Stage 26: select a catalog source with a profile
Learning path / Stage 26 of 37
Choose an implementation at startup without changing the consuming class.
Download the complete Stage 26 project · Open the project guide
Before you start
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.
What we change and why
Keep one contract
CatalogSource describes the one operation the lesson needs. The two @Bean methods provide alternate implementations, with no database required yet.
Activate exactly one profile
The JVM system property spring.profiles.active selects dev or prod before context refresh. @Profile controls whether each factory method contributes its bean definition.
Observe a missing or ambiguous choice
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.
Connect profiles to properties
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.
Run this example
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.
Expected result
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.
Understand each complete file
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.
pom.xml
<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>
src/main/java/com/edupoly/lesson/AppConfig.java
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"; }
}
src/main/java/com/edupoly/lesson/CatalogSource.java
package com.edupoly.lesson;
public interface CatalogSource { String description(); }
src/main/java/com/edupoly/lesson/Lesson.java
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()); }
}
src/main/java/com/edupoly/lesson/Application.java
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();
}
}
}
src/test/java/com/edupoly/lesson/LessonTest.java
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());
}
}
}
}
Try a failure, then correct it
Run with neither profile. Read the missing CatalogSource dependency error. Then activate dev. Do not activate both dev and prod together in this example.
Words you can now explain
| Word | Meaning in this example |
|---|---|
| @Profile | Conditionally registers a bean for an active environment profile. |
| Active profile | The startup selection dev or prod. |
Practice assignment
Add a test profile returning Test products, activate it and verify the output.
Concepts used in this stage
Use the right column for a quick reminder, or open a concept above for its full explanation.