Choose an implementation at startup without changing the consuming class.
Open this stage in the online learning path
Use JDK 21 or newer and Maven 3.9 or newer. Verify with java -version and mvn -version. Extract this project into its own folder; do not merge its files with another stage.
This lesson reuses the product catalog and Todo responsibilities from Stages 8–14. Only the feature described below is new. Read the ordered explanation before opening the complete files.
CatalogSource describes the one operation the lesson needs. The two @Bean methods provide alternate implementations, with no database required yet.
The JVM system property spring.profiles.active selects dev or prod before context refresh. @Profile controls whether each factory method contributes its bean definition.
With neither profile active, Lesson cannot receive CatalogSource. With both active, two candidates exist. Select one profile for this example. Profiles can also select configuration classes and components.
Boot also supports application-dev.properties and application-prod.properties for profile-specific values. A profile is a configuration selector, not an authorization or security boundary.
Open a terminal in the extracted folder containing pom.xml. Run one command at a time.
mvn test
mvn spring-boot:run "-Dspring-boot.run.jvmArguments=-Dspring.profiles.active=dev"
mvn spring-boot:run "-Dspring-boot.run.jvmArguments=-Dspring.profiles.active=prod"This is a console lesson. It does not open a web port. Application.main starts a Spring context, calls the demonstration and closes the context. Read the terminal, not a browser. Spring Boot’s Maven plugin is used as a convenient launcher; these examples show Spring Framework directly.
With dev: Sample products
With prod: Production catalog selectedObject identifiers and elapsed times can vary. Compare the relationship between values rather than copying an identifier.
Create the following files at exactly these paths, or use the ZIP. Source files include their imports. The test checks the behaviour described in the lesson.
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>4.1.1</version><relativePath/></parent>
<groupId>com.edupoly</groupId><artifactId>spring-stage-26-profiles</artifactId><version>1.0.0</version>
<properties><java.version>21</java.version></properties>
<dependencies>
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency>
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency>
</dependencies>
<build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build>
</project>
package com.edupoly.lesson;
import org.springframework.context.annotation.*;
@Configuration @Import(Lesson.class)
public class AppConfig {
@Bean @Profile("dev") public CatalogSource developmentSource() { return () -> "Sample products"; }
@Bean @Profile("prod") public CatalogSource productionSource() { return () -> "Production catalog selected"; }
}
package com.edupoly.lesson;
public interface CatalogSource { String description(); }
package com.edupoly.lesson;
public class Lesson {
private final CatalogSource source;
public Lesson(CatalogSource source) { this.source = source; }
public void run() { System.out.println(source.description()); }
}
package com.edupoly.lesson;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Application {
public static void main(String[] args) throws Exception {
try (var context = new AnnotationConfigApplicationContext(AppConfig.class)) {
context.getBean(Lesson.class).run();
}
}
}
package com.edupoly.lesson;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
class LessonTest {
@Test void eachProfileSelectsOneImplementation() {
for (String profile : new String[]{"dev", "prod"}) {
try (var context = new AnnotationConfigApplicationContext()) {
context.getEnvironment().setActiveProfiles(profile); context.register(AppConfig.class); context.refresh();
assertEquals(1, context.getBeansOfType(CatalogSource.class).size());
assertEquals(profile.equals("dev") ? "Sample products" : "Production catalog selected", context.getBean(CatalogSource.class).description());
}
}
}
}
Run with neither profile. Read the missing CatalogSource dependency error. Then activate dev. Do not activate both dev and prod together in this example.
| Word | Meaning in this example |
|---|---|
| @Profile | Conditionally registers a bean for an active environment profile. |
| Active profile | The startup selection dev or prod. |
Add a test profile returning Test products, activate it and verify the output.