Spring XML Bean Config vs Annotation-Driven
Replace verbose Spring XML bean definitions with concise annotation-driven configuration in Spring Boot.
<!-- applicationContext.xml -->
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="userRepository"
class="com.example.UserRepository">
<property name="dataSource" ref="dataSource"/>
</bean>
<bean id="userService"
class="com.example.UserService">
<property name="repository" ref="userRepository"/>
</bean>
</beans>
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
@Repository
public class UserRepository {
private final JdbcTemplate jdbc;
public UserRepository(JdbcTemplate jdbc) {
this.jdbc = jdbc;
}
}
@Service
public class UserService {
private final UserRepository repository;
public UserService(UserRepository repository) {
this.repository = repository;
}
}
No XML
@SpringBootApplication triggers component scanning and auto-configuration, eliminating all XML wiring files.
Constructor injection
Spring injects dependencies through constructors automatically, making beans easier to test and reason about.
Auto-configuration
Spring Boot configures DataSource, JPA, and other infrastructure from the classpath with zero boilerplate.
Widely available since Spring Boot 1.0 (April 2014); Spring Boot 3 requires Java 17+
Traditional Spring applications wired beans through XML configuration files, declaring each class and its dependencies as verbose <bean> elements. While annotation support existed since Spring 2.5, XML remained the dominant approach until Spring Boot introduced auto-configuration. Spring Boot detects beans annotated with @Component, @Service, @Repository, and @Controller via classpath scanning, satisfies dependencies through constructor injection automatically, and configures infrastructure like DataSource from the classpath โ eliminating all XML wiring files.