解析@Import和@Bean和@PropertySource和@ImportResource





org.springframework.context.annotation.ConfigurationClassParser#doProcessConfigurationClass调用
org.springframework.context.annotation.ConfigurationClassParser#processImports









@Import注解作用
@ComponentScan这个注解配置的扫描路径可能扫描不到某个类,比如说第三方jar包(@ComponentScan往往是扫描自己工程),就需要@Import了加载第三方jar包的路径了.

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
List configCandidates = new ArrayList();
String[] candidateNames = registry.getBeanDefinitionNames();

for (String beanName : candidateNames) {
BeanDefinition beanDef = registry.getBeanDefinition(beanName);

if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
if (logger.isDebugEnabled()) {
logger.debug(“Bean definition has already been processed as a configuration class: “ + beanDef);
}
}
//查看是否是配置类
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {

configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
}
}
//如果没有配置类就直接返回
if (configCandidates.isEmpty()) {
return;
}

//对这些配置类根据Order排序
Collections.sort(configCandidates, new Comparator() {
@Override
public int compare(BeanDefinitionHolder bd1, BeanDefinitionHolder bd2) {
int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
return (i1 < i2) ? -1 : (i1 > i2) ? 1 : 0;
}
});

SingletonBeanRegistry sbr = null;
if (registry instanceof SingletonBeanRegistry) {
sbr = (SingletonBeanRegistry) registry;
if (!this.localBeanNameGeneratorSet && sbr.containsSingleton(CONFIGURATION_BEAN_NAME_GENERATOR)) {
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
this.componentScanBeanNameGenerator = generator;
this.importBeanNameGenerator = generator;
}
}
//创建配置类的解析类
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);

Set candidates = new LinkedHashSet(configCandidates);
Set alreadyParsed = new HashSet(configCandidates.size());
do {
// ConfigurationClassParser的parse方法进行解析，重点哈
parser.parse(candidates);
parser.validate();

Set configClasses = new LinkedHashSet(parser.getConfigurationClasses());
configClasses.removeAll(alreadyParsed);

// Read the model and create bean definitions based on its content
if (this.reader == null) {
this.reader = new ConfigurationClassBeanDefinitionReader(
registry, this.sourceExtractor, this.resourceLoader, this.environment,
this.importBeanNameGenerator, parser.getImportRegistry());
}
this.reader.loadBeanDefinitions(configClasses);
alreadyParsed.addAll(configClasses);

candidates.clear();
if (registry.getBeanDefinitionCount() > candidateNames.length) {
String[] newCandidateNames = registry.getBeanDefinitionNames();
Set oldCandidateNames = new HashSet(Arrays.asList(candidateNames));
Set alreadyParsedClasses = new HashSet();
for (ConfigurationClass configurationClass : alreadyParsed) {
alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
}
for (String candidateName : newCandidateNames) {
if (!oldCandidateNames.contains(candidateName)) {
BeanDefinition bd = registry.getBeanDefinition(candidateName);
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
!alreadyParsedClasses.contains(bd.getBeanClassName())) {
candidates.add(new BeanDefinitionHolder(bd, candidateName));
}
}
}
candidateNames = newCandidateNames;
}
}
while (!candidates.isEmpty());

if (sbr != null) {
if (!sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
}
}

if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
}
}


现在该进入ConfigurationClassParser类了

public void parse(Set configCandidates) {
this.deferredImportSelectors = new LinkedList();

for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
try {
if (bd instanceof AnnotatedBeanDefinition) {
parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
}
else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
}
else {
parse(bd.getBeanClassName(), holder.getBeanName());
}
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
“Failed to parse configuration class [“ + bd.getBeanClassName() + “]”, ex);
}
}

processDeferredImportSelectors();
}
//下面三种方法用于处理不同的BeanDefinition 类型，但最终都是使用的processConfigurationClass方法
protected final void parse(String className, String beanName) throws IOException {
MetadataReader reader = this.metadataReaderFactory.getMetadataReader(className);
processConfigurationClass(new ConfigurationClass(reader, beanName));
}

protected final void parse(Class<?> clazz, String beanName) throws IOException {
processConfigurationClass(new ConfigurationClass(clazz, beanName));
}

protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
processConfigurationClass(new ConfigurationClass(metadata, beanName));
}



可以看到配置类可能会是三种形式的存在，这三种形式的Bean在操作上有着部分不一样，但是大部分又是一样，所以Spring用这种模式来处理。不得不感叹人家设计的真好
接着往下看

protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
return;
}

ConfigurationClass existingClass = this.configurationClasses.get(configClass);
//在这里处理Configuration重复import
//如果同一个配置类被处理两次，两次都属于被import的则合并导入类，返回。如果配置类不是被导入的，则移除旧使用新的配置类
if (existingClass != null) {
if (configClass.isImported()) {
if (existingClass.isImported()) {
existingClass.mergeImportedBy(configClass);
}
return;
}
else {
this.configurationClasses.remove(configClass);
for (Iterator it = this.knownSuperclasses.values().iterator(); it.hasNext();) {
if (configClass.equals(it.next())) {
it.remove();
}
}
}
}

SourceClass sourceClass = asSourceClass(configClass);
do {
//接着往下看吧
sourceClass = doProcessConfigurationClass(configClass, sourceClass);
}
while (sourceClass != null);

this.configurationClasses.put(configClass, configClass);
}



protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {

// 处理递归类
processMemberClasses(configClass, sourceClass);

// 处理@PropertySource注解
for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), PropertySources.class,
org.springframework.context.annotation.PropertySource.class)) {
if (this.environment instanceof ConfigurableEnvironment) {
processPropertySource(propertySource);
}
else {
logger.warn(“Ignoring @PropertySource annotation on [“ + sourceClass.getMetadata().getClassName() +
“]. Reason: Environment must implement ConfigurableEnvironment”);
}
}

// 处理 @ComponentScan 注解
Set componentScans = AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
if (!componentScans.isEmpty() &&
!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
for (AnnotationAttributes componentScan : componentScans) {
// The config class is annotated with @ComponentScan -> perform the scan immediately
Set scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
// Check the set of scanned definitions for any further config classes and parse recursively if needed
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
//处理Import注解，这个是咱们的菜
processImports(configClass, sourceClass, getImports(sourceClass), true);

// 处理@ImportResource 注解
if (sourceClass.getMetadata().isAnnotated(ImportResource.class.getName())) {
AnnotationAttributes importResource =
AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
String[] resources = importResource.getStringArray(“locations”);
Class<? extends BeanDefinitionReader> readerClass = importResource.getClass(“reader”);
for (String resource : resources) {
String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
configClass.addImportedResource(resolvedResource, readerClass);
}
}

//处理包含@Bean注解的方法
Set beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}

// 处理普通方法
processInterfaces(configClass, sourceClass);


if (sourceClass.getMetadata().hasSuperClass()) {
String superclass = sourceClass.getMetadata().getSuperClassName();
if (!superclass.startsWith(“java”) && !this.knownSuperclasses.containsKey(superclass)) {
this.knownSuperclasses.put(superclass, configClass);
// Superclass found, return its annotation metadata and recurse
return sourceClass.getSuperClass();
}
}

return null;
}



看到这里好像突然发现了新大陆呀，原来我们经常见的@Bean、@ImportResource 、@Import、@ComponentScan、@PropertySource都是在这里处理的呀
咱们的重点还是放在@Import上，对其他几个注解感兴趣的同学可以自行研究一下

private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
Collection importCandidates, boolean checkForCircularImports) {

if (importCandidates.isEmpty()) {
return;
}

if (checkForCircularImports && isChainedImportOnStack(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
}
else {
this.importStack.push(configClass);
try {
for (SourceClass candidate : importCandidates) {
//如果实现了ImportSelector接口
if (candidate.isAssignable(ImportSelector.class)) {
Class<?> candidateClass = candidate.loadClass();
ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
ParserStrategyUtils.invokeAwareMethods(
selector, this.environment, this.resourceLoader, this.registry);
if (this.deferredImportSelectors != null && selector instanceof DeferredImportSelector) {
this.deferredImportSelectors.add(
new DeferredImportSelectorHolder(configClass, (DeferredImportSelector) selector));
}
else {
String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
Collection importSourceClasses = asSourceClasses(importClassNames);
processImports(configClass, currentSourceClass, importSourceClasses, false);
}
}
//如果实现了ImportBeanDefinitionRegistrar接口
else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
Class<?> candidateClass = candidate.loadClass();
ImportBeanDefinitionRegistrar registrar =
BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
ParserStrategyUtils.invokeAwareMethods(
registrar, this.environment, this.resourceLoader, this.registry);
configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
}
else {
//将import当成Configuration来使用就是我们的第一种应用的方式
this.importStack.registerImport(
currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
processConfigurationClass(candidate.asConfigClass(configClass));
}
}
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
“Failed to process import candidates for configuration class [“ +
configClass.getMetadata().getClassName() + “]”, ex);
}
finally {
this.importStack.pop();
}
}
}




1．解析@ImportResource流程


org.springframework.context.annotation.ConfigurationClassParser#doProcessConfigurationClass方法内部将@ImportResource配置的路径加入到
org.springframework.context.annotation.ConfigurationClass#importedResources这个LinkedHashMap容器里面,

然后实例化过程中org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader#loadBeanDefinitionsForConfigurationClass调用
org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader#loadBeanDefinitionsFromImportedResources获取
importedResources容器里面的路径,然后在循环遍历importedResources容器,然后把XmlBeanDefinitionReader.class反射实例化出来.再然后调用
org.springframework.beans.factory.support.AbstractBeanDefinitionReader#loadBeanDefinitions(java.lang.String),再调用
org.springframework.beans.factory.support.AbstractBeanDefinitionReader#loadBeanDefinitions(java.lang.String, java.util.Set) 开始进行xml 的解析