Activate Maven Profile by Operating System

Who would have thought that you can develop a command line application with Spring? Since Spring Boot 3 has a support for building native executables, it has become not only possible but also a reasonable choice! Let's dive into how to do it step by step.

Create a new Spring Boot project

• use GraalVM distrubution of Java
• select "Picocli" in the dependency list

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootPicocliSampleApplication {

    public static void main(String[] args) {
        System.exit(SpringApplication.exit(SpringApplication.run(SpringBootPicocliSampleApplication.class, args)));
    }
}

import java.util.concurrent.Callable;

import picocli.CommandLine.Command;

import org.springframework.stereotype.Component;

@Component
@Command
public class MainCommand implements Callable<Integer> {
    @Override 
    public Integer call() {
        System.out.println("Hello from the main command");
        return 0;
    }
}

import picocli.CommandLine;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.ExitCodeGenerator;
import org.springframework.stereotype.Component;

@Component
public class PicoCommandLineRunner implements CommandLineRunner, ExitCodeGenerator {

    private final MainCommand mainCommand;

    private final CommandLine.IFactory factory;

    private int exitCode;

    public PicoCommandLineRunner(MainCommand mainCommand, CommandLine.IFactory factory) {
        this.mainCommand = mainCommand;
        this.factory = factory;
    }

    @Override
    public void run(String... args) {
        exitCode = new CommandLine(mainCommand, factory).execute(args);
    }

    @Override
    public int getExitCode() {
        return exitCode;
    }
}

Run with:

$ ./mvnw package
$ java -jar target/spring-boot-picocli-sample-0.0.1-SNAPSHOT.jar

Build to native:

...

Add options:

@Component
@Command
public class MainCommand implements Callable<Integer> {

    @CommandLine.Option(names = "--name", required = true)
    private String name;

    @Override public Integer call() {
        System.out.println("Hello %s from the main command".formatted(name));
        return 0;
    }
}

Add parameters:

@CommandLine.Parameters(index = "0", defaultValue = "0")
private int times;

@Option and @Parameters annotation can be placed either on field or on a setter method. in native image it must be on the field.

Add help command

@Command(subcommands = CommandLine.HelpCommand.class)
public class MainCommand implements Callable<Integer> {
    // ...
}

or

@Command(mixinStandardHelpOptions = true) // adds help and version

get rid of the default logging

logging.level.root=error

create custom banner

Ascii Banner Generator

and paste it into src/main/resources/banner.txt

banner colors

you can use ${AnsiColor.BLUE} etc

remember to set to default at the end

${AnsiColor.DEFAULT}.

remove the banner

spring.main.banner-mode=off

Add version command

normally version could be read from the manifest but it's not possible with current status of spring native

1. Add property to proeprties in pom.xml

<app.version>${project.version}</app.version>

2. Generate version.properties file during the build:

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>properties-maven-plugin</artifactId>
    <version>1.1.0</version>
    <executions>
        <execution>
            <phase>generate-resources</phase>
            <goals>
                <goal>write-project-properties</goal>
            </goals>
            <configuration>
                <outputFile>${project.build.outputDirectory}/version.properties</outputFile>
            </configuration>
        </execution>
    </executions>
</plugin>