In this article, we will discuss the @SpringBootApplication annotation. This is the core annotation under use while working on the Spring Boot applications.
Introduction
While working on the Spring application, we may use the following 3 annotation frequently.
@Configure@EnableAutoConfiguration@ComponentScan
These annotations are the most common while working on any Spring application as they are the building blocks. Based on their frequent use, Spring Boot provides a convenient @SpringBootApplication alternative.
1. The @SpringBootApplication
The @SpringBootApplication annotation is a convenience annotation equivalent to declaring @Configuration, @EnableAutoConfiguration and @ComponentScan. You can use this annotation in place of using above three different annotations. This is how we use it on our main Spring Boot class:
@SpringBootApplication
public class SpringMvcFileUploadApplication {
public static void main(String[] args) {
SpringApplication.run(SpringMvcFileUploadApplication.class, args);
}
}For simple Spring application, above code look like:
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = {
@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class)
})
public @interface SpringBootApplication {
@AliasFor(annotation = EnableAutoConfiguration.class)
Class <<?> [] exclude() default {};
@AliasFor(annotation = EnableAutoConfiguration.class)
String[] excludeName() default {};
@AliasFor(annotation = ComponentScan.class, attribute = "basePackages")
String[] scanBasePackages() default {};
@AliasFor(annotation = ComponentScan.class, attribute = "basePackageClasses")
Class <<?> [] scanBasePackageClasses() default {};
}
1.1 @Configuration Annotation
Indicates that a class declares one or more @Bean methods and use by the Spring container to generate bean definitions and service requests for those beans at run-time. This is important to support Java-based configuration over XML configuration.
1.2 @EnableAutoConfiguration
This enable the Spring Boot auto configuration feature.
1.3 @ComponentScan
This annotation enables a component-scanning so that the web controller classes and other components automatically discovered and registered as beans.
2. The @SpringBootApplication Parameters
The @SpringBootApplication annotation provides the option to customize its behaviour by passing additional parameters:
String[] excludeName– Exclude specific auto-configuration class names.String[] scanBasePackages– Base packages to scan for annotated components.Class<?>[] scanBasePackageClasses– Type-safe alternative to scanBasePackages for specifying the packages to scan for annotated components.Class<?>[] exclude– Exclude specific auto-configuration classes.
Summary
In this sort post, we cover the @SpringBootApplication annotation. We talk about the how this new annotation provide the flexibility and convenience in your Spring Boot application.
