/*
* Copyright 2002-2010 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.io.IOException;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.Stack;
import org.springframework.beans.factory.parsing.Location;
import org.springframework.beans.factory.parsing.Problem;
import org.springframework.beans.factory.parsing.ProblemReporter;
import org.springframework.core.type.AnnotationMetadata;
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.util.StringUtils;
/**
* Parses a {@link Configuration} class definition, populating a collection of
* {@link ConfigurationClass} objects (parsing a single Configuration class may result in
* any number of ConfigurationClass objects because one Configuration class may import
* another using the {@link Import} annotation).
*
* <p>This class helps separate the concern of parsing the structure of a Configuration
* class from the concern of registering BeanDefinition objects based on the
* content of that model.
*
* <p>This ASM-based implementation avoids reflection and eager class loading in order to
* interoperate effectively with lazy class loading in a Spring ApplicationContext.
*
* @author Chris Beams
* @author Juergen Hoeller
* @since 3.0
* @see ConfigurationClassBeanDefinitionReader
*/
class ConfigurationClassParser {
private final MetadataReaderFactory metadataReaderFactory;
private final ProblemReporter problemReporter;
private final Stack<ConfigurationClass> importStack = new ImportStack();
private final Set<ConfigurationClass> configurationClasses =
new LinkedHashSet<ConfigurationClass>();
/**
* Create a new {@link ConfigurationClassParser} instance that will be used
* to populate the set of configuration classes.
*/
public ConfigurationClassParser(MetadataReaderFactory metadataReaderFactory, ProblemReporter problemReporter) {
this.metadataReaderFactory = metadataReaderFactory;
this.problemReporter = problemReporter;
}
/**
* Parse the specified {@link Configuration @Configuration} class.
* @param className the name of the class to parse
* @param beanName may be null, but if populated represents the bean id
* (assumes that this configuration class was configured via XML)
*/
public void parse(String className, String beanName) throws IOException {
MetadataReader reader = this.metadataReaderFactory.getMetadataReader(className);
processConfigurationClass(new ConfigurationClass(reader, beanName));
}
/**
* Parse the specified {@link Configuration @Configuration} class.
* @param clazz the Class to parse
* @param beanName may be null, but if populated represents the bean id
* (assumes that this configuration class was configured via XML)
*/
public void parse(Class<?> clazz, String beanName) throws IOException {
processConfigurationClass(new ConfigurationClass(clazz, beanName));
}
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
AnnotationMetadata metadata = configClass.getMetadata();
while (metadata != null) {
doProcessConfigurationClass(configClass, metadata);
String superClassName = metadata.getSuperClassName();
if (superClassName != null && !Object.class.getName().equals(superClassName)) {
if (metadata instanceof StandardAnnotationMetadata) {
Class<?> clazz = ((StandardAnnotationMetadata) metadata).getIntrospectedClass();
metadata = new StandardAnnotationMetadata(clazz.getSuperclass());
}
else {
MetadataReader reader = this.metadataReaderFactory.getMetadataReader(superClassName);
metadata = reader.getAnnotationMetadata();
}
}
else {
metadata = null;
}
}
if (this.configurationClasses.contains(configClass) && configClass.getBeanName() != null) {
// Explicit bean definition found, probably replacing an import.
// Let's remove the old one and go with the new one.
this.configurationClasses.remove(configClass);
}
this.configurationClasses.add(configClass);
}
protected void doProcessConfigurationClass(ConfigurationClass configClass, AnnotationMetadata metadata) throws IOException {
if (metadata.isAnnotated(Import.class.getName())) {
processImport(configClass, (String[]) metadata.getAnnotationAttributes(Import.class.getName(), true).get("value"));
}
if (metadata.isAnnotated(ImportResource.class.getName())) {
String[] resources = (String[]) metadata.getAnnotationAttributes(ImportResource.class.getName()).get("value");
Class<?> readerClass = (Class<?>) metadata.getAnnotationAttributes(ImportResource.class.getName()).get("reader");
if (readerClass == null) {
throw new IllegalStateException("No reader class associated with imported resources: " +
StringUtils.arrayToCommaDelimitedString(resources));
}
for (String resource : resources) {
configClass.addImportedResource(resource, readerClass);
}
}
Set<MethodMetadata> beanMethods = metadata.getAnnotatedMethods(Bean.class.getName());
for (MethodMetadata beanMethod : beanMethods) {
configClass.addMethod(new ConfigurationClassMethod(beanMethod, configClass));
}
}
private void processImport(ConfigurationClass configClass, String[] classesToImport) throws IOException {
if (this.importStack.contains(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack, configClass.getMetadata()));
}
else {
this.importStack.push(configClass);
for (String classToImport : classesToImport) {
MetadataReader reader = this.metadataReaderFactory.getMetadataReader(classToImport);
processConfigurationClass(new ConfigurationClass(reader, null));
}
this.importStack.pop();
}
}
/**
* Validate each {@link ConfigurationClass} object.
* @see ConfigurationClass#validate
*/
public void validate() {
for (ConfigurationClass configClass : this.configurationClasses) {
configClass.validate(this.problemReporter);
}
}
public Set<ConfigurationClass> getConfigurationClasses() {
return this.configurationClasses;
}
@SuppressWarnings("serial")
private static class ImportStack extends Stack<ConfigurationClass> {
/**
* Simplified contains() implementation that tests to see if any {@link ConfigurationClass}
* exists within this stack that has the same name as <var>elem</var>. Elem must be of
* type ConfigurationClass.
*/
@Override
public boolean contains(Object elem) {
ConfigurationClass configClass = (ConfigurationClass) elem;
Comparator<ConfigurationClass> comparator = new Comparator<ConfigurationClass>() {
public int compare(ConfigurationClass first, ConfigurationClass second) {
return first.getMetadata().getClassName().equals(second.getMetadata().getClassName()) ? 0 : 1;
}
};
return (Collections.binarySearch(this, configClass, comparator) != -1);
}
/**
* Given a stack containing (in order)
* <ol>
* <li>com.acme.Foo</li>
* <li>com.acme.Bar</li>
* <li>com.acme.Baz</li>
* </ol>
* Returns "Foo->Bar->Baz". In the case of an empty stack, returns empty string.
*/
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
Iterator<ConfigurationClass> iterator = iterator();
while (iterator.hasNext()) {
builder.append(iterator.next().getSimpleName());
if (iterator.hasNext()) {
builder.append("->");
}
}
return builder.toString();
}
}
/**
* {@link Problem} registered upon detection of a circular {@link Import}.
*/
private static class CircularImportProblem extends Problem {
public CircularImportProblem(ConfigurationClass attemptedImport, Stack<ConfigurationClass> importStack, AnnotationMetadata metadata) {
super(String.format("A circular @Import has been detected: " +
"Illegal attempt by @Configuration class '%s' to import class '%s' as '%s' is " +
"already present in the current import stack [%s]",
importStack.peek().getSimpleName(), attemptedImport.getSimpleName(),
attemptedImport.getSimpleName(), importStack),
new Location(importStack.peek().getResource(), metadata)
);
}
}
}
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