1.概念
有2个特点
- 继承该接口的ImportSelector会在最后执行
- 如果定义了1一个以上的DeferredImportSelector则使用Order接口来进行排序
/**
* A variation of {@link ImportSelector} that runs after all {@code @Configuration} beans
* have been processed. This type of selector can be particularly useful when the selected
* imports are {@code @Conditional}.
*
* <p>Implementations can also extend the {@link org.springframework.core.Ordered}
* interface or use the {@link org.springframework.core.annotation.Order} annotation to
* indicate a precedence against other {@link DeferredImportSelector}s.
*
* @author Phillip Webb
* @since 4.0
*/
public interface DeferredImportSelector extends ImportSelector {
}
2.测试代码
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import({DeferredImportSelector1.class, DeferredImportSelector2.class, ImportSelector1.class, ImportSelector2.class})
public static @interface Sample {
}
public static class ImportSelector1 implements ImportSelector {
@Override
public String[] selectImports(AnnotationMetadata importingClassMetadata) {
ImportSelectorTests.importFrom.put(getClass(), importingClassMetadata.getClassName());
return new String[] { ImportedSelector1.class.getName() };
}
}
public static class ImportSelector2 implements ImportSelector {
@Override
public String[] selectImports(AnnotationMetadata importingClassMetadata) {
ImportSelectorTests.importFrom.put(getClass(), importingClassMetadata.getClassName());
return new String[] { ImportedSelector2.class.getName() };
}
}
public static class DeferredImportSelector1 implements DeferredImportSelector, Ordered {
@Override
public String[] selectImports(AnnotationMetadata importingClassMetadata) {
ImportSelectorTests.importFrom.put(getClass(), importingClassMetadata.getClassName());
return new String[] { DeferredImportedSelector1.class.getName() };
}
@Override
public int getOrder() {
return Ordered.LOWEST_PRECEDENCE;
}
}
@Order(Ordered.HIGHEST_PRECEDENCE)
public static class DeferredImportSelector2 implements DeferredImportSelector {
@Override
public String[] selectImports(AnnotationMetadata importingClassMetadata) {
ImportSelectorTests.importFrom.put(getClass(), importingClassMetadata.getClassName());
return new String[] { DeferredImportedSelector2.class.getName() };
}
}
执行的先后顺序为
ImportSelector1-> ImportSelector2-> DeferredImportSelector2-> DeferredImportSelector1
