spring-context中@ImportSource注解的说明

/**
 * Indicates one or more resources containing bean definitions to import.
 *
 * <p>Like {@link Import @Import}, this annotation provides functionality similar to
 * the {@code <import/>} element in Spring XML. It is typically used when designing
 * {@link Configuration @Configuration} classes to be bootstrapped by an
 * {@link AnnotationConfigApplicationContext}, but where some XML functionality such
 * as namespaces is still necessary.
 *
 * <p>By default, arguments to the {@link #value} attribute will be processed using a
 * {@link org.springframework.beans.factory.groovy.GroovyBeanDefinitionReader GroovyBeanDefinitionReader}
 * if ending in {@code ".groovy"}; otherwise, an
 * {@link org.springframework.beans.factory.xml.XmlBeanDefinitionReader XmlBeanDefinitionReader}
 * will be used to parse Spring {@code <beans/>} XML files. Optionally, the {@link #reader}
 * attribute may be declared, allowing the user to choose a custom {@link BeanDefinitionReader}
 * implementation.
 *
 * @author Chris Beams
 * @author Juergen Hoeller
 * @author Sam Brannen
 * @since 3.0
 * @see Configuration
 * @see Import
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})//只能标注在类上
@Documented
public @interface ImportResource {
    @AliasFor("locations")
    String[] value() default {};
    
    /**
     * Resource locations from which to import.
     * <p>Supports resource-loading prefixes such as {@code classpath:},
     * {@code file:}, etc.
     * <p>Consult the Javadoc for {@link #reader} for details on how resources
     * will be processed.
     * @since 4.2
     * @see #value
     * @see #reader
     */
    @AliasFor("value")
    String[] locations() default {};
    /**
     * {@link BeanDefinitionReader} implementation to use when processing
     * resources specified via the {@link #value} attribute.
     * <p>By default, the reader will be adapted to the resource path specified:
     * {@code ".groovy"} files will be processed with a
     * {@link org.springframework.beans.factory.groovy.GroovyBeanDefinitionReader GroovyBeanDefinitionReader};
     * whereas, all other resources will be processed with an
     * {@link org.springframework.beans.factory.xml.XmlBeanDefinitionReader XmlBeanDefinitionReader}.
     * @see #value
     */
    Class<? extends BeanDefinitionReader> reader() default BeanDefinitionReader.class;
}