Spring Boot配置类处理
作者：互联网
ConfigurationClassPostProcessor处理所有配置类，包括@Component、@Bean、@Import注解等。由于配置类可能会引入新的配置类，新的配置类也需要被处理，所以ConfigurationClassPostProcessor采用do-while循环处理配置类，直到不存在未处理的配置类。
配置类的具体的处理工作交给ConfigurationClassParser，配置类引入新的配置类主要分两种情况：
1、配置类的Member Class是配置类、@ComponentScan扫描到配置类等情况，这些导入到rigistry的新配置类会递归的继续处理，并放到ConfigurationClassParser的configurationClasses属性中，这些都是已经处理过的
2、@Bean、@ImportResource、ImportBeanDefinitionRegistrar等不会直接注册到registry，而是由ConfigurationClassBeanDefinitionReader load到registry，这些配置类没有被处理过
配置类处理核心逻辑
这里的核心逻辑比较简单，如上所述，主要在ConfigurationClassPostProcessor#processConfigBeanDefinitions方法
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
String[] candidateNames = registry.getBeanDefinitionNames();
// 过滤出beanFactory中的配置类
for (String beanName : candidateNames) {
BeanDefinition beanDef = registry.getBeanDefinition(beanName);
if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
if (logger.isDebugEnabled()) {
logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
}
}
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
}
}
// Return immediately if no @Configuration classes were found
if (configCandidates.isEmpty()) {
return;
}
// 排序
configCandidates.sort((bd1, bd2) -> {
int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
return Integer.compare(i1, i2);
});
// Detect any custom bean name generation strategy supplied through the enclosing application context
SingletonBeanRegistry sbr = null;
if (registry instanceof SingletonBeanRegistry) {
sbr = (SingletonBeanRegistry) registry;
if (!this.localBeanNameGeneratorSet) {
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(
AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR);
if (generator != null) {
this.componentScanBeanNameGenerator = generator;
this.importBeanNameGenerator = generator;
}
}
}
if (this.environment == null) {
this.environment = new StandardEnvironment();
}
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
// candidates 待解析的配置类，alreadyParsed已经解析过的配置类
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
do {
StartupStep processConfig = this.applicationStartup.start("spring.context.config-classes.parse");
// 处理每个配置类，@Component、@Import、@ComponentScan、@Bean注解等都在这里处理
parser.parse(candidates);
parser.validate();
// parser.getConfigurationClasses()获取到的配置类都被处理过
Set<ConfigurationClass> 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());
}
// loadBeanDefinitions，@Bean、@ImportResource、ImportBeanDefinitionRegistrar注册bean
// 会在这里load到registry，这部分配置类未被处理，后面详细介绍
this.reader.loadBeanDefinitions(configClasses);
alreadyParsed.addAll(configClasses);
processConfig.tag("classCount", () -> String.valueOf(configClasses.size())).end();
candidates.clear();
// 说明导入了新的bean，可能存在未parse的配置类
if (registry.getBeanDefinitionCount() > candidateNames.length) {
String[] newCandidateNames = registry.getBeanDefinitionNames();
Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
Set<String> alreadyParsedClasses = new HashSet<>();
for (ConfigurationClass configurationClass : alreadyParsed) {
alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
}
// 将未parse的配置类放入candidates，下一轮do-while循环处理
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());
// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
}
if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
// Clear cache in externally provided MetadataReaderFactory; this is a no-op
// for a shared cache since it'll be cleared by the ApplicationContext.
((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
}
}
下面重点介绍do-while循环中两个重要步骤：parse和loadBeanDefinitions
parser.parse(candidates)
在外层的do-while循环中，将一组配置类解析的具体工作交给ConfigurationClassParser。该类的处理存在递归调用，比较复杂，调用链路简图如下
解析一组配置类
parse(Set)处理一组配置类，该方法在ConfigurationClassPostProcessor在do-while循环中调用。该方法在for循环中逐个解析所有配置类，最后调用一下deferredImportSelectorHandler，用来处理DeferredImportSelector。
public void parse(Set<BeanDefinitionHolder> configCandidates) {
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);
}
}
this.deferredImportSelectorHandler.process();
}
解析一个配置类
三个parse方法都调用了processConfigurationClass方法，parse如下，仅仅是将不同的入参统一成ConfigurationClass
protected final void parse(@Nullable String className, String beanName) throws IOException {
Assert.notNull(className, "No bean class name for configuration class bean definition");
MetadataReader reader = this.metadataReaderFactory.getMetadataReader(className);
processConfigurationClass(new ConfigurationClass(reader, beanName), DEFAULT_EXCLUSION_FILTER);
}
protected final void parse(Class<?> clazz, String beanName) throws IOException {
processConfigurationClass(new ConfigurationClass(clazz, beanName), DEFAULT_EXCLUSION_FILTER);
}
protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
processConfigurationClass(new ConfigurationClass(metadata, beanName), DEFAULT_EXCLUSION_FILTER);
}
processConfigurationClass方法处理了三件事情
1、如果当前configClass存在existingClass（配置类已经处理过），如果existingClass和configClass都是被其他配置类导入的，则合并被导入的类，不处理configClass；如果configClass不是被导入的，则重新处理这个类
2、do-while循环遍历一个配置类的所有父类，调用doProcessConfigurationClass处理配置类及每个父类
3、处理完配置类后加入Map configurationClasses
protected void processConfigurationClass(ConfigurationClass configClass, Predicate<String> filter) throws IOException {
if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
return;
}
ConfigurationClass existingClass = this.configurationClasses.get(configClass);
if (existingClass != null) {
if (configClass.isImported()) {
if (existingClass.isImported()) {
existingClass.mergeImportedBy(configClass);
}
// Otherwise ignore new imported config class; existing non-imported class overrides it.
return;
}
else {
// 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.knownSuperclasses.values().removeIf(configClass::equals);
}
}
// Recursively process the configuration class and its superclass hierarchy.
SourceClass sourceClass = asSourceClass(configClass, filter);
do {
sourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);
}
while (sourceClass != null);
this.configurationClasses.put(configClass, configClass);
}
配置类的具体解析
doProcessConfigurationClass具体处理每个配置类或其父类，配置类即configClass，当前要处理的类即sourceClass。doProcessConfigurationClass主要获取到sourceClass类、接口、方法、属性上的注解，并进行特定处理，下面分别介绍
1、处理MemberClasses
标注了@Component都会被处理，MemberClass就是内部类
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
processMemberClasses(configClass, sourceClass, filter);
}
processMemberClasses获取sourceClass的所有是配置类的MemberClass，调用processConfigurationClass当作配置类处理，candidate.asConfigClass(configClass)指定了内部类是被哪个配置类导入的。这里会存在递归调用
private void processMemberClasses(ConfigurationClass configClass, SourceClass sourceClass,
Predicate<String> filter) throws IOException {
Collection<SourceClass> memberClasses = sourceClass.getMemberClasses();
if (!memberClasses.isEmpty()) {
List<SourceClass> candidates = new ArrayList<>(memberClasses.size());
for (SourceClass memberClass : memberClasses) {
if (ConfigurationClassUtils.isConfigurationCandidate(memberClass.getMetadata()) &&
!memberClass.getMetadata().getClassName().equals(configClass.getMetadata().getClassName())) {
candidates.add(memberClass);
}
}
OrderComparator.sort(candidates);
for (SourceClass candidate : candidates) {
if (this.importStack.contains(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
}
else {
this.importStack.push(configClass);
try {
processConfigurationClass(candidate.asConfigClass(configClass), filter);
}
finally {
this.importStack.pop();
}
}
}
}
}
2、处理@PropertySource
PropertySource作用是导入配置文件
3、处理@ComponentScan
通过componentScanParser扫描bean，对扫到的配置类调用parse(String, String)重载方法进行解析，这里也存在递归调用
// Process any @ComponentScan annotations
Set<AnnotationAttributes> 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<BeanDefinitionHolder> 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());
}
}
}
}
4、处理@Import
处理@Import注解比较复杂，首先从sourceClass查找Import进来的类，然后分情况处理这些类。
查找Import类
通过尾递归查找所有导入的类
private Set<SourceClass> getImports(SourceClass sourceClass) throws IOException {
Set<SourceClass> imports = new LinkedHashSet<>();
Set<SourceClass> visited = new LinkedHashSet<>();
collectImports(sourceClass, imports, visited);
return imports;
}
递归方法collectImports。获取sourceClass上所有注解，如果注解不是@Import，继续搜索collectImports查找注解上的@Import；如果注解是@Import，获取Import进来的类，加入到imports
private void collectImports(SourceClass sourceClass, Set<SourceClass> imports, Set<SourceClass> visited)
throws IOException {
if (visited.add(sourceClass)) {
for (SourceClass annotation : sourceClass.getAnnotations()) {
String annName = annotation.getMetadata().getClassName();
if (!annName.equals(Import.class.getName())) {
collectImports(annotation, imports, visited);
}
}
imports.addAll(sourceClass.getAnnotationAttributes(Import.class.getName(), "value"));
}
}
Import类处理
for循环对所有Import进来的类，分四种情况处理
- 如果是DeferredImportSelector，调用deferredImportSelectorHandler#handle处理，细节后续介绍
- 如果是普通的ImportSelector，实例化该Selector并selectImport，调用processImports递归处理这些类
- 如果是ImportBeanDefinitionRegistrar，调用configClass#addImportBeanDefinitionRegistrar暂存该Registrar，后续通过ConfigurationClassBeanDefinitionReader再调用该registrat注册类
- 如果都不是以上情况，则当作一个配置类调用processConfigurationClass处理
private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
Collection<SourceClass> importCandidates, Predicate<String> exclusionFilter,
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) {
if (candidate.isAssignable(ImportSelector.class)) {
// Candidate class is an ImportSelector -> delegate to it to determine imports
Class<?> candidateClass = candidate.loadClass();
ImportSelector selector = ParserStrategyUtils.instantiateClass(candidateClass, ImportSelector.class,
this.environment, this.resourceLoader, this.registry);
Predicate<String> selectorFilter = selector.getExclusionFilter();
if (selectorFilter != null) {
exclusionFilter = exclusionFilter.or(selectorFilter);
}
if (selector instanceof DeferredImportSelector) {
this.deferredImportSelectorHandler.handle(configClass, (DeferredImportSelector) selector);
}
else {
String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames, exclusionFilter);
processImports(configClass, currentSourceClass, importSourceClasses, exclusionFilter, false);
}
}
else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
// Candidate class is an ImportBeanDefinitionRegistrar ->
// delegate to it to register additional bean definitions
Class<?> candidateClass = candidate.loadClass();
ImportBeanDefinitionRegistrar registrar =
ParserStrategyUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class,
this.environment, this.resourceLoader, this.registry);
configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
}
else {
// Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
// process it as an @Configuration class
this.importStack.registerImport(
currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
processConfigurationClass(candidate.asConfigClass(configClass), exclusionFilter);
}
}
}
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();
}
}
}
5、处理@ImportResource
resource里面可能定义了BeanDefinition，通过该注解导入resource。处理该注解仅将resource暂存在configClass里，后续再通过ConfigurationClassBeanDefinitionReader来注册BeanDefinition
AnnotationAttributes importResource =
AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
if (importResource != null) {
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);
}
}
6、处理@Bean
处理@Bean首先解析出beanMethod，然后暂存在configClass里，后续通过ConfigurationClassBeanDefinitionReader注册BeanDifinition
// Process individual @Bean methods
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
7、处理接口
递归处理所有接口及父接口的@Bean注解
private void processInterfaces(ConfigurationClass configClass, SourceClass sourceClass) throws IOException {
for (SourceClass ifc : sourceClass.getInterfaces()) {
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(ifc);
for (MethodMetadata methodMetadata : beanMethods) {
if (!methodMetadata.isAbstract()) {
// A default method or other concrete method on a Java 8+ interface...
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
}
processInterfaces(configClass, ifc);
}
}
deferredImportSelectorHandler
deferredImportSelectorHandler用来处理DeferredImportSelector，有两个重要方法：
1、processImports的时候，如果遇到DeferredImportSelector，调用deferredImportSelectorHandler#handle进行处理
2、parse配置类时候，处理完所有配置类，调用deferredImportSelectorHandler#process方法统一处理DeferredImportSelector
DefferedImportSelector与ImportSelector的区别
processorImports时遇到ImportSelector，会立即selectImport；而对于DefferedImportSelector，会先暂存起来，处理完其他的配置类再统一处理DefferedImportSelector。当使用@Conditional注解注册beanDefinition会很有用。
handle和process方法
handler和process方法目的是实现deffered语义，即延迟处理，延迟到当前parse过程的其他配置类都处理过之后，再处理DefferedImportSelector。
handle方法
processImports的过程中会调用handle方法，如果 deferredImportSelectors == null，意味着process， 正在进行（开始process之前会将deferredImportSelectors置为null，这个方法被调用即处理DeferredImportSelector的过程中又import了DeferredImportSelector），此时则直接处理，DeferredImportSelector；否则直接加入list deferredImportSelectors中，等待process处理
process方法
开始process之前，将deferredImportSelectors置为null。然后实例化DeferredImportSelectorGroupingHandler，对所有的DefferedImportSelector注册到handler里，然后调用DeferredImportSelectorGroupingHandler#processGroupImports。
private class DeferredImportSelectorHandler {
// 暂存的deferredImportSelector
@Nullable
private List<DeferredImportSelectorHolder> deferredImportSelectors = new ArrayList<>();
public void handle(ConfigurationClass configClass, DeferredImportSelector importSelector) {
DeferredImportSelectorHolder holder = new DeferredImportSelectorHolder(configClass, importSelector);
if (this.deferredImportSelectors == null) {
DeferredImportSelectorGroupingHandler handler = new DeferredImportSelectorGroupingHandler();
handler.register(holder);
handler.processGroupImports();
}
else {
this.deferredImportSelectors.add(holder);
}
}
public void process() {
List<DeferredImportSelectorHolder> deferredImports = this.deferredImportSelectors;
this.deferredImportSelectors = null;
try {
if (deferredImports != null) {
DeferredImportSelectorGroupingHandler handler = new DeferredImportSelectorGroupingHandler();
deferredImports.sort(DEFERRED_IMPORT_COMPARATOR);
deferredImports.forEach(handler::register);
handler.processGroupImports();
}
}
finally {
this.deferredImportSelectors = new ArrayList<>();
}
}
}
DeferredImportSelectorGroupingHandler
process过程中，将处理逻辑委托给DeferredImportSelectorGroupingHandler，先register、然后processGroupImports，目的是实现Group语义：即多个DefferedImportSelector为一组，这多个DefferedImportSelector import进来的类可以放在一起，通过特定逻辑决定哪些最终要import进来
先看下DeferredImportSelector接口定义
DeferredImportSelector
public interface DeferredImportSelector extends ImportSelector {
// 相同Class<? extends Group>为相同的组，为null是DefaultDeferredImportSelectorGroup
@Nullable
default Class<? extends Group> getImportGroup() {
return null;
}
interface Group {
// 一个group中包含多个DeferredImportSelector，会调用该方法逐个处理。处理时需要暂存
// 每个DeferredImportSelector import进来的类
void process(AnnotationMetadata metadata, DeferredImportSelector selector);
// 调用process处理所有DeferredImportSelector之后，会调用该方法获取最终要import的类，
// 这里面可以实现特定过滤逻辑或其他逻辑
Iterable<Entry> selectImports();
// 封装import的一个className。metadata是配置类的metadata，importClassName是将要import
// 的className
class Entry {
private final AnnotationMetadata metadata;
private final String importClassName;
public Entry(AnnotationMetadata metadata, String importClassName) {
this.metadata = metadata;
this.importClassName = importClassName;
}
}
}
Group语义是在DeferredImportSelectorGrouping类实现的，如下
DeferredImportSelectorGrouping
DeferredImportSelectorGrouping封装了Group实例以及多个DeferredImportSelector。getImports调用group#process逐个处理所有的DeferredImportSelector，然后调用group#selectImports获取import的所有类
private static class DeferredImportSelectorGrouping {
private final DeferredImportSelector.Group group;
private final List<DeferredImportSelectorHolder> deferredImports = new ArrayList<>();
DeferredImportSelectorGrouping(Group group) {
this.group = group;
}
public void add(DeferredImportSelectorHolder deferredImport) {
this.deferredImports.add(deferredImport);
}
public Iterable<Group.Entry> getImports() {
for (DeferredImportSelectorHolder deferredImport : this.deferredImports) {
this.group.process(deferredImport.getConfigurationClass().getMetadata(),
deferredImport.getImportSelector());
}
return this.group.selectImports();
}
}
默认的Group是DefaultDeferredImportSelectorGroup
process方法就是简单调用selector#selectImports方法，并暂存起来；selectImports方法即返回所有selector import进来的类
private static class DefaultDeferredImportSelectorGroup implements Group {
private final List<Entry> imports = new ArrayList<>();
@Override
public void process(AnnotationMetadata metadata, DeferredImportSelector selector) {
for (String importClassName : selector.selectImports(metadata)) {
this.imports.add(new Entry(metadata, importClassName));
}
}
@Override
public Iterable<Entry> selectImports() {
return this.imports;
}
}
另一个实现是AutoConfigurationGroup
process方法也是暂存了所有import的类；selectImports包含了特定的过滤逻辑
private static class AutoConfigurationGroup
implements DeferredImportSelector.Group, BeanClassLoaderAware, BeanFactoryAware, ResourceLoaderAware {
private final Map<String, AnnotationMetadata> entries = new LinkedHashMap<>();
private final List<AutoConfigurationEntry> autoConfigurationEntries = new ArrayList<>();
@Override
public void process(AnnotationMetadata annotationMetadata, DeferredImportSelector deferredImportSelector) {
Assert.state(deferredImportSelector instanceof AutoConfigurationImportSelector,
() -> String.format("Only %s implementations are supported, got %s",
AutoConfigurationImportSelector.class.getSimpleName(),
deferredImportSelector.getClass().getName()));
AutoConfigurationEntry autoConfigurationEntry = ((AutoConfigurationImportSelector) deferredImportSelector)
.getAutoConfigurationEntry(annotationMetadata);
this.autoConfigurationEntries.add(autoConfigurationEntry);
for (String importClassName : autoConfigurationEntry.getConfigurations()) {
this.entries.putIfAbsent(importClassName, annotationMetadata);
}
}
@Override
public Iterable<Entry> selectImports() {
if (this.autoConfigurationEntries.isEmpty()) {
return Collections.emptyList();
}
Set<String> allExclusions = this.autoConfigurationEntries.stream()
.map(AutoConfigurationEntry::getExclusions).flatMap(Collection::stream).collect(Collectors.toSet());
Set<String> processedConfigurations = this.autoConfigurationEntries.stream()
.map(AutoConfigurationEntry::getConfigurations).flatMap(Collection::stream)
.collect(Collectors.toCollection(LinkedHashSet::new));
processedConfigurations.removeAll(allExclusions);
return sortAutoConfigurations(processedConfigurations, getAutoConfigurationMetadata()).stream()
.map((importClassName) -> new Entry(this.entries.get(importClassName), importClassName))
.collect(Collectors.toList());
}
}
最后看下DeferredImportSelectorGroupingHandler的register方法和processGroupImports方法
DeferredImportSelectorGroupingHandler实现细节
groupings属性
handler会处理所有的DeferredImportSelector，这个map按分组保存了DeferredImportSelector
key：如果DeferredImportSelector的group不为null，则key是group的Class对象；如果group是null，则key是该DeferredImportSelectorHolder对象。key本身没有作用，仅仅是通过key对所有的DeferredImportSelector分个组，后续对groups.values()进行遍历
value：是DeferredImportSelectorGrouping对象
private class DeferredImportSelectorGroupingHandler {
private final Map<Object, DeferredImportSelectorGrouping> groupings = new LinkedHashMap<>();
private final Map<AnnotationMetadata, ConfigurationClass> configurationClasses = new HashMap<>();
// 将DeferredImportSelector进行分组，并创建DeferredImportSelectorGrouping
public void register(DeferredImportSelectorHolder deferredImport) {
Class<? extends Group> group = deferredImport.getImportSelector().getImportGroup();
DeferredImportSelectorGrouping grouping = this.groupings.computeIfAbsent(
(group != null ? group : deferredImport),
key -> new DeferredImportSelectorGrouping(createGroup(group)));
grouping.add(deferredImport);
this.configurationClasses.put(deferredImport.getConfigurationClass().getMetadata(),
deferredImport.getConfigurationClass());
}
public void processGroupImports() {
// 对分好组的DeferredImportSelector分组处理
for (DeferredImportSelectorGrouping grouping : this.groupings.values()) {
Predicate<String> exclusionFilter = grouping.getCandidateFilter();
// 调用了DeferredImportSelectorGrouping#getImports方法。如上，里面调用了
// group#process、group#selectImports，通过Group的特定化逻辑获取到了这一组
// DeferredImportSelector import的类。然后forEach对所有的类通过processImports
// 处理
grouping.getImports().forEach(entry -> {
ConfigurationClass configurationClass = this.configurationClasses.get(entry.getMetadata());
try {
processImports(configurationClass, asSourceClass(configurationClass, exclusionFilter),
Collections.singleton(asSourceClass(entry.getImportClassName(), exclusionFilter)),
exclusionFilter, false);
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to process import candidates for configuration class [" +
configurationClass.getMetadata().getClassName() + "]", ex);
}
});
}
}
// 实例化group，如果DeferredImportSelector指定了Group类，则用指定的类实例化，否则是默认的
// DefaultDeferredImportSelectorGroup
private Group createGroup(@Nullable Class<? extends Group> type) {
Class<? extends Group> effectiveType = (type != null ? type : DefaultDeferredImportSelectorGroup.class);
return ParserStrategyUtils.instantiateClass(effectiveType, Group.class,
ConfigurationClassParser.this.environment,
ConfigurationClassParser.this.resourceLoader,
ConfigurationClassParser.this.registry);
}
}
reader.loadBeanDefinitions(configClasses)
parse的过程中，有几个地方导入的类会暂存在configClass中，再由ConfigurationClassBeanDefinitionReader load进beanFactory
1、processImports过程中，遇到ImportBeanDefinitionRegistrar
else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
// Candidate class is an ImportBeanDefinitionRegistrar ->
// delegate to it to register additional bean definitions
Class<?> candidateClass = candidate.loadClass();
ImportBeanDefinitionRegistrar registrar =
ParserStrategyUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class,
this.environment, this.resourceLoader, this.registry);
configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
}
private void loadBeanDefinitionsFromRegistrars(Map<ImportBeanDefinitionRegistrar, AnnotationMetadata> registrars) {
registrars.forEach((registrar, metadata) ->
registrar.registerBeanDefinitions(metadata, this.registry, this.importBeanNameGenerator));
}
2、@ImportResource
AnnotationAttributes importResource =
AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
if (importResource != null) {
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);
}
}
如果@ImportResource注解指定了BeanDefinitionReader类名，则根据配置文件后缀使用GroovyBeanDefinitionReader、XmlBeanDefinitionReader，使用reader来load
private void loadBeanDefinitionsFromImportedResources(
Map<String, Class<? extends BeanDefinitionReader>> importedResources) {
Map<Class<?>, BeanDefinitionReader> readerInstanceCache = new HashMap<>();
importedResources.forEach((resource, readerClass) -> {
// Default reader selection necessary?
if (BeanDefinitionReader.class == readerClass) {
if (StringUtils.endsWithIgnoreCase(resource, ".groovy")) {
// When clearly asking for Groovy, that's what they'll get...
readerClass = GroovyBeanDefinitionReader.class;
}
else if (shouldIgnoreXml) {
throw new UnsupportedOperationException("XML support disabled");
}
else {
// Primarily ".xml" files but for any other extension as well
readerClass = XmlBeanDefinitionReader.class;
}
}
BeanDefinitionReader reader = readerInstanceCache.get(readerClass);
if (reader == null) {
try {
// Instantiate the specified BeanDefinitionReader
reader = readerClass.getConstructor(BeanDefinitionRegistry.class).newInstance(this.registry);
// Delegate the current ResourceLoader to it if possible
if (reader instanceof AbstractBeanDefinitionReader) {
AbstractBeanDefinitionReader abdr = ((AbstractBeanDefinitionReader) reader);
abdr.setResourceLoader(this.resourceLoader);
abdr.setEnvironment(this.environment);
}
readerInstanceCache.put(readerClass, reader);
}
catch (Throwable ex) {
throw new IllegalStateException(
"Could not instantiate BeanDefinitionReader class [" + readerClass.getName() + "]");
}
}
// TODO SPR-6310: qualify relative path locations as done in AbstractContextLoader.modifyLocations
reader.loadBeanDefinitions(resource);
});
}
3、@Bean
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
标签：configClass,DeferredImportSelector,处理,Spring,配置,Boot,new,class,sourceClass 来源： https://blog.csdn.net/qq_32868023/article/details/123142318