spring QualifierAnnotationAutowireCandidateResolver 源码
spring QualifierAnnotationAutowireCandidateResolver 代码
文件路径：/spring-beans/src/main/java/org/springframework/beans/factory/annotation/QualifierAnnotationAutowireCandidateResolver.java
/*
* Copyright 2002-2020 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.beans.factory.annotation;
import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Method;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import org.springframework.beans.SimpleTypeConverter;
import org.springframework.beans.TypeConverter;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.config.DependencyDescriptor;
import org.springframework.beans.factory.support.AutowireCandidateQualifier;
import org.springframework.beans.factory.support.AutowireCandidateResolver;
import org.springframework.beans.factory.support.GenericTypeAwareAutowireCandidateResolver;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.core.MethodParameter;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.core.annotation.AnnotationAttributes;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;
/**
* {@link AutowireCandidateResolver} implementation that matches bean definition qualifiers
* against {@link Qualifier qualifier annotations} on the field or parameter to be autowired.
* Also supports suggested expression values through a {@link Value value} annotation.
*
* <p>Also supports JSR-330's {@link jakarta.inject.Qualifier} annotation, if available.
*
* @author Mark Fisher
* @author Juergen Hoeller
* @author Stephane Nicoll
* @since 2.5
* @see AutowireCandidateQualifier
* @see Qualifier
* @see Value
*/
public class QualifierAnnotationAutowireCandidateResolver extends GenericTypeAwareAutowireCandidateResolver {
private final Set<Class<? extends Annotation>> qualifierTypes = new LinkedHashSet<>(2);
private Class<? extends Annotation> valueAnnotationType = Value.class;
/**
* Create a new QualifierAnnotationAutowireCandidateResolver
* for Spring's standard {@link Qualifier} annotation.
* <p>Also supports JSR-330's {@link jakarta.inject.Qualifier} annotation, if available.
*/
@SuppressWarnings("unchecked")
public QualifierAnnotationAutowireCandidateResolver() {
this.qualifierTypes.add(Qualifier.class);
try {
this.qualifierTypes.add((Class<? extends Annotation>) ClassUtils.forName("jakarta.inject.Qualifier",
QualifierAnnotationAutowireCandidateResolver.class.getClassLoader()));
}
catch (ClassNotFoundException ex) {
// JSR-330 API not available - simply skip.
}
}
/**
* Create a new QualifierAnnotationAutowireCandidateResolver
* for the given qualifier annotation type.
* @param qualifierType the qualifier annotation to look for
*/
public QualifierAnnotationAutowireCandidateResolver(Class<? extends Annotation> qualifierType) {
Assert.notNull(qualifierType, "'qualifierType' must not be null");
this.qualifierTypes.add(qualifierType);
}
/**
* Create a new QualifierAnnotationAutowireCandidateResolver
* for the given qualifier annotation types.
* @param qualifierTypes the qualifier annotations to look for
*/
public QualifierAnnotationAutowireCandidateResolver(Set<Class<? extends Annotation>> qualifierTypes) {
Assert.notNull(qualifierTypes, "'qualifierTypes' must not be null");
this.qualifierTypes.addAll(qualifierTypes);
}
/**
* Register the given type to be used as a qualifier when autowiring.
* <p>This identifies qualifier annotations for direct use (on fields,
* method parameters and constructor parameters) as well as meta
* annotations that in turn identify actual qualifier annotations.
* <p>This implementation only supports annotations as qualifier types.
* The default is Spring's {@link Qualifier} annotation which serves
* as a qualifier for direct use and also as a meta annotation.
* @param qualifierType the annotation type to register
*/
public void addQualifierType(Class<? extends Annotation> qualifierType) {
this.qualifierTypes.add(qualifierType);
}
/**
* Set the 'value' annotation type, to be used on fields, method parameters
* and constructor parameters.
* <p>The default value annotation type is the Spring-provided
* {@link Value} annotation.
* <p>This setter property exists so that developers can provide their own
* (non-Spring-specific) annotation type to indicate a default value
* expression for a specific argument.
*/
public void setValueAnnotationType(Class<? extends Annotation> valueAnnotationType) {
this.valueAnnotationType = valueAnnotationType;
}
/**
* Determine whether the provided bean definition is an autowire candidate.
* <p>To be considered a candidate the bean's <em>autowire-candidate</em>
* attribute must not have been set to 'false'. Also, if an annotation on
* the field or parameter to be autowired is recognized by this bean factory
* as a <em>qualifier</em>, the bean must 'match' against the annotation as
* well as any attributes it may contain. The bean definition must contain
* the same qualifier or match by meta attributes. A "value" attribute will
* fall back to match against the bean name or an alias if a qualifier or
* attribute does not match.
* @see Qualifier
*/
@Override
public boolean isAutowireCandidate(BeanDefinitionHolder bdHolder, DependencyDescriptor descriptor) {
boolean match = super.isAutowireCandidate(bdHolder, descriptor);
if (match) {
match = checkQualifiers(bdHolder, descriptor.getAnnotations());
if (match) {
MethodParameter methodParam = descriptor.getMethodParameter();
if (methodParam != null) {
Method method = methodParam.getMethod();
if (method == null || void.class == method.getReturnType()) {
match = checkQualifiers(bdHolder, methodParam.getMethodAnnotations());
}
}
}
}
return match;
}
/**
* Match the given qualifier annotations against the candidate bean definition.
*/
protected boolean checkQualifiers(BeanDefinitionHolder bdHolder, Annotation[] annotationsToSearch) {
if (ObjectUtils.isEmpty(annotationsToSearch)) {
return true;
}
SimpleTypeConverter typeConverter = new SimpleTypeConverter();
for (Annotation annotation : annotationsToSearch) {
Class<? extends Annotation> type = annotation.annotationType();
boolean checkMeta = true;
boolean fallbackToMeta = false;
if (isQualifier(type)) {
if (!checkQualifier(bdHolder, annotation, typeConverter)) {
fallbackToMeta = true;
}
else {
checkMeta = false;
}
}
if (checkMeta) {
boolean foundMeta = false;
for (Annotation metaAnn : type.getAnnotations()) {
Class<? extends Annotation> metaType = metaAnn.annotationType();
if (isQualifier(metaType)) {
foundMeta = true;
// Only accept fallback match if @Qualifier annotation has a value...
// Otherwise, it is just a marker for a custom qualifier annotation.
if ((fallbackToMeta && ObjectUtils.isEmpty(AnnotationUtils.getValue(metaAnn))) ||
!checkQualifier(bdHolder, metaAnn, typeConverter)) {
return false;
}
}
}
if (fallbackToMeta && !foundMeta) {
return false;
}
}
}
return true;
}
/**
* Checks whether the given annotation type is a recognized qualifier type.
*/
protected boolean isQualifier(Class<? extends Annotation> annotationType) {
for (Class<? extends Annotation> qualifierType : this.qualifierTypes) {
if (annotationType.equals(qualifierType) || annotationType.isAnnotationPresent(qualifierType)) {
return true;
}
}
return false;
}
/**
* Match the given qualifier annotation against the candidate bean definition.
*/
protected boolean checkQualifier(
BeanDefinitionHolder bdHolder, Annotation annotation, TypeConverter typeConverter) {
Class<? extends Annotation> type = annotation.annotationType();
RootBeanDefinition bd = (RootBeanDefinition) bdHolder.getBeanDefinition();
AutowireCandidateQualifier qualifier = bd.getQualifier(type.getName());
if (qualifier == null) {
qualifier = bd.getQualifier(ClassUtils.getShortName(type));
}
if (qualifier == null) {
// First, check annotation on qualified element, if any
Annotation targetAnnotation = getQualifiedElementAnnotation(bd, type);
// Then, check annotation on factory method, if applicable
if (targetAnnotation == null) {
targetAnnotation = getFactoryMethodAnnotation(bd, type);
}
if (targetAnnotation == null) {
RootBeanDefinition dbd = getResolvedDecoratedDefinition(bd);
if (dbd != null) {
targetAnnotation = getFactoryMethodAnnotation(dbd, type);
}
}
if (targetAnnotation == null) {
// Look for matching annotation on the target class
if (getBeanFactory() != null) {
try {
Class<?> beanType = getBeanFactory().getType(bdHolder.getBeanName());
if (beanType != null) {
targetAnnotation = AnnotationUtils.getAnnotation(ClassUtils.getUserClass(beanType), type);
}
}
catch (NoSuchBeanDefinitionException ex) {
// Not the usual case - simply forget about the type check...
}
}
if (targetAnnotation == null && bd.hasBeanClass()) {
targetAnnotation = AnnotationUtils.getAnnotation(ClassUtils.getUserClass(bd.getBeanClass()), type);
}
}
if (targetAnnotation != null && targetAnnotation.equals(annotation)) {
return true;
}
}
Map<String, Object> attributes = AnnotationUtils.getAnnotationAttributes(annotation);
if (attributes.isEmpty() && qualifier == null) {
// If no attributes, the qualifier must be present
return false;
}
for (Map.Entry<String, Object> entry : attributes.entrySet()) {
String attributeName = entry.getKey();
Object expectedValue = entry.getValue();
Object actualValue = null;
// Check qualifier first
if (qualifier != null) {
actualValue = qualifier.getAttribute(attributeName);
}
if (actualValue == null) {
// Fall back on bean definition attribute
actualValue = bd.getAttribute(attributeName);
}
if (actualValue == null && attributeName.equals(AutowireCandidateQualifier.VALUE_KEY) &&
expectedValue instanceof String && bdHolder.matchesName((String) expectedValue)) {
// Fall back on bean name (or alias) match
continue;
}
if (actualValue == null && qualifier != null) {
// Fall back on default, but only if the qualifier is present
actualValue = AnnotationUtils.getDefaultValue(annotation, attributeName);
}
if (actualValue != null) {
actualValue = typeConverter.convertIfNecessary(actualValue, expectedValue.getClass());
}
if (!expectedValue.equals(actualValue)) {
return false;
}
}
return true;
}
@Nullable
protected Annotation getQualifiedElementAnnotation(RootBeanDefinition bd, Class<? extends Annotation> type) {
AnnotatedElement qualifiedElement = bd.getQualifiedElement();
return (qualifiedElement != null ? AnnotationUtils.getAnnotation(qualifiedElement, type) : null);
}
@Nullable
protected Annotation getFactoryMethodAnnotation(RootBeanDefinition bd, Class<? extends Annotation> type) {
Method resolvedFactoryMethod = bd.getResolvedFactoryMethod();
return (resolvedFactoryMethod != null ? AnnotationUtils.getAnnotation(resolvedFactoryMethod, type) : null);
}
/**
* Determine whether the given dependency declares an autowired annotation,
* checking its required flag.
* @see Autowired#required()
*/
@Override
public boolean isRequired(DependencyDescriptor descriptor) {
if (!super.isRequired(descriptor)) {
return false;
}
Autowired autowired = descriptor.getAnnotation(Autowired.class);
return (autowired == null || autowired.required());
}
/**
* Determine whether the given dependency declares a qualifier annotation.
* @see #isQualifier(Class)
* @see Qualifier
*/
@Override
public boolean hasQualifier(DependencyDescriptor descriptor) {
for (Annotation ann : descriptor.getAnnotations()) {
if (isQualifier(ann.annotationType())) {
return true;
}
}
return false;
}
/**
* Determine whether the given dependency declares a value annotation.
* @see Value
*/
@Override
@Nullable
public Object getSuggestedValue(DependencyDescriptor descriptor) {
Object value = findValue(descriptor.getAnnotations());
if (value == null) {
MethodParameter methodParam = descriptor.getMethodParameter();
if (methodParam != null) {
value = findValue(methodParam.getMethodAnnotations());
}
}
return value;
}
/**
* Determine a suggested value from any of the given candidate annotations.
*/
@Nullable
protected Object findValue(Annotation[] annotationsToSearch) {
if (annotationsToSearch.length > 0) { // qualifier annotations have to be local
AnnotationAttributes attr = AnnotatedElementUtils.getMergedAnnotationAttributes(
AnnotatedElementUtils.forAnnotations(annotationsToSearch), this.valueAnnotationType);
if (attr != null) {
return extractValue(attr);
}
}
return null;
}
/**
* Extract the value attribute from the given annotation.
* @since 4.3
*/
protected Object extractValue(AnnotationAttributes attr) {
Object value = attr.get(AnnotationUtils.VALUE);
if (value == null) {
throw new IllegalStateException("Value annotation must have a value attribute");
}
return value;
}
}
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