Springboot 101 : Auto Configuration

When it comes to Java development, convention and simplicity are greatly prized over configuration. Let me introduce you to Spring Boot, a framework that takes these ideas a step further with its robust auto-configuration capability. We’ll explore the inner workings of Spring Boot’s auto-configuration in this brief post and see how it streamlines the development process.

What is AutoConfiguration?

Fundamentally, the auto-configuration feature of Spring Boot sets up the Spring application context automatically by using the libraries on the classpath. The days of complex XML setups are over; Spring Boot determines the dependencies for your project and sets up the application appropriately. The auto-configuration process is initiated by the @EnableAutoConfiguration annotation, which orchestrates this magic.

How it Works ?

When you launch your Spring Boot application, it searches the classpath for specific conditions or markers. The presence of specific libraries, beans, or attributes is one of these identifiers. The application context is then configured by Spring Boot by producing beans that match the conditions. This allows developers to focus on defining business logic rather than laborious setup concerns.

For example , consider a scenario where your Spring Boot project includes the H2 database library in it’s classpath. Spring Boot’s auto-configuration, through conditional checks, will automatically configure a data source bean for H2. You can leverage this database without writing explicit configuration files.

// No need for explicit DataSource configuration
@SpringBootApplication
public class MySpringBootApplication {
    public static void main(String[] args) {
        SpringApplication.run(MySpringBootApplication.class, args);
    }
}

Customised Configuration

While the auto-configuration of Spring Boot is powerful out of the box, developers frequently need to customise it to fit unique requirements. This can be accomplished by adding @Configuration annotations to configuration classes. These classes have the ability to individually modify or supplement the default auto-configuration. This allows developers to keep the benefits of auto-configuration while adapting the application to their own needs.

For Example, Lets say we want to use our custom cache manager instead of using auto configured one. This @Configuration will allow user to definde their own custom configurations etc.

@Configuration
public class CustomCacheConfiguration {

    @Bean
    public CacheManager cacheManager() {
        // Custom cache manager configuration
        return new MyCustomCacheManager();
    }
}

Conditional Configuration

Springboot allows user to put conditional plugging / configuring options. The elegance of Spring Boot’s auto-configuration is found in its conditional annotations. Developers can use annotations like

1. @ConditionalOnClass
2. @ConditionalOnProperty
3. @ConditionalOnMissingBean

……. etc.

to fine-tune when specific configurations should take effect.

@Configuration
@ConditionalOnProperty(name = "myapp.feature.enabled", havingValue = "true")
public class MyFeatureConfiguration {
    // Bean configuration for the feature
}

Such kind of configuration gives developer a great flexibility over how and when you want to use ready to use configurable components.

Also there are lots of options but thats not feasible to write everything here otherwise its as good as official documentation.

Advantages of Auto-Configuration for Spring Boot:

1. Decreased Boilerplate Code:

Instead of wasting time on tedious configuration procedures, developers may concentrate on building business logic.

2. Convention Over Configuration:

Development and maintainability are accelerated by the framework’s sensible defaults and conventions.

Have fun exploring ….