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Introduce ImportSelector interface 

Allows @Enable* a layer of indirection for deciding which @Configuration
class(es) to @Import.

The @Import annotation may now accept @Configuration class literals
and/or ImportSelector class literals.
This commit is contained in:
Chris Beams 2011-05-06 19:06:02 +00:00
parent cdb01cbd37
commit 9a271ce6c9
2 changed files with 62 additions and 7 deletions
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27
org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassParser.java
View File

@ -27,6 +27,7 @@ import java.util.Map;
import java.util.Set;
import java.util.Stack;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.parsing.Location;
import org.springframework.beans.factory.parsing.Problem;
import org.springframework.beans.factory.parsing.ProblemReporter;
@ -37,6 +38,7 @@ import org.springframework.core.type.MethodMetadata;
import org.springframework.core.type.StandardAnnotationMetadata;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.core.type.filter.AssignableTypeFilter;
import org.springframework.util.StringUtils;
/**
@ -142,7 +144,7 @@ class ConfigurationClassParser {
List<Map<String, Object>> allImportAttribs =
AnnotationUtils.findAllAnnotationAttributes(Import.class, metadata.getClassName(), true);
for (Map<String, Object> importAttribs : allImportAttribs) {
processImport(configClass, (String[]) importAttribs.get("value"));
processImport(configClass, (String[]) importAttribs.get("value"), true);
}
if (metadata.isAnnotated(ImportResource.class.getName())) {
@ -162,17 +164,30 @@ class ConfigurationClassParser {
}
}
private void processImport(ConfigurationClass configClass, String[] classesToImport) throws IOException {
if (this.importStack.contains(configClass)) {
private void processImport(ConfigurationClass configClass, String[] classesToImport, boolean checkForCircularImports) throws IOException {
if (checkForCircularImports && this.importStack.contains(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack, configClass.getMetadata()));
}
else {
this.importStack.push(configClass);
for (String classToImport : classesToImport) {
this.importStack.registerImport(configClass.getMetadata().getClassName(), classToImport);
MetadataReader reader = this.metadataReaderFactory.getMetadataReader(classToImport);
AnnotationMetadata importingClassMetadata = configClass.getMetadata();
for (String candidate : classesToImport) {
MetadataReader reader = this.metadataReaderFactory.getMetadataReader(candidate);
if (new AssignableTypeFilter(ImportSelector.class).match(reader, metadataReaderFactory)) {
// the candidate class is an ImportSelector -> delegate to it to determine imports
try {
ImportSelector selector = BeanUtils.instantiateClass(Class.forName(candidate), ImportSelector.class);
processImport(configClass, selector.selectImports(importingClassMetadata), false);
} catch (ClassNotFoundException ex) {
throw new IllegalStateException(ex);
}
}
else {
// the candidate class not an ImportSelector -> process it as a @Configuration class
this.importStack.registerImport(importingClassMetadata.getClassName(), candidate);
processConfigurationClass(new ConfigurationClass(reader, null));
}
}
this.importStack.pop();
}
}

40
org.springframework.context/src/main/java/org/springframework/context/annotation/ImportSelector.java Normal file
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@ -0,0 +1,40 @@
/*
* Copyright 2002-2011 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 org.springframework.core.type.AnnotationMetadata;
/**
* Interface to be implemented by types that determine
* which @{@link Configuration} class(es) should be imported based on
* a given selection criteria, usually an annotation attribute.
*
* @author Chris Beams
* @since 3.1
* @see Import
*/
public interface ImportSelector {
/**
* Select and return the names of which class(es) should be imported.
* @param importingClassMetadata the AnnotationMetodata of the
* importing @{@link Configuration} class.
*/
String[] selectImports(AnnotationMetadata importingClassMetadata);
}