Spring Boot @Import and @ImportResource Examples

Learn to reuse an existing configuration in a Spring Boot application using the @Import and @ImportResource annotation with examples.

To import an existing configuration, add the @Import or @ImportResource annotation to your @Configuration or @SpringBootApplication annotated class.

1. Reusing an Existing Java Configuration with @Import Annotation

The @Import annotation is used to import additional Java-based configuration classes into the application context. This is useful when you want to modularize configuration and reuse existing configuration classes across multiple applications.

Let’s say we have a configuration class DatabaseConfig that configures the data source for our application:

@Configuration
public class DatabaseConfig {
    
    @Bean
    public DataSource dataSource() {

        // DataSource configuration
    }
}

We can import this configuration class into another configuration class using the @Import annotation:

@Configuration
@Import(DatabaseConfig.class)
public class AppConfig {

    // Bean definitions and other configurations
}

In this example, the DatabaseConfig configuration class is imported into the AppConfig configuration class using @Import. The beans defined in DatabaseConfig are now available in the application context.

To import multiple configuration classes, we can add all classes as an array of file paths in the annotation:

@Configuration
@Import({DatabaseConfig.class, SecurityConfig.class, MessagingConfig.class})
public class AppConfig {

    // Bean definitions and other configurations
}

2. Reusing an Existing XML Configuration with @ImportResource Annotation

The @ImportResource annotation is used to import XML-based configuration files into the application context. This is useful when you have existing XML configuration files that you want to integrate with Spring Boot applications.

Let’s say we have an XML configuration file legacy-beans.xml that defines some beans:

<beans>
    <bean id="legacyBean" class="com.example.LegacyBean"/>
</beans>

We can import this XML configuration file into a configuration class using the @ImportResource annotation:

@Configuration
@ImportResource("classpath:legacy-beans.xml")
public class XmlConfig {
    // Bean definitions and other configurations
}

In this example, the legacy-beans.xml file is imported into the XmlConfig configuration class using @ImportResource. The beans defined in the XML file are now available in the application context.

To import multiple XML configuration files, specify the names in the annotation as an array of file paths as follows:

@Configuration
@ImportResource({"classpath:legacy-beans1.xml", "classpath:legacy-beans2.xml"})
public class XmlConfig {

    // Bean definitions and other configurations
}

3. Conclusion

The @Import and @ImportResource annotations are powerful tools for organizing and modularizing configuration in Spring Boot applications. By leveraging @Import and @ImportResource, you can create more modular, maintainable, and flexible Spring Boot applications. You can experiment with these annotations in your projects to see how they can simplify your configuration management.

Happy Learning !!