001/* 002 * Copyright 2002-2020 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.context.annotation; 018 019import java.util.function.Predicate; 020 021import org.springframework.core.type.AnnotationMetadata; 022import org.springframework.lang.Nullable; 023 024/** 025 * Interface to be implemented by types that determine which @{@link Configuration} 026 * class(es) should be imported based on a given selection criteria, usually one or 027 * more annotation attributes. 028 * 029 * <p>An {@link ImportSelector} may implement any of the following 030 * {@link org.springframework.beans.factory.Aware Aware} interfaces, 031 * and their respective methods will be called prior to {@link #selectImports}: 032 * <ul> 033 * <li>{@link org.springframework.context.EnvironmentAware EnvironmentAware}</li> 034 * <li>{@link org.springframework.beans.factory.BeanFactoryAware BeanFactoryAware}</li> 035 * <li>{@link org.springframework.beans.factory.BeanClassLoaderAware BeanClassLoaderAware}</li> 036 * <li>{@link org.springframework.context.ResourceLoaderAware ResourceLoaderAware}</li> 037 * </ul> 038 * 039 * <p>Alternatively, the class may provide a single constructor with one or more of 040 * the following supported parameter types: 041 * <ul> 042 * <li>{@link org.springframework.core.env.Environment Environment}</li> 043 * <li>{@link org.springframework.beans.factory.BeanFactory BeanFactory}</li> 044 * <li>{@link java.lang.ClassLoader ClassLoader}</li> 045 * <li>{@link org.springframework.core.io.ResourceLoader ResourceLoader}</li> 046 * </ul> 047 * 048 * <p>{@code ImportSelector} implementations are usually processed in the same way 049 * as regular {@code @Import} annotations, however, it is also possible to defer 050 * selection of imports until all {@code @Configuration} classes have been processed 051 * (see {@link DeferredImportSelector} for details). 052 * 053 * @author Chris Beams 054 * @author Juergen Hoeller 055 * @since 3.1 056 * @see DeferredImportSelector 057 * @see Import 058 * @see ImportBeanDefinitionRegistrar 059 * @see Configuration 060 */ 061public interface ImportSelector { 062 063 /** 064 * Select and return the names of which class(es) should be imported based on 065 * the {@link AnnotationMetadata} of the importing @{@link Configuration} class. 066 * @return the class names, or an empty array if none 067 */ 068 String[] selectImports(AnnotationMetadata importingClassMetadata); 069 070 /** 071 * Return a predicate for excluding classes from the import candidates, to be 072 * transitively applied to all classes found through this selector's imports. 073 * <p>If this predicate returns {@code true} for a given fully-qualified 074 * class name, said class will not be considered as an imported configuration 075 * class, bypassing class file loading as well as metadata introspection. 076 * @return the filter predicate for fully-qualified candidate class names 077 * of transitively imported configuration classes, or {@code null} if none 078 * @since 5.2.4 079 */ 080 @Nullable 081 default Predicate<String> getExclusionFilter() { 082 return null; 083 } 084 085}