Profiles and Property Sources

Profiles and Property Sources

Applications behave differently per environment: a dev setup uses H2 in memory, production uses a managed database and stricter logging. Spring addresses this with profiles for beans and property sources for configuration values.

Profiles gate beans

Annotate beans with @Profile("dev") and they exist only when that profile is active. Activate profiles with spring.profiles.active, a program argument, or the environment variable. You can also annotate entire @Configuration classes so a whole set of beans activates together.

@Configuration
@Profile("dev")
public class DevDataSourceConfig {
    @Bean
    public DataSource dataSource() {
        return new EmbeddedDatabaseBuilder()
                .setType(EmbeddedDatabaseType.H2)
                .build();
    }
}

Property sources

Spring collects configuration values from many sources: command-line arguments, environment variables, JVM system properties, profile-specific property files, and the base application.properties, in a well-defined precedence order. Later sources win. The Environment abstraction exposes all of it through a single API.

Comparing mechanisms

Think of @Value("${app.retry.count}") for individual values and @ConfigurationProperties for typed groups. Profiles change which beans and property files are active; property sources supply the values themselves. Together they let the same classes adapt to any environment.

Safe defaults

Only put environment-independent defaults in the base properties file, and read the rest from profiles or the environment. Secrets never belong in property files committed to a repository; resolve them from environment variables or a secret manager at runtime.

Key Points

• Profiles activate environment-specific beans and property files.
• Property sources follow a precedence order that later wins.
• Use @Profile on beans or configuration classes.
• Prefer @ConfigurationProperties for grouped configuration.
• Keep secrets out of property files; use environment sources.