Command Line Arguments

# ── Application arguments (--) — highest priority in Spring Environment:
java -jar myapp.jar --server.port=9090 --spring.profiles.active=prod

# ── JVM system properties (-D) — lower priority than --args:
java -Dserver.port=9090 -Dspring.profiles.active=prod -jar myapp.jar

# ── Both together — --args override -D for the same key:
java -Dserver.port=8080 -jar myapp.jar --server.port=9090
# Result: server.port = 9090 (-- wins)

# ── JVM memory and tuning flags (not Spring properties):
java -Xms512m -Xmx2g -XX:+UseG1GC -jar myapp.jar

# ── Full production launch command combining both:
java \
  -Xms512m -Xmx2g \
  -XX:+UseG1GC \
  -Dfile.encoding=UTF-8 \
  -jar myapp.jar \
  --spring.profiles.active=prod \
  --server.port=8080 \
  --spring.datasource.url=jdbc:mysql://db:3306/mydb

# Override server port:
java -jar myapp.jar --server.port=9090

# Override datasource URL (useful for pointing at a different DB):
java -jar myapp.jar --spring.datasource.url=jdbc:mysql://localhost:3306/testdb

# Activate a profile:
java -jar myapp.jar --spring.profiles.active=prod

# Activate multiple profiles:
java -jar myapp.jar --spring.profiles.active=prod,metrics

# Override log level:
java -jar myapp.jar --logging.level.com.example=DEBUG

# Override any app.* custom property:
java -jar myapp.jar --app.jwt.expiration=3600 --app.features.payments=true

# Override Flyway migration behavior:
java -jar myapp.jar --spring.flyway.enabled=false

# Change context path:
java -jar myapp.jar --server.servlet.context-path=/v2

# Combine with env vars — --args still win:
export SERVER_PORT=8080
java -jar myapp.jar --server.port=9090   # 9090 wins

@Component
@RequiredArgsConstructor
public class ArgInspector implements ApplicationRunner {

    private final ApplicationArguments args;

    @Override
    public void run(ApplicationArguments arguments) {

        // All raw args as passed on the command line:
        String[] raw = arguments.getSourceArgs();
        // e.g. ["--server.port=9090", "--debug", "import", "users.csv"]

        // Option args — those prefixed with --:
        Set<String> optionNames = arguments.getOptionNames();
        // e.g. ["server.port", "debug"]

        boolean hasDebug = arguments.containsOption("debug");

        // Get values for a specific option (returns List<String>):
        List<String> ports = arguments.getOptionValues("server.port");
        // e.g. ["9090"]

        // Non-option args — bare values without --:
        List<String> nonOption = arguments.getNonOptionArgs();
        // e.g. ["import", "users.csv"]

        log.info("Option args: {}", optionNames);
        log.info("Non-option args: {}", nonOption);
    }
}

// NOTE: ApplicationArguments only sees the original --args.
// Properties overridden via --args are also in the Environment —
// inject Environment or @Value to read them as regular properties.

// ── CommandLineRunner — receives raw String[] args ────────────────────
@Component
@RequiredArgsConstructor
public class DataImportRunner implements CommandLineRunner {

    private final UserImportService importService;

    @Override
    public void run(String... args) throws Exception {
        // args = raw command-line strings, e.g. ["--mode=full", "users.csv"]
        for (String arg : args) {
            log.info("Arg: {}", arg);
        }
        importService.runStartupCheck();
    }
}

// ── ApplicationRunner — receives ApplicationArguments ────────────────
@Component
@RequiredArgsConstructor
public class MigrationRunner implements ApplicationRunner {

    private final MigrationService migrationService;

    @Override
    public void run(ApplicationArguments args) throws Exception {
        if (args.containsOption("migrate")) {
            List<String> targets = args.getOptionValues("migrate");
            // java -jar myapp.jar --migrate=v2 --migrate=v3
            targets.forEach(migrationService::run);
        }
    }
}

// ── Ordering multiple runners with @Order ─────────────────────────────
@Component
@Order(1)    // runs first
public class SchemaValidationRunner implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) {
        log.info("Validating schema...");
    }
}

@Component
@Order(2)    // runs second
public class SeedDataRunner implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) {
        log.info("Seeding reference data...");
    }
}

// Disable -- argument processing (they will no longer override properties):
@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(MyApplication.class);
        app.setAddCommandLineProperties(false);  // -- args ignored as properties
        app.run(args);
    }
}

// ApplicationArguments and CommandLineRunner still receive the raw args —
// only the auto-injection into the Spring Environment is disabled.
// Use this when you want to process args manually without allowing
// arbitrary property overrides from the command line.

# ── IntelliJ IDEA ─────────────────────────────────────────────────────
# Run/Debug Configurations → Modify options → Program arguments:
--spring.profiles.active=dev --server.port=9090 --app.features.payments=true

# VM options (for -D flags):
-Xmx512m -Dfile.encoding=UTF-8

# ── Maven ─────────────────────────────────────────────────────────────
mvn spring-boot:run -Dspring-boot.run.arguments="--server.port=9090 --spring.profiles.active=dev"

# Or with the spring-boot-maven-plugin in pom.xml:
<plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
  <configuration>
    <arguments>
      <argument>--server.port=9090</argument>
      <argument>--spring.profiles.active=dev</argument>
    </arguments>
  </configuration>
</plugin>

# ── Gradle ────────────────────────────────────────────────────────────
./gradlew bootRun --args='--server.port=9090 --spring.profiles.active=dev'

# ── Docker — ENTRYPOINT vs CMD for passing arguments ──────────────────
# Using CMD (arguments can be overridden at docker run):
FROM eclipse-temurin:21-jre
COPY target/myapp.jar app.jar
ENTRYPOINT ["java", "-jar", "/app.jar"]
CMD ["--spring.profiles.active=prod"]

# Override at runtime:
docker run myapp:latest --spring.profiles.active=dev --server.port=9090

# Using env vars instead (more idiomatic for containers):
docker run \
  -e SPRING_PROFILES_ACTIVE=prod \
  -e SERVER_PORT=8080 \
  myapp:latest