; (1)
@Override
public void run() {
// business logic
}
@Override
public int run(String... args) throws Exception {
return new CommandLine(this, factory).execute(args);
}
}
1 | Quarkus-compatible CommandLine.IFactory bean created by picocli extension. |
Development Mode
In the development mode, i.e. when running mvn quarkus:dev
, the application is executed and restarted every time the Space bar
key is pressed. You can also pass arguments to your command line app via the quarkus.args
system property, e.g. mvn quarkus:dev -Dquarkus.args='--help'
and mvn quarkus:dev -Dquarkus.args='-c -w --val 1'
.
For Gradle projects, arguments can be passed using --quarkus-args
.
If you’re creating a typical Quarkus application (e.g., HTTP-based services) that includes command-line functionality, you’ll need to handle the application’s lifecycle differently. In the |
Packaging your application
A Picocli command line application can be packaged in multiple formats (e.g. a JAR, a native executable) and can be published to various repositories (e.g. Homebrew, Chocolatey, SDKMAN!).
As a jar
A Picocli command line application is a standard Quarkus application and as such can be published as a JAR in various packaging formats (e.g. fast-jar, uber-jar).
In the context of a command line application, building an uber-jar is more practical if you plan on publishing the JAR as is.
For more information about how to build an uber-jar, see our documentation:
You can then execute the application by using the standard java -jar your-application.jar
command.
Using plugins such as the really-executable-jar-maven-plugin can be handy to simplify the execution of your command line application.
As a native executable
You can also build a native executable but keep in mind that native executables are not portable and that you need one binary per supported platform.
Publishing the application
Publishing your command line application to a repository makes it a lot easier to consume. Various application repositories are available depending on your requirements such as SDKMAN!, Homebrew for macOS, or Chocolatey for Windows.
To publish to these repositories, we recommend the usage of JReleaser.
JReleaser adds executable wrappers around your JAR for your application to be easily executable.
More information
You can also consult the Picocli official documentation for more general information about how to package Picocli applications.
Kubernetes support
Once you have your command line application, you can also generate the resources necessary to install and use this application in Kubernetes by adding the kubernetes
extension. To install the kubernetes
extension, run the following command in your project base directory.
quarkus extension add kubernetes
./mvnw quarkus:add-extension -Dextensions='kubernetes'
./gradlew addExtension --extensions='kubernetes'
This will add the following to your pom.xml
:
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-kubernetes</artifactId>
</dependency>
And, next, build the application with:
quarkus build
./mvnw install
./gradlew build
The Kubernetes extension will detect the presence of the Picocli extension and hence generate a Job resource instead of a Deployment resource in the target/kubernetes/
directory.
If you don’t want to generate a Job resource, you can specify the resource you want to generate using the property quarkus.kubernetes.deployment-kind . For example, if you want to generate a Deployment resource, use quarkus.kubernetes.deployment-kind=Deployment .
|
Moreover, you can provide the arguments that will be used by the Kubernetes job via the property quarkus.kubernetes.arguments
. For example, after adding the property quarkus.kubernetes.arguments=A,B
and building your project, the following Job resource will be generated:
apiVersion: batch/v1
kind: Job
metadata:
labels:
app.kubernetes.io/name: app
app.kubernetes.io/version: 0.1-SNAPSHOT
name: app
spec:
completionMode: NonIndexed
suspend: false
template:
metadata:
labels:
app.kubernetes.io/name: app
app.kubernetes.io/version: 0.1-SNAPSHOT
spec:
containers:
- args:
- A
- B
env:
- name: KUBERNETES_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
image: docker.io/user/app:0.1-SNAPSHOT
imagePullPolicy: Always
name: app
ports:
- containerPort: 8080
name: http
protocol: TCP
restartPolicy: OnFailure
terminationGracePeriodSeconds: 10
Finally, the Kubernetes job will be launched every time it is installed in Kubernetes. You can know more about how to run Kubernetes jobs in this document.
Configuration Reference
Configuration property fixed at build time - All other configuration properties are overridable at runtime
Configuration property |
Type |
Default |
||
---|---|---|---|---|
Set this to false to use the
This property is intended to be used only in cases where an incompatible change in the picocli library causes problems in the build steps used to support GraalVM Native images. In such cases this property allows users to make the trade-off between fast build cycles with the older version of picocli, and temporarily accept slower build cycles with the latest version of picocli until the updated extension is available. Environment variable: Show more |
boolean |
|
||
Name of bean annotated with Environment variable: Show more |
string |