org.springframework.context.annotation.AdviceModeImportSelector Maven / Gradle / Ivy
/*
* Copyright 2002-2018 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
*
* https://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;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* 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 annotation containing {@linkplain #getAdviceModeAttributeName() AdviceMode attribute}
*/
public abstract class AdviceModeImportSelector implements ImportSelector {
/**
* The default advice mode attribute name.
*/
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}.
* 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 annType = GenericTypeResolver.resolveTypeArgument(getClass(), AdviceModeImportSelector.class);
Assert.state(annType != null, "Unresolvable type argument for AdviceModeImportSelector");
AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(importingClassMetadata, annType);
if (attributes == null) {
throw new IllegalArgumentException(String.format(
"@%s is not present on importing class '%s' as expected",
annType.getSimpleName(), importingClassMetadata.getClassName()));
}
AdviceMode adviceMode = attributes.getEnum(getAdviceModeAttributeName());
String[] imports = selectImports(adviceMode);
if (imports == null) {
throw new IllegalArgumentException("Unknown AdviceMode: " + adviceMode);
}
return imports;
}
/**
* Determine which classes should be imported based on the given {@code AdviceMode}.
*
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)
*/
@Nullable
protected abstract String[] selectImports(AdviceMode adviceMode);
}