/*
* Copyright 2002-2015 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.context.annotation;
import java.lang.annotation.Annotation;
import org.springframework.core.GenericTypeResolver;
import org.springframework.core.annotation.AnnotationAttributes;
import org.springframework.core.type.AnnotationMetadata;
/**
* Convenient base class for {@link ImportSelector} implementations that select imports
* based on an {@link AdviceMode} value from an annotation (such as the {@code @Enable*}
* annotations).
*
* @author Chris Beams
* @since 3.1
* @param <A> annotation containing {@linkplain #getAdviceModeAttributeName() AdviceMode attribute}
*/
public abstract class AdviceModeImportSelector<A extends Annotation> implements ImportSelector {
public static final String DEFAULT_ADVICE_MODE_ATTRIBUTE_NAME = "mode";
/**
* The name of the {@link AdviceMode} attribute for the annotation specified by the
* generic type {@code A}. The default is {@value #DEFAULT_ADVICE_MODE_ATTRIBUTE_NAME},
* but subclasses may override in order to customize.
*/
protected String getAdviceModeAttributeName() {
return DEFAULT_ADVICE_MODE_ATTRIBUTE_NAME;
}
/**
* This implementation resolves the type of annotation from generic metadata and
* validates that (a) the annotation is in fact present on the importing
* {@code @Configuration} class and (b) that the given annotation has an
* {@linkplain #getAdviceModeAttributeName() advice mode attribute} of type
* {@link AdviceMode}.
* <p>The {@link #selectImports(AdviceMode)} method is then invoked, allowing the
* concrete implementation to choose imports in a safe and convenient fashion.
* @throws IllegalArgumentException if expected annotation {@code A} is not present
* on the importing {@code @Configuration} class or if {@link #selectImports(AdviceMode)}
* returns {@code null}
*/
@Override
public final String[] selectImports(AnnotationMetadata importingClassMetadata) {
Class<?> annoType = GenericTypeResolver.resolveTypeArgument(getClass(), AdviceModeImportSelector.class);
AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(importingClassMetadata, annoType);
if (attributes == null) {
throw new IllegalArgumentException(String.format(
"@%s is not present on importing class '%s' as expected",
annoType.getSimpleName(), importingClassMetadata.getClassName()));
}
AdviceMode adviceMode = attributes.getEnum(this.getAdviceModeAttributeName());
String[] imports = selectImports(adviceMode);
if (imports == null) {
throw new IllegalArgumentException(String.format("Unknown AdviceMode: '%s'", adviceMode));
}
return imports;
}
/**
* Determine which classes should be imported based on the given {@code AdviceMode}.
* <p>Returning {@code null} from this method indicates that the {@code AdviceMode} could
* not be handled or was unknown and that an {@code IllegalArgumentException} should
* be thrown.
* @param adviceMode the value of the {@linkplain #getAdviceModeAttributeName()
* advice mode attribute} for the annotation specified via generics.
* @return array containing classes to import; empty array if none, {@code null} if
* the given {@code AdviceMode} is unknown.
*/
protected abstract String[] selectImports(AdviceMode adviceMode);
}