spring boot配置类注册深入解析
前言
spring ApplicationContext的刷新总体来看有两个过程，第一个是注册BeanDefinition，提供整个IOC容器初始化的材料；第二个是根据BeanDefinition加载bean。从spring boot开始，推荐使用的是注解驱动编程，借助大量的自动化配置类注入BeanDefinition，之前Spring使用XML方式注入BeanDefinition的基本废弃，因此了解自动化配置类如何注入BeanDefinition，条件注解如何生效，重要性不言而喻。本文将针对自动化配置起重要作用的ConfigurationClassPostProcessor进行深入解析，通过本文可以解答如下问题：
- 自动化配置类生效的机制，条件注解的处理过程
- spring boot自动化配置类，有的条件类不存在，工程里打开是标红的，spring boot解析时为什么不报错，又是如何通过编译的？
- @EnableXXXX到底是什么原理？注册BeanDefinition有哪些高端的姿势？
- @Configuration和@Component到底有什么区别。
本文源码见：源码
一张图总结整个配置类注册过程：
1. ConfigurationClassPostProcessor
ConfigurationClassPostProcessor，实现PriorityOrdered，主要有两个作用：
- 在postProcessBeanDefinitionRegistry注入beanDefinition。
- 在postProcessBeanFactory，替换@Configuration class注解的beanClass为cglib增强。同时注入一个BeanPostProcessor：ImportAwareBeanPostProcessor
核心逻辑如下：
- 先从当前BeanFactory找到所有含有@Configuration或者标有@Component/@ComponentScan/@Import/@ImportResource注解，或者有@Bean方法，作为初始化的配置类
- ConfigurationPhase.PARSE_CONFIGURATION阶段：使用ConfigurationClassParser，解析成所有的ConfigurationClass，包括其上的@import，以及@Bean method，全部解析并存到ConfigurationClass中。这个阶段一般不会load class。
- ConfigurationPhase.REGISTER_BEAN阶段：再把ConfigurationClass中的BeanMethod啥的注册到BeanDefinitionRegistry中，如@Import(ImportRegistrar)，则直接register。这个阶段可能会load class，同时对于@Bean方法上的注解，会继续处理。
- 获取到新注册的未处理的bean definition，继续循环处理下一批新增的配置类。
// ConfigurationClassPostProcessor
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
int registryId = System.identityHashCode(registry);
if (this.registriesPostProcessed.contains(registryId)) {
throw new IllegalStateException(
"postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
}
if (this.factoriesPostProcessed.contains(registryId)) {
throw new IllegalStateException(
"postProcessBeanFactory already called on this post-processor against " + registry);
}
this.registriesPostProcessed.add(registryId);
processConfigBeanDefinitions(registry);
}
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
List configCandidates = new ArrayList<>();
String[] candidateNames = registry.getBeanDefinitionNames();
// 先从当前factory找到所有含有@Configuration或者该bean标有@Component/@ComponentScan/@Import/@ImportResource注解，或者有@Bean方法。
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;
}
// Sort by previously determined @Order value, if applicable
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();
}
// Parse each @Configuration class
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 {
StartupStep processConfig = this.applicationStartup.start("spring.context.config-classes.parse");
// 1、使用ConfigurationClassParser，解析成所有的ConfigurationClass，包括其上的@import，以及@Bean method，全部解析并存到ConfigurationClass中
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());
}
// 2、再把ConfigurationClass中的BeanMethod啥的注册到BeanDefinitionRegistry中，如@Import(ImportRegistrar)，则直接register
this.reader.loadBeanDefinitions(configClasses);
alreadyParsed.addAll(configClasses);
processConfig.tag("classCount", () -> String.valueOf(configClasses.size())).end();
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())) {
// 3、获取到新注册的bean definition，继续循环处理
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();
}
}
首先介绍下，一个配置类什么时候是full模式，什么时候是lite模式：
- full模式：配置类标记有@Configuration且proxyBeanMethos=true/null，则是大模式
- lite模式，有两种情况：
- 配置类标记有@Configuration且proxyBeanMethos=false
- 配置类标记有@Component/@ComponentScan/@Import/@ImportResource注解，或者有@Bean方法，则是小的配置类。
只有上面两个模式的配置类，才会进一步处理，才会调用processConfigurationClass，包括内部类、ComponentScan扫描到的类、这一批新增加的类
// ConfigurationClassUtils
private static final Set candidateIndicators = new HashSet<>(8);
static {
candidateIndicators.add(Component.class.getName());
candidateIndicators.add(ComponentScan.class.getName());
candidateIndicators.add(Import.class.getName());
candidateIndicators.add(ImportResource.class.getName());
}
public static boolean checkConfigurationClassCandidate(
BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {
String className = beanDef.getBeanClassName();
if (className == null || beanDef.getFactoryMethodName() != null) {
return false;
}
AnnotationMetadata metadata;
if (beanDef instanceof AnnotatedBeanDefinition &&
className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) {
// Can reuse the pre-parsed metadata from the given BeanDefinition...
metadata = ((AnnotatedBeanDefinition) beanDef).getMetadata();
}
else if (beanDef instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) beanDef).hasBeanClass()) {
// Check already loaded Class if present...
// since we possibly can't even load the class file for this Class.
Class beanClass = ((AbstractBeanDefinition) beanDef).getBeanClass();
if (BeanFactoryPostProcessor.class.isAssignableFrom(beanClass) ||
BeanPostProcessor.class.isAssignableFrom(beanClass) ||
AopInfrastructureBean.class.isAssignableFrom(beanClass) ||
EventListenerFactory.class.isAssignableFrom(beanClass)) {
return false;
}
metadata = AnnotationMetadata.introspect(beanClass);
}
else {
try {
MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(className);
metadata = metadataReader.getAnnotationMetadata();
}
catch (IOException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Could not find class file for introspecting configuration annotations: " +
className, ex);
}
return false;
}
}
// 标记有@Configuration且proxyBeanMethos=true/null，则是大模式
Map config = metadata.getAnnotationAttributes(Configuration.class.getName());
if (config != null && !Boolean.FALSE.equals(config.get("proxyBeanMethods"))) {
beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
}
else if (config != null || isConfigurationCandidate(metadata)) {
// 标记有@Configuration且proxyBeanMethos=false，则是lite模式
// 该类标有@Component/@ComponentScan/@Import/@ImportResource注解，或者有@Bean方法，则是小的配置类。
beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
}
else {
return false;
}
// It's a full or lite configuration candidate... Let's determine the order value, if any.
Integer order = getOrder(metadata);
if (order != null) {
beanDef.setAttribute(ORDER_ATTRIBUTE, order);
}
return true;
}
public static boolean isConfigurationCandidate(AnnotationMetadata metadata) {
// Do not consider an interface or an annotation...
if (metadata.isInterface()) {
return false;
}
// Any of the typical annotations found?
for (String indicator : candidateIndicators) {
if (metadata.isAnnotated(indicator)) {
return true;
}
}
// Finally, let's look for @Bean methods...
return hasBeanMethods(metadata);
}
2. ConfigurationClassParser.parse
启动配置类只有DemoApplication，由于启动类已经加载为class了，这里AnnotationMetadata为StandardAnnotationMetadata，底层基于反射获取到注解等类信息；如果未加载class，则一般使用ASM读取类文件，避免过早加载类，实例为SimpleAnnotationMetadata，底层使用SimpleMetadataReader读取。
每一批类处理完成后，才调用deferredImportSelectorHandler.process方法，保证@Import defferred Import类最后处理。
public void parse(Set 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();
}
// StandardAnnotationMetadata
protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
processConfigurationClass(new ConfigurationClass(metadata, beanName), DEFAULT_EXCLUSION_FILTER);
}
protected final void parse(@Nullable String className, String beanName) throws IOException {
Assert.notNull(className, "No bean class name for configuration class bean definition");
// 利用metadataRederFactory读取，就是之前的ConcurrentReferenceCachingMetadataReaderFactory，最终得到的reader是SimpleMetadataReader
MetadataReader reader = this.metadataReaderFactory.getMetadataReader(className);
processConfigurationClass(new ConfigurationClass(reader, beanName), DEFAULT_EXCLUSION_FILTER);
}
ConfigurationClass(MetadataReader metadataReader, String beanName) {
Assert.notNull(beanName, "Bean name must not be null");
// 读取metadata
this.metadata = metadataReader.getAnnotationMetadata();
this.resource = metadataReader.getResource();
this.beanName = beanName;
}
最后，每个配置类，都会进入到processConfigurationClass这个方法进行处理，首先是看该配置类是否满足条件，不满足则不处理，否则递归处理，从当前类往上找到所有父类，不断处理。
在这过程中配置类是相同的，也就是说配置类ConfigurationClass会一直传递，用于存储获取的BeanMethod/import类等，但是sourceClass会变化，依次为当前类，父类，父父类…
protected void processConfigurationClass(ConfigurationClass configClass, Predicate 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);
}
/**
* Apply processing and build a complete {@link ConfigurationClass} by reading the
* annotations, members and methods from the source class. This method can be called
* multiple times as relevant sources are discovered.
* @param configClass the configuration class being build
* @param sourceClass a source class
* @return the superclass, or {@code null} if none found or previously processed
*/
@Nullable
protected final SourceClass doProcessConfigurationClass(
ConfigurationClass configClass, SourceClass sourceClass, Predicate filter)
throws IOException {
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
// 1、在扫描一个java config类之前，第一步先处理内部类并注册，注意内部类必须标记有@Component或者有@Bean method，然后再处理@Bean方法
// Recursively process any member (nested) classes first
processMemberClasses(configClass, sourceClass, filter);
}
// Process any @PropertySource annotations
for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), PropertySources.class,
org.springframework.context.annotation.PropertySource.class)) {
if (this.environment instanceof ConfigurableEnvironment) {
processPropertySource(propertySource);
}
else {
logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
"]. Reason: Environment must implement ConfigurableEnvironment");
}
}
// Process any @ComponentScan annotations
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());
}
}
}
}
// Process any @Import annotations
processImports(configClass, sourceClass, getImports(sourceClass), filter, true);
// Process any @ImportResource annotations
AnnotationAttributes importResource =
AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
if (importResource != null) {
String[] resources = importResource.getStringArray("locations");
Class readerClass = importResource.getClass("reader");
for (String resource : resources) {
String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
configClass.addImportedResource(resolvedResource, readerClass);
}
}
// Process individual @Bean methods
Set beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
// Process default methods on interfaces
processInterfaces(configClass, sourceClass);
// Process superclass, if any
if (sourceClass.getMetadata().hasSuperClass()) {
String superclass = sourceClass.getMetadata().getSuperClassName();
if (superclass != null && !superclass.startsWith("java") &&
!this.knownSuperclasses.containsKey(superclass)) {
this.knownSuperclasses.put(superclass, configClass);
// Superclass found, return its annotation metadata and recurse
return sourceClass.getSuperClass();
}
}
// No superclass -> processing is complete
return null;
}
3. 处理sourceClass的内部类
如果配置类标记有@Component，对于每个sourceClass，则会处理sourceClass符合条件的内部类，也就是符合isConfigurationCandidate，标有@Configuration/@Component/@ComponentScan/@Import/@ImportResource注解，或者有@Bean方法，才会进行处理。可以看到调用的依旧是processConfigurationClass，构成递归，底层对每个内部类，依旧会进行条件判断。
private void processMemberClasses(ConfigurationClass configClass, SourceClass sourceClass,
Predicate filter) throws IOException {
Collection memberClasses = sourceClass.getMemberClasses();
if (!memberClasses.isEmpty()) {
List 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();
}
}
}
}
}
4. 处理sourceClass上的注解PropertySource
之后处理sourceClass上的注解PropertySource，并添加到environment
private void processPropertySource(AnnotationAttributes propertySource) throws IOException {
String name = propertySource.getString("name");
String[] locations = propertySource.getStringArray("value");
boolean ignoreResourceNotFound = propertySource.getBoolean("ignoreResourceNotFound");
Assert.isTrue(locations.length > 0, "At least one @PropertySource(value) location is required");
for (String location : locations) {
try {
String resolvedLocation = this.environment.resolveRequiredPlaceholders(location);
Resource resource = this.resourceLoader.getResource(resolvedLocation);
ResourcePropertySource rps = (StringUtils.hasText(name) ?
new ResourcePropertySource(name, resource) : new ResourcePropertySource(resource));
addPropertySource(rps);
}
catch (IllegalArgumentException ex) {
// from resolveRequiredPlaceholders
if (!ignoreResourceNotFound) {
throw ex;
}
}
catch (FileNotFoundException ex) {
// from ResourcePropertySource constructor
if (!ignoreResourceNotFound) {
throw ex;
}
}
}
}
5. 处理sourceClass的注解ComponentScan
之后处理sourceClass的注解ComponentScan，默认不指定包的话，是ComponentScan注解声明类所在的包。而且扫描通过的话，会直接注册该类对应的bean definition到BeanDefinitionRegistry中，其上的条件注解也会生效，也可以使用includeFilter/excludeFilter来进一步过滤。底层使用的是ClassPathBeanDefinitionScanner#doScan方法。如果使用findCandidateComponents，则不会有注册功能，仅仅是扫描而已。如果扫描到的类标有@Configuration/@Component/@ComponentScan/@Import/@ImportResource注解，或者有@Bean方法，会继续进行processConfigurationClass处理。最终注册为ScannedGenericBeanDefinition。
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());
}
}
}
}
在本实例中，DemoApplication上标记有@ComponentScan，所以会进行扫描。
且由于没有配置扫描的包路径，默认为声明类所在的包：
protected Set doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set beanDefinitions = new LinkedHashSet<>();
for (String basePackage : basePackages) {
// 从类路径找到符合条件的bean definition
Set candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
// 注册符合条件的bean definition到registry
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}
protected boolean checkCandidate(String beanName, BeanDefinition beanDefinition) throws IllegalStateException {
if (!this.registry.containsBeanDefinition(beanName)) {
return true;
}
BeanDefinition existingDef = this.registry.getBeanDefinition(beanName);
BeanDefinition originatingDef = existingDef.getOriginatingBeanDefinition();
if (originatingDef != null) {
existingDef = originatingDef;
}
// 如果扫描到的bean已经注册了，beanName一致，则可能会报错
if (isCompatible(beanDefinition, existingDef)) {
return false;
}
throw new ConflictingBeanDefinitionException("Annotation-specified bean name '" + beanName +
"' for bean class [" + beanDefinition.getBeanClassName() + "] conflicts with existing, " +
"non-compatible bean definition of same name and class [" + existingDef.getBeanClassName() + "]");
}
public Set findCandidateComponents(String basePackage) {
if (this.componentsIndex != null && indexSupportsIncludeFilters()) {
return addCandidateComponentsFromIndex(this.componentsIndex, basePackage);
}
else {
return scanCandidateComponents(basePackage);
}
}
private Set scanCandidateComponents(String basePackage) {
Set candidates = new LinkedHashSet<>();
try {
// 类文件全部解析为resource
String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
resolveBasePackage(basePackage) + '/' + this.resourcePattern;
Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath);
boolean traceEnabled = logger.isTraceEnabled();
boolean debugEnabled = logger.isDebugEnabled();
for (Resource resource : resources) {
if (traceEnabled) {
logger.trace("Scanning " + resource);
}
try {
// 使用ASM读取，解析类文件上的注解
MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
if (isCandidateComponent(metadataReader)) {
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
sbd.setSource(resource);
// 符合条件的resource，会构建为ScannedGenericBeanDefinition
if (isCandidateComponent(sbd)) {
if (debugEnabled) {
logger.debug("Identified candidate component class: " + resource);
}
candidates.add(sbd);
}
else {
if (debugEnabled) {
logger.debug("Ignored because not a concrete top-level class: " + resource);
}
}
}
else {
if (traceEnabled) {
logger.trace("Ignored because not matching any filter: " + resource);
}
}
}
catch (FileNotFoundException ex) {
if (traceEnabled) {
logger.trace("Ignored non-readable " + resource + ": " + ex.getMessage());
}
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to read candidate component class: " + resource, ex);
}
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
}
return candidates;
}
protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
for (TypeFilter tf : this.excludeFilters) {
if (tf.match(metadataReader, getMetadataReaderFactory())) {
return false;
}
}
for (TypeFilter tf : this.includeFilters) {
if (tf.match(metadataReader, getMetadataReaderFactory())) {
// 是否符合环境变量等条件，@Conditional
return isConditionMatch(metadataReader);
}
}
return false;
}
最后，扫描得到两个candiate bean definition：HelloController和UserService
6. 处理sourceClass的注解Import
之后处理sourceClass的注解@Import，收集注解上的class，得到importCandidates。import的class有三种：
- DeferredImportSelector，实例化后交给deferredImportSelectorHandler.handle处理，主要是分组进行聚合，然后排序，保证添加到beanDefinitionRegistry时是有序的，尤其是在@ConditionalOnMissingBean时，要覆盖，很有用。
- ImportSelector，实例化selectImport后，继续调用processImports，一般最后添加的也是普通配置类
- ImportBeanDefinitionRegistrar，实例话后，添加到configClass中，待会进行registerBean。
- 普通配置类，继续调用processConfigurationClass处理。
private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
Collection importCandidates, Predicate 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 selectorFilter = selector.getExclusionFilter();
if (selectorFilter != null) {
exclusionFilter = exclusionFilter.or(selectorFilter);
}
if (selector instanceof DeferredImportSelector) {
// 交给deferredImportSelectorHandler处理
this.deferredImportSelectorHandler.handle(configClass, (DeferredImportSelector) selector);
}
else {
// 找到slelector方法里所有导入的类，继续调用processImports
String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
Collection 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());
// 普通配置类
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();
}
}
}
6.1 自动化配置类过滤和排序
自动化配置类的导入，是通过EnableAutoConfiguration注解导入的，默认会有两个：
- org.springframework.boot.autoconfigure.AutoConfigurationPackages.Registrar，主要是注册当前EnableAutoConfiguration的basePackage，对应的bean为BasePackages，beanName为AutoConfigurationPackages.class.getName()
- 自动化配置使用的是AutoConfigurationImportSelector，实现了DeferredImportSelector，这里只是暂存到handler中，等这一批处理完，DeferredImportSelector list才会进行统一处理注入。
private class DeferredImportSelectorHandler {
@Nullable
private List deferredImportSelectors = new ArrayList<>();
/**
* Handle the specified {@link DeferredImportSelector}. If deferred import
* selectors are being collected, this registers this instance to the list. If
* they are being processed, the {@link DeferredImportSelector} is also processed
* immediately according to its {@link DeferredImportSelector.Group}.
* @param configClass the source configuration class
* @param importSelector the selector to handle
*/
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 {
// 添加到list，暂存起来
this.deferredImportSelectors.add(holder);
}
}
public void process() {
List deferredImports = this.deferredImportSelectors;
this.deferredImportSelectors = null;
try {
if (deferredImports != null) {
DeferredImportSelectorGroupingHandler handler = new DeferredImportSelectorGroupingHandler();
// 对所有deferred import selector排序，分类注册，最后分组处理
deferredImports.sort(DEFERRED_IMPORT_COMPARATOR);
deferredImports.forEach(handler::register);
handler.processGroupImports();
}
}
finally {
this.deferredImportSelectors = new ArrayList<>();
}
}
}
处理defer selector import，逐个注入到group handler中，最后再统一selectimport
private class DeferredImportSelectorGroupingHandler {
private final Map groupings = new LinkedHashMap<>();
private final Map configurationClasses = new HashMap<>();
public void register(DeferredImportSelectorHolder deferredImport) {
// 对于自动导入类，默认是AutoConfigurationGroup class，相同group class会放到一起
Class 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() {
for (DeferredImportSelectorGrouping grouping : this.groupings.values()) {
Predicate exclusionFilter = grouping.getCandidateFilter();
// 对于每个分组，逐个selectImport，最后调用processImports()
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);
}
});
}
}
private Group createGroup(@Nullable Class type) {
Class effectiveType = (type != null ? type : DefaultDeferredImportSelectorGroup.class);
return ParserStrategyUtils.instantiateClass(effectiveType, Group.class,
ConfigurationClassParser.this.environment,
ConfigurationClassParser.this.resourceLoader,
ConfigurationClassParser.this.registry);
}
}
private static class DeferredImportSelectorGrouping {
private final DeferredImportSelector.Group group;
private final List deferredImports = new ArrayList<>();
DeferredImportSelectorGrouping(Group group) {
this.group = group;
}
public void add(DeferredImportSelectorHolder deferredImport) {
this.deferredImports.add(deferredImport);
}
/**
* Return the imports defined by the group.
* @return each import with its associated configuration class
*/
public Iterable getImports() {
for (DeferredImportSelectorHolder deferredImport : this.deferredImports) {
// 对于每个group实现类及其添加的defer import selector，对自动配置类则是AutoConfigurationGroup，先用group处理下，最后再select imports
this.group.process(deferredImport.getConfigurationClass().getMetadata(),
deferredImport.getImportSelector());
}
// 最后再select imports
return this.group.selectImports();
}
public Predicate getCandidateFilter() {
Predicate mergedFilter = DEFAULT_EXCLUSION_FILTER;
for (DeferredImportSelectorHolder deferredImport : this.deferredImports) {
Predicate selectorFilter = deferredImport.getImportSelector().getExclusionFilter();
if (selectorFilter != null) {
mergedFilter = mergedFilter.or(selectorFilter);
}
}
return mergedFilter;
}
}
group.process主要是调用AutoConfigurationImportSelector获取到所有的自动化配置类，并暂存到autoConfigurationEntries中。在获取自动化配置类的过程中，会使用META-INF/spring.factories中的AutoConfigurationImportFilter对自动化配置类进行提前过滤，目前主要有三个：
org.springframework.boot.autoconfigure.AutoConfigurationImportFilter=
org.springframework.boot.autoconfigure.condition.OnBeanCondition,
org.springframework.boot.autoconfigure.condition.OnClassCondition,
org.springframework.boot.autoconfigure.condition.OnWebApplicationCondition
private static class AutoConfigurationGroup
implements DeferredImportSelector.Group, BeanClassLoaderAware, BeanFactoryAware, ResourceLoaderAware {
private final Map entries = new LinkedHashMap<>();
private final List autoConfigurationEntries = new ArrayList<>();
private ClassLoader beanClassLoader;
private BeanFactory beanFactory;
private ResourceLoader resourceLoader;
private AutoConfigurationMetadata autoConfigurationMetadata;
@Override
public void setBeanClassLoader(ClassLoader classLoader) {
this.beanClassLoader = classLoader;
}
@Override
public void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
@Override
public void setResourceLoader(ResourceLoader resourceLoader) {
this.resourceLoader = resourceLoader;
}
@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 selectImports() {
if (this.autoConfigurationEntries.isEmpty()) {
return Collections.emptyList();
}
Set allExclusions = this.autoConfigurationEntries.stream()
.map(AutoConfigurationEntry::getExclusions).flatMap(Collection::stream).collect(Collectors.toSet());
Set 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());
}
private AutoConfigurationMetadata getAutoConfigurationMetadata() {
if (this.autoConfigurationMetadata == null) {
this.autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);
}
return this.autoConfigurationMetadata;
}
private List sortAutoConfigurations(Set configurations,
AutoConfigurationMetadata autoConfigurationMetadata) {
return new AutoConfigurationSorter(getMetadataReaderFactory(), autoConfigurationMetadata)
.getInPriorityOrder(configurations);
}
private MetadataReaderFactory getMetadataReaderFactory() {
try {
return this.beanFactory.getBean(SharedMetadataReaderFactoryContextInitializer.BEAN_NAME,
MetadataReaderFactory.class);
}
catch (NoSuchBeanDefinitionException ex) {
return new CachingMetadataReaderFactory(this.resourceLoader);
}
}
}
提前过滤主要是利用META-INF/spring-autoconfigure-metadata.properties中的配置元数据，只能对class不存在时，导致的条件不生效进行过滤，例如对于conditionalOnBean可以提前过滤掉一部分。
abstract class FilteringSpringBootCondition extends SpringBootCondition
implements AutoConfigurationImportFilter, BeanFactoryAware, BeanClassLoaderAware {
private BeanFactory beanFactory;
private ClassLoader beanClassLoader;
// 实现AutoConfigurationImportFilter，提前过滤掉部分不生效的自动化配置类。
@Override
public boolean[] match(String[] autoConfigurationClasses, AutoConfigurationMetadata autoConfigurationMetadata) {
ConditionEvaluationReport report = ConditionEvaluationReport.find(this.beanFactory);
ConditionOutcome[] outcomes = getOutcomes(autoConfigurationClasses, autoConfigurationMetadata);
boolean[] match = new boolean[outcomes.length];
for (int i = 0; i < outcomes.length; i++) {
match[i] = (outcomes[i] == null || outcomes[i].isMatch());
if (!match[i] && outcomes[i] != null) {
logOutcome(autoConfigurationClasses[i], outcomes[i]);
if (report != null) {
report.recordConditionEvaluation(autoConfigurationClasses[i], this, outcomes[i]);
}
}
}
return match;
}
protected abstract ConditionOutcome[] getOutcomes(String[] autoConfigurationClasses,
AutoConfigurationMetadata autoConfigurationMetadata);
过滤掉后，只能77个，原先有200多个。
0 = "org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration"
1 = "org.springframework.boot.autoconfigure.aop.AopAutoConfiguration"
2 = "org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration"
3 = "org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration"
4 = "org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration"
5 = "org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration"
6 = "org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration"
7 = "org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration"
8 = "org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration"
9 = "org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration"
10 = "org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration"
11 = "org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration"
12 = "org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration"
13 = "org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration"
14 = "org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration"
15 = "org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration"
16 = "org.springframework.boot.autoconfigure.availability.ApplicationAvailabilityAutoConfiguration"
17 = "org.springframework.boot.autoconfigure.sql.init.SqlInitializationAutoConfiguration"
18 = "org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration"
19 = "org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration"
20 = "org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration"
21 = "org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration"
22 = "org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration"
23 = "org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration"
24 = "org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration"
25 = "org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration"
26 = "org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration"
27 = "org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration"
28 = "org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration"
29 = "org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration"
30 = "org.springframework.boot.actuate.autoconfigure.audit.AuditAutoConfiguration"
31 = "org.springframework.boot.actuate.autoconfigure.audit.AuditEventsEndpointAutoConfiguration"
32 = "org.springframework.boot.actuate.autoconfigure.availability.AvailabilityHealthContributorAutoConfiguration"
33 = "org.springframework.boot.actuate.autoconfigure.availability.AvailabilityProbesAutoConfiguration"
34 = "org.springframework.boot.actuate.autoconfigure.beans.BeansEndpointAutoConfiguration"
35 = "org.springframework.boot.actuate.autoconfigure.cache.CachesEndpointAutoConfiguration"
36 = "org.springframework.boot.actuate.autoconfigure.cloudfoundry.servlet.CloudFoundryActuatorAutoConfiguration"
37 = "org.springframework.boot.actuate.autoconfigure.condition.ConditionsReportEndpointAutoConfiguration"
38 = "org.springframework.boot.actuate.autoconfigure.context.properties.ConfigurationPropertiesReportEndpointAutoConfiguration"
39 = "org.springframework.boot.actuate.autoconfigure.context.ShutdownEndpointAutoConfiguration"
40 = "org.springframework.boot.actuate.autoconfigure.endpoint.EndpointAutoConfiguration"
41 = "org.springframework.boot.actuate.autoconfigure.endpoint.jmx.JmxEndpointAutoConfiguration"
42 = "org.springframework.boot.actuate.autoconfigure.endpoint.web.WebEndpointAutoConfiguration"
43 = "org.springframework.boot.actuate.autoconfigure.env.EnvironmentEndpointAutoConfiguration"
44 = "org.springframework.boot.actuate.autoconfigure.health.HealthContributorAutoConfiguration"
45 = "org.springframework.boot.actuate.autoconfigure.health.HealthEndpointAutoConfiguration"
46 = "org.springframework.boot.actuate.autoconfigure.info.InfoContributorAutoConfiguration"
47 = "org.springframework.boot.actuate.autoconfigure.info.InfoEndpointAutoConfiguration"
48 = "org.springframework.boot.actuate.autoconfigure.jdbc.DataSourceHealthContributorAutoConfiguration"
49 = "org.springframework.boot.actuate.autoconfigure.logging.LogFileWebEndpointAutoConfiguration"
50 = "org.springframework.boot.actuate.autoconfigure.logging.LoggersEndpointAutoConfiguration"
51 = "org.springframework.boot.actuate.autoconfigure.management.HeapDumpWebEndpointAutoConfiguration"
52 = "org.springframework.boot.actuate.autoconfigure.management.ThreadDumpEndpointAutoConfiguration"
53 = "org.springframework.boot.actuate.autoconfigure.metrics.CompositeMeterRegistryAutoConfiguration"
54 = "org.springframework.boot.actuate.autoconfigure.metrics.JvmMetricsAutoConfiguration"
55 = "org.springframework.boot.actuate.autoconfigure.metrics.LogbackMetricsAutoConfiguration"
56 = "org.springframework.boot.actuate.autoconfigure.metrics.MetricsAutoConfiguration"
57 = "org.springframework.boot.actuate.autoconfigure.metrics.MetricsEndpointAutoConfiguration"
58 = "org.springframework.boot.actuate.autoconfigure.metrics.SystemMetricsAutoConfiguration"
59 = "org.springframework.boot.actuate.autoconfigure.metrics.cache.CacheMetricsAutoConfiguration"
60 = "org.springframework.boot.actuate.autoconfigure.metrics.export.simple.SimpleMetricsExportAutoConfiguration"
61 = "org.springframework.boot.actuate.autoconfigure.metrics.integration.IntegrationMetricsAutoConfiguration"
62 = "org.springframework.boot.actuate.autoconfigure.metrics.jdbc.DataSourcePoolMetricsAutoConfiguration"
63 = "org.springframework.boot.actuate.autoconfigure.metrics.startup.StartupTimeMetricsListenerAutoConfiguration"
64 = "org.springframework.boot.actuate.autoconfigure.metrics.task.TaskExecutorMetricsAutoConfiguration"
65 = "org.springframework.boot.actuate.autoconfigure.metrics.web.client.HttpClientMetricsAutoConfiguration"
66 = "org.springframework.boot.actuate.autoconfigure.metrics.web.servlet.WebMvcMetricsAutoConfiguration"
67 = "org.springframework.boot.actuate.autoconfigure.metrics.web.tomcat.TomcatMetricsAutoConfiguration"
68 = "org.springframework.boot.actuate.autoconfigure.scheduling.ScheduledTasksEndpointAutoConfiguration"
69 = "org.springframework.boot.actuate.autoconfigure.security.servlet.ManagementWebSecurityAutoConfiguration"
70 = "org.springframework.boot.actuate.autoconfigure.startup.StartupEndpointAutoConfiguration"
71 = "org.springframework.boot.actuate.autoconfigure.system.DiskSpaceHealthContributorAutoConfiguration"
72 = "org.springframework.boot.actuate.autoconfigure.trace.http.HttpTraceAutoConfiguration"
73 = "org.springframework.boot.actuate.autoconfigure.trace.http.HttpTraceEndpointAutoConfiguration"
74 = "org.springframework.boot.actuate.autoconfigure.web.mappings.MappingsEndpointAutoConfiguration"
75 = "org.springframework.boot.actuate.autoconfigure.web.server.ManagementContextAutoConfiguration"
76 = "org.springframework.boot.actuate.autoconfigure.web.servlet.ServletManagementContextAutoConfiguration"
77 = "org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration"
最后调用group.selectImports()，进行排序，主要是根据自动化配置类上的AutoConfigureBefore，AutoConfigureAfter，对顺序进行调整
private static class AutoConfigurationGroup
implements DeferredImportSelector.Group, BeanClassLoaderAware, BeanFactoryAware, ResourceLoaderAware {
private final Map entries = new LinkedHashMap<>();
private final List autoConfigurationEntries = new ArrayList<>();
private ClassLoader beanClassLoader;
private BeanFactory beanFactory;
private ResourceLoader resourceLoader;
private AutoConfigurationMetadata autoConfigurationMetadata;
@Override
public Iterable selectImports() {
if (this.autoConfigurationEntries.isEmpty()) {
return Collections.emptyList();
}
Set allExclusions = this.autoConfigurationEntries.stream()
.map(AutoConfigurationEntry::getExclusions).flatMap(Collection::stream).collect(Collectors.toSet());
Set processedConfigurations = this.autoConfigurationEntries.stream()
.map(AutoConfigurationEntry::getConfigurations).flatMap(Collection::stream)
.collect(Collectors.toCollection(LinkedHashSet::new));
processedConfigurations.removeAll(allExclusions);
// 排序
return sortAutoConfigurations(processedConfigurations, getAutoConfigurationMetadata()).stream()
.map((importClassName) -> new Entry(this.entries.get(importClassName), importClassName))
.collect(Collectors.toList());
}
private List sortAutoConfigurations(Set configurations,
AutoConfigurationMetadata autoConfigurationMetadata) {
return new AutoConfigurationSorter(getMetadataReaderFactory(), autoConfigurationMetadata)
.getInPriorityOrder(configurations);
}
排好序后，每个配置类按照processImports()进一步处理，如果是普通的自动化配置类，会走processConfigurationClass，则需要其上的条件满足加到configurationClasses，才可通过importBy注册到bean definition中。据此，自动化配置导入了大量的配置bean。配置类的条件也会进行过滤。
6.2 ConditionalOnClass实现机制
这里以WebSocketServletAutoConfiguration这个自动化配置类的处理为例。满足条件后，会先处理其内部类。假设处理到JettyWebSocketConfiguration。
@ConditionalOnClass使用常量还是class都没有问题，编译时依赖使用的是optional，能通过编译，但是不会引入依赖。底层bean条件注册使用的是ASM扫描字节码实现的，并不会加载class。
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ Servlet.class, ServerContainer.class })
@ConditionalOnWebApplication(type = Type.SERVLET)
@AutoConfigureBefore(ServletWebServerFactoryAutoConfiguration.class)
public class WebSocketServletAutoConfiguration {
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(WebSocketServerContainerInitializer.class)
static class JettyWebSocketConfiguration {
@Bean
@ConditionalOnMissingBean(name = "websocketServletWebServerCustomizer")
JettyWebSocketServletWebServerCustomizer websocketServletWebServerCustomizer() {
return new JettyWebSocketServletWebServerCustomizer();
}
}
}
可以看到，这里读取的WebSocketServletAutoConfiguration，metadata类型为SimpleAnnotationMetadata，底层使用的是ASM读取的类文件，所以并没有触发类加载。对于内部类，底层使用的也同样是SimpleMetadataReader进行读取，最终也会使用processConfigurationClass进行处理，且在构建ConfigurationClass时，使用了importBy为其外部类
new ConfigurationClass((MetadataReader) this.source, importedBy);
在processConfigurationClass中，首先看该配置类是否满足条件，阶段为PARSE_CONFIGURATION。这里JettyWebSocketConfiguration依赖WebSocketServerContainerInitializer类存在，由于不存在，所以是不生效的，但是这里并不会报错，因为底层实现conditionalOnClass时，没有使用类加载
public boolean shouldSkip(@Nullable AnnotatedTypeMetadata metadata, @Nullable ConfigurationPhase phase) {
if (metadata == null || !metadata.isAnnotated(Conditional.class.getName())) {
return false;
}
if (phase == null) {
if (metadata instanceof AnnotationMetadata &&
ConfigurationClassUtils.isConfigurationCandidate((AnnotationMetadata) metadata)) {
return shouldSkip(metadata, ConfigurationPhase.PARSE_CONFIGURATION);
}
return shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN);
}
List conditions = new ArrayList<>();
// 找到条件类，例如@Conditional(OnClassCondition.class)，返回OnClassCondition类全名，且是字符串，
for (String[] conditionClasses : getConditionClasses(metadata)) {
for (String conditionClass : conditionClasses) {
// 用对应classloader，加载OnClassCondition
Condition condition = getCondition(conditionClass, this.context.getClassLoader());
conditions.add(condition);
}
}
AnnotationAwareOrderComparator.sort(conditions);
for (Condition condition : conditions) {
ConfigurationPhase requiredPhase = null;
if (condition instanceof ConfigurationCondition) {
requiredPhase = ((ConfigurationCondition) condition).getConfigurationPhase();
}
// 对每个conditional接口，传递其所在类的metadata，方便拿到conditional注解上的内容，例如这里是class
if ((requiredPhase == null || requiredPhase == phase) && !condition.matches(this.context, metadata)) {
return true;
}
}
return false;
}
如下，onClassCondition实现时，会从注解所在类metadata，拿到注解字段，这里就是onClasses字段，属性值为org.eclipse.jetty.websocket.jsr356.server.deploy.WebSocketServerContainerInitializer
// ConditionalOnClass
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
ClassLoader classLoader = context.getClassLoader();
ConditionMessage matchMessage = ConditionMessage.empty();
List onClasses = getCandidates(metadata, ConditionalOnClass.class);
if (onClasses != null) {
List missing = filter(onClasses, ClassNameFilter.MISSING, classLoader);
if (!missing.isEmpty()) {
return ConditionOutcome.noMatch(ConditionMessage.forCondition(ConditionalOnClass.class)
.didNotFind("required class", "required classes").items(Style.QUOTE, missing));
}
matchMessage = matchMessage.andCondition(ConditionalOnClass.class)
.found("required class", "required classes")
.items(Style.QUOTE, filter(onClasses, ClassNameFilter.PRESENT, classLoader));
}
List onMissingClasses = getCandidates(metadata, ConditionalOnMissingClass.class);
if (onMissingClasses != null) {
List present = filter(onMissingClasses, ClassNameFilter.PRESENT, classLoader);
if (!present.isEmpty()) {
return ConditionOutcome.noMatch(ConditionMessage.forCondition(ConditionalOnMissingClass.class)
.found("unwanted class", "unwanted classes").items(Style.QUOTE, present));
}
matchMessage = matchMessage.andCondition(ConditionalOnMissingClass.class)
.didNotFind("unwanted class", "unwanted classes")
.items(Style.QUOTE, filter(onMissingClasses, ClassNameFilter.MISSING, classLoader));
}
return ConditionOutcome.match(matchMessage);
}
private List getCandidates(AnnotatedTypeMetadata metadata, Class annotationType) {
// classValuesAsString=true，表示注解上的类，以字符串表示，不要load class
MultiValueMap attributes = metadata.getAllAnnotationAttributes(annotationType.getName(), true);
if (attributes == null) {
return null;
}
List candidates = new ArrayList<>();
addAll(candidates, attributes.get("value"));
addAll(candidates, attributes.get("name"));
return candidates;
}
最终底层会用Class.forName(className, false, classloader);尝试加载类，不抛出异常则表示存在，否则类不存在。
6.3 ConditionalOnMissingBean实现机制
这里还是以WebSocketServletAutoConfiguration为例，本实例中TomcatWebSocketConfiguration是生效的，看看里面的conditionalOnMissingBean如何实现：
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ Servlet.class, ServerContainer.class })
@ConditionalOnWebApplication(type = Type.SERVLET)
@AutoConfigureBefore(ServletWebServerFactoryAutoConfiguration.class)
public class WebSocketServletAutoConfiguration {
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ Tomcat.class, WsSci.class })
static class TomcatWebSocketConfiguration {
@Bean
@ConditionalOnMissingBean(name = "websocketServletWebServerCustomizer")
TomcatWebSocketServletWebServerCustomizer websocketServletWebServerCustomizer() {
return new TomcatWebSocketServletWebServerCustomizer();
}
}
在处理@Bean方法时，不会处理其上的条件，会添加到ConfigurationClass中。
当这一批处理自动化配置类后，会调用loadBeanDefinitions
this.reader.loadBeanDefinitions(configClasses);
对于自动化配置类，由于是导进来的，这里会手动注册配置类到BeanDefinitionRegistry，
然后加载bean method，判断是否符合条件，注册bean definition。注意，这个阶段是ConfigurationPhase.REGISTER_BEAN
// org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader#loadBeanDefinitionsForBeanMethod
private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
ConfigurationClass configClass = beanMethod.getConfigurationClass();
MethodMetadata metadata = beanMethod.getMetadata();
String methodName = metadata.getMethodName();
// 判断这个方法对应的bean是否能够注册成bean。
// Do we need to mark the bean as skipped by its condition?
if (this.conditionEvaluator.shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN)) {
configClass.skippedBeanMethods.add(methodName);
return;
}
if (configClass.skippedBeanMethods.contains(methodName)) {
return;
}
AnnotationAttributes bean = AnnotationConfigUtils.attributesFor(metadata, Bean.class);
Assert.state(bean != null, "No @Bean annotation attributes");
// Consider name and any aliases
List names = new ArrayList<>(Arrays.asList(bean.getStringArray("name")));
String beanName = (!names.isEmpty() ? names.remove(0) : methodName);
// Register aliases even when overridden
for (String alias : names) {
this.registry.registerAlias(beanName, alias);
}
// Has this effectively been overridden before (e.g. via XML)?
if (isOverriddenByExistingDefinition(beanMethod, beanName)) {
if (beanName.equals(beanMethod.getConfigurationClass().getBeanName())) {
throw new BeanDefinitionStoreException(beanMethod.getConfigurationClass().getResource().getDescription(),
beanName, "Bean name derived from @Bean method '" + beanMethod.getMetadata().getMethodName() +
"' clashes with bean name for containing configuration class; please make those names unique!");
}
return;
}
ConfigurationClassBeanDefinition beanDef = new ConfigurationClassBeanDefinition(configClass, metadata, beanName);
beanDef.setSource(this.sourceExtractor.extractSource(metadata, configClass.getResource()));
// 如果是静态方法，则bean class则是配置类所在的class
if (metadata.isStatic()) {
// static @Bean method
if (configClass.getMetadata() instanceof StandardAnnotationMetadata) {
beanDef.setBeanClass(((StandardAnnotationMetadata) configClass.getMetadata()).getIntrospectedClass());
}
else {
beanDef.setBeanClassName(configClass.getMetadata().getClassName());
}
beanDef.setUniqueFactoryMethodName(methodName);
}
else {
// 如果是实例方法，则bean class为空，会设置factoryBeanName为配置类的bean name
// instance @Bean method
beanDef.setFactoryBeanName(configClass.getBeanName());
beanDef.setUniqueFactoryMethodName(methodName);
}
if (metadata instanceof StandardMethodMetadata) {
beanDef.setResolvedFactoryMethod(((StandardMethodMetadata) metadata).getIntrospectedMethod());
}
beanDef.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR);
beanDef.setAttribute(org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor.
SKIP_REQUIRED_CHECK_ATTRIBUTE, Boolean.TRUE);
AnnotationConfigUtils.processCommonDefinitionAnnotations(beanDef, metadata);
Autowire autowire = bean.getEnum("autowire");
if (autowire.isAutowire()) {
beanDef.setAutowireMode(autowire.value());
}
boolean autowireCandidate = bean.getBoolean("autowireCandidate");
if (!autowireCandidate) {
beanDef.setAutowireCandidate(false);
}
String initMethodName = bean.getString("initMethod");
if (StringUtils.hasText(initMethodName)) {
beanDef.setInitMethodName(initMethodName);
}
String destroyMethodName = bean.getString("destroyMethod");
beanDef.setDestroyMethodName(destroyMethodName);
// Consider scoping
ScopedProxyMode proxyMode = ScopedProxyMode.NO;
AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(metadata, Scope.class);
if (attributes != null) {
beanDef.setScope(attributes.getString("value"));
proxyMode = attributes.getEnum("proxyMode");
if (proxyMode == ScopedProxyMode.DEFAULT) {
proxyMode = ScopedProxyMode.NO;
}
}
// Replace the original bean definition with the target one, if necessary
BeanDefinition beanDefToRegister = beanDef;
if (proxyMode != ScopedProxyMode.NO) {
BeanDefinitionHolder proxyDef = ScopedProxyCreator.createScopedProxy(
new BeanDefinitionHolder(beanDef, beanName), this.registry,
proxyMode == ScopedProxyMode.TARGET_CLASS);
beanDefToRegister = new ConfigurationClassBeanDefinition(
(RootBeanDefinition) proxyDef.getBeanDefinition(), configClass, metadata, beanName);
}
if (logger.isTraceEnabled()) {
logger.trace(String.format("Registering bean definition for @Bean method %s.%s()",
configClass.getMetadata().getClassName(), beanName));
}
this.registry.registerBeanDefinition(beanName, beanDefToRegister);
}
@ConditionalOnMissingBean可以控制从哪个容器查找，默认是ALL，也就是当前容器和所有父容器，也可以是当前spring容器，或者是所有祖先容器。
- ConditionalOnMissingBean需要确保扫描的先后顺序，不同的自动配置类，需要通过@AutoConfigureBefore/@AutoConfigureAfter来指定先后顺序，否则可能其他自动配置类先扫描到，先注入到BeanDefinitionRegistry了，后面的就不生效了。保证扫描顺序。同一个类下面的两个内部类，可以通过@Order来区分。
- 依赖其他配置先注入，否则可能注入两个相同的类的bean。
另外，当类型和beanName均没有设置值时，默认按照返回值类型进行匹配，会加载返回值class
6.4 @Bean方法bean name已经存在覆盖机制
- 对于两个均为java config @Bean，beanName已经存在了，对于同一个类文件，方法名一样时（方法重载），以最开始的为准，这个时候会设置setNonUniqueFactoryMethodName；不同类文件，以后续的为主
- @Bean和@Component beanName一样时，@Bean优先
- 基础角色会覆盖用户定义的
- 未开启overriding，则会抛出异常，开启了则以开始的为准，先到先得
protected boolean isOverriddenByExistingDefinition(BeanMethod beanMethod, String beanName) {
if (!this.registry.containsBeanDefinition(beanName)) {
return false;
}
BeanDefinition existingBeanDef = this.registry.getBeanDefinition(beanName);
// Is the existing bean definition one that was created from a configuration class?
// -> allow the current bean method to override, since both are at second-pass level.
// However, if the bean method is an overloaded case on the same configuration class,
// preserve the existing bean definition.
if (existingBeanDef instanceof ConfigurationClassBeanDefinition) {
ConfigurationClassBeanDefinition ccbd = (ConfigurationClassBeanDefinition) existingBeanDef;
// 对于java config @Bean，beanName已经存在了，对于同一个类文件，方法名一样时，以最开始的为准，不同类文件，以后续的为主
if (ccbd.getMetadata().getClassName().equals(
beanMethod.getConfigurationClass().getMetadata().getClassName())) {
if (ccbd.getFactoryMethodMetadata().getMethodName().equals(ccbd.getFactoryMethodName())) {
ccbd.setNonUniqueFactoryMethodName(ccbd.getFactoryMethodMetadata().getMethodName());
}
return true;
}
else {
return false;
}
}
// A bean definition resulting from a component scan can be silently overridden
// by an @Bean method, as of 4.2...
// @Bean和@Component beanName一样时，@Bean优先
if (existingBeanDef instanceof ScannedGenericBeanDefinition) {
return false;
}
// 基础角色会覆盖用户定义的
// Has the existing bean definition bean marked as a framework-generated bean?
// -> allow the current bean method to override it, since it is application-level
if (existingBeanDef.getRole() > BeanDefinition.ROLE_APPLICATION) {
return false;
}
// At this point, it's a top-level override (probably XML), just having been parsed
// before configuration class processing kicks in...
if (this.registry instanceof DefaultListableBeanFactory &&
!((DefaultListableBeanFactory) this.registry).isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionStoreException(beanMethod.getConfigurationClass().getResource().getDescription(),
beanName, "@Bean definition illegally overridden by existing bean definition: " + existingBeanDef);
}
return true;
}
6.5 @Bean definition表示
注册bean definition为ConfigurationClassBeanDefinition，均会设置setUniqueFactoryMethodName为方法名。注意，这里的fatoryBean和fatoryMethod，跟实现FactoryBean接口的不是一个意思，需要区别对待。
- 如果是静态方法，则bean class则是配置类所在的class，不依赖配置类实例化bean。
- 如果是实例方法，则bean class为空，会设置factoryBeanName为配置类的bean name，依赖配置类先初始化为完整的bean。然后再调用该方法进行初始化构造@Bean
6.6 注册管家注入bean
本实例中，MybatisAutoConfiguration会生效，但是没有使用注解MapperScan，所以内嵌类MapperScannerRegistrarNotFoundConfiguration条件生效，进而在处理该内部类时，会导入AutoConfiguredMapperScannerRegistrar，其实现了ImportBeanDefinitionRegistrar
@org.springframework.context.annotation.Configuration
@ConditionalOnClass({ SqlSessionFactory.class, SqlSessionFactoryBean.class })
@ConditionalOnBean(DataSource.class)
@EnableConfigurationProperties(MybatisProperties.class)
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
public class MybatisAutoConfiguration {
private static final Logger logger = LoggerFactory.getLogger(MybatisAutoConfiguration.class);
private final MybatisProperties properties;
private final Interceptor[] interceptors;
private final ResourceLoader resourceLoader;
private final DatabaseIdProvider databaseIdProvider;
private final List configurationCustomizers;
public MybatisAutoConfiguration(MybatisProperties properties,
ObjectProvider interceptorsProvider,
ResourceLoader resourceLoader,
ObjectProvider databaseIdProvider,
ObjectProvider> configurationCustomizersProvider) {
this.properties = properties;
this.interceptors = interceptorsProvider.getIfAvailable();
this.resourceLoader = resourceLoader;
this.databaseIdProvider = databaseIdProvider.getIfAvailable();
this.configurationCustomizers = configurationCustomizersProvider.getIfAvailable();
}
@PostConstruct
public void checkConfigFileExists() {
if (this.properties.isCheckConfigLocation() && StringUtils.hasText(this.properties.getConfigLocation())) {
Resource resource = this.resourceLoader.getResource(this.properties.getConfigLocation());
Assert.state(resource.exists(), "Cannot find config location: " + resource
+ " (please add config file or check your Mybatis configuration)");
}
}
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
SqlSessionFactoryBean factory = new SqlSessionFactoryBean();
factory.setDataSource(dataSource);
factory.setVfs(SpringBootVFS.class);
if (StringUtils.hasText(this.properties.getConfigLocation())) {
factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation()));
}
Configuration configuration = this.properties.getConfiguration();
if (configuration == null && !StringUtils.hasText(this.properties.getConfigLocation())) {
configuration = new Configuration();
}
if (configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) {
for (ConfigurationCustomizer customizer : this.configurationCustomizers) {
customizer.customize(configuration);
}
}
factory.setConfiguration(configuration);
if (this.properties.getConfigurationProperties() != null) {
factory.setConfigurationProperties(this.properties.getConfigurationProperties());
}
if (!ObjectUtils.isEmpty(this.interceptors)) {
factory.setPlugins(this.interceptors);
}
if (this.databaseIdProvider != null) {
factory.setDatabaseIdProvider(this.databaseIdProvider);
}
if (StringUtils.hasLength(this.properties.getTypeAliasesPackage())) {
factory.setTypeAliasesPackage(this.properties.getTypeAliasesPackage());
}
if (StringUtils.hasLength(this.properties.getTypeHandlersPackage())) {
factory.setTypeHandlersPackage(this.properties.getTypeHandlersPackage());
}
if (!ObjectUtils.isEmpty(this.properties.resolveMapperLocations())) {
factory.setMapperLocations(this.properties.resolveMapperLocations());
}
return factory.getObject();
}
@Bean
@ConditionalOnMissingBean
public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
ExecutorType executorType = this.properties.getExecutorType();
if (executorType != null) {
return new SqlSessionTemplate(sqlSessionFactory, executorType);
} else {
return new SqlSessionTemplate(sqlSessionFactory);
}
}
/**
* This will just scan the same base package as Spring Boot does. If you want
* more power, you can explicitly use
* {@link org.mybatis.spring.annotation.MapperScan} but this will get typed
* mappers working correctly, out-of-the-box, similar to using Spring Data JPA
* repositories.
*/
public static class AutoConfiguredMapperScannerRegistrar
implements BeanFactoryAware, ImportBeanDefinitionRegistrar, ResourceLoaderAware {
private BeanFactory beanFactory;
private ResourceLoader resourceLoader;
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
logger.debug("Searching for mappers annotated with @Mapper");
ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
try {
if (this.resourceLoader != null) {
scanner.setResourceLoader(this.resourceLoader);
}
List packages = AutoConfigurationPackages.get(this.beanFactory);
if (logger.isDebugEnabled()) {
for (String pkg : packages) {
logger.debug("Using auto-configuration base package '{}'", pkg);
}
}
scanner.setAnnotationClass(Mapper.class);
scanner.registerFilters();
scanner.doScan(StringUtils.toStringArray(packages));
} catch (IllegalStateException ex) {
logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled.", ex);
}
}
@Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
this.beanFactory = beanFactory;
}
@Override
public void setResourceLoader(ResourceLoader resourceLoader) {
this.resourceLoader = resourceLoader;
}
}
/**
* {@link org.mybatis.spring.annotation.MapperScan} ultimately ends up
* creating instances of {@link MapperFactoryBean}. If
* {@link org.mybatis.spring.annotation.MapperScan} is used then this
* auto-configuration is not needed. If it is _not_ used, however, then this
* will bring in a bean registrar and automatically register components based
* on the same component-scanning path as Spring Boot itself.
*/
@org.springframework.context.annotation.Configuration
@Import({ AutoConfiguredMapperScannerRegistrar.class })
@ConditionalOnMissingBean(MapperFactoryBean.class)
public static class MapperScannerRegistrarNotFoundConfiguration {
@PostConstruct
public void afterPropertiesSet() {
logger.debug("No {} found.", MapperFactoryBean.class.getName());
}
}
}
AutoConfiguredMapperScannerRegistrar主要是扫描@Mapper接口，注入数据库mapper对象。默认扫描的包，就是@EnableAutoConfiguration指定的包，没有指定的话，默认就是main类所在的包
public static class AutoConfiguredMapperScannerRegistrar
implements BeanFactoryAware, ImportBeanDefinitionRegistrar, ResourceLoaderAware {
private BeanFactory beanFactory;
private ResourceLoader resourceLoader;
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
logger.debug("Searching for mappers annotated with @Mapper");
//扫描@Mapper接口，注入数据库mapper对象。
ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
try {
if (this.resourceLoader != null) {
scanner.setResourceLoader(this.resourceLoader);
}
// 默认扫描的包，就是@EnableAutoConfiguration指定的包，没有指定的话，默认就是main类所在的包
List packages = AutoConfigurationPackages.get(this.beanFactory);
if (logger.isDebugEnabled()) {
for (String pkg : packages) {
logger.debug("Using auto-configuration base package '{}'", pkg);
}
}
scanner.setAnnotationClass(Mapper.class);
scanner.registerFilters();
scanner.doScan(StringUtils.toStringArray(packages));
} catch (IllegalStateException ex) {
logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled.", ex);
}
}
6.7 EnableXXX机制
Spring框架提供的各种名字为@Enable开头的Annotation定义，比如@EnableScheduling、@EnableCaching、@EnableMBeanExport、@EableAsync、@EnableTransactionManagement、@EnableAspectJAutoProxy等，
- @EnableScheduling是通过@Import将Spring调度框架相关的bean定义都加载到IoC容器。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(SchedulingConfiguration.class)
@Documented
public @interface EnableScheduling {
}
@Configuration(proxyBeanMethods = false)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public class SchedulingConfiguration {
@Bean(name = TaskManagementConfigUtils.SCHEDULED_ANNOTATION_PROCESSOR_BEAN_NAME)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public ScheduledAnnotationBeanPostProcessor scheduledAnnotationProcessor() {
return new ScheduledAnnotationBeanPostProcessor();
}
}
- EnableCaching，借助ImportSelector来加载class name
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(CachingConfigurationSelector.class)
public @interface EnableCaching {
}
- EnableAspectJAutoProxy通过注册管家注入proxy相关后处理器
@Import(AspectJAutoProxyRegistrar.class)
public @interface EnableAspectJAutoProxy {
这些与@EnableAutoConfiguration的理念和做事方式其实一脉相承，都是借助@Import的支持，收集和注册特定场景相关的bean定义
7. 处理sourceClass的注解ImportResource和@Bean方法
处理sourceClass上的@ImportResource注解，并添加到configClass.addImportedResource
处理sourceClass上的@Bean方法注解，并添加到configClass.addBeanMethod，然后处理sourceClass接口上的@Bean默认方法，添加到configClass.addBeanMethod
8. 注册imported配置类、beanMethod、importResource、registrar
如下，当一批配置类处理结束后，获取到所有put到configurationClasses这个map的configuration class，处理并注册到BeanDefinitionRegistry中。
这个时候对应的阶段为REGISTER_BEAN，在这个阶段生效的条件，将会再对配置类进行过滤。实现了ConfigurationCondition，且指定了REGISTER_BEAN的注解，只在这个阶段生效，例如ConditionalOnBean
- 对被导入的类，如内部类，通过@EnableAutoConfiguration导入的类，注册到BeanDefinitionRegistry
- 处理BeanMethod，这个阶段才会对其上的条件注解进行解析，生效才注册到BeanDefinitionRegistry
- 对importResource，使用BeanDefinitionReader进行读取，解析为BeanDefinition并注册到BeanDefinitionRegistry。
- 对导入的注册管家，调用registrar.registerBeanDefinitions方法，通过方法代码手动将相关beanDefinition注册BeanDefinitionRegistry。
private void loadBeanDefinitionsForConfigurationClass(
ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) {
// 再次判断是否满足条件注解，不满足的直接过滤掉，尤其是指定了REGISTER_BEAN阶段的配置类。
if (trackedConditionEvaluator.shouldSkip(configClass)) {
String beanName = configClass.getBeanName();
if (StringUtils.hasLength(beanName) && this.registry.containsBeanDefinition(beanName)) {
this.registry.removeBeanDefinition(beanName);
}
this.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());
return;
}
// 注册imported类
if (configClass.isImported()) {
registerBeanDefinitionForImportedConfigurationClass(configClass);
}
//
for (BeanMethod beanMethod : configClass.getBeanMethods()) {
loadBeanDefinitionsForBeanMethod(beanMethod);
}
loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
}
9. full模式配置类生成cglib代理
在ConfigurationClassPostProcessor的postProcessBeanFactory阶段，大模式或者非注解或者有@Bean方法，会提前加载该配置类到JVM，会对所有full模式的配置类进行cglib增强，并添加ImportAwareBeanPostProcessor。
为什么要进行cglib增强？主要是为了对@Bean方法里的内部调用进行代理，保证使用的是单例的bean，而不是生成不一样的引用。这个也是@Configuration和@Component的主要区别。如果没有内部方法调用，可以配置proxyMethod=false，避免生成过多的代理类。
// org.springframework.context.annotation.ConfigurationClassPostProcessor#postProcessBeanFactory
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
int factoryId = System.identityHashCode(beanFactory);
if (this.factoriesPostProcessed.contains(factoryId)) {
throw new IllegalStateException(
"postProcessBeanFactory already called on this post-processor against " + beanFactory);
}
this.factoriesPostProcessed.add(factoryId);
if (!this.registriesPostProcessed.contains(factoryId)) {
// BeanDefinitionRegistryPostProcessor hook apparently not supported...
// Simply call processConfigurationClasses lazily at this point then.
processConfigBeanDefinitions((BeanDefinitionRegistry) beanFactory);
}
enhanceConfigurationClasses(beanFactory);
beanFactory.addBeanPostProcessor(new ImportAwareBeanPostProcessor(beanFactory));
}
public void enhanceConfigurationClasses(ConfigurableListableBeanFactory beanFactory) {
StartupStep enhanceConfigClasses = this.applicationStartup.start("spring.context.config-classes.enhance");
Map configBeanDefs = new LinkedHashMap<>();
for (String beanName : beanFactory.getBeanDefinitionNames()) {
BeanDefinition beanDef = beanFactory.getBeanDefinition(beanName);
// 获取到配置模式
Object configClassAttr = beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE);
AnnotationMetadata annotationMetadata = null;
MethodMetadata methodMetadata = null;
if (beanDef instanceof AnnotatedBeanDefinition) {
AnnotatedBeanDefinition annotatedBeanDefinition = (AnnotatedBeanDefinition) beanDef;
annotationMetadata = annotatedBeanDefinition.getMetadata();
methodMetadata = annotatedBeanDefinition.getFactoryMethodMetadata();
}
if ((configClassAttr != null || methodMetadata != null) && beanDef instanceof AbstractBeanDefinition) {
// Configuration class (full or lite) or a configuration-derived @Bean method
// -> eagerly resolve bean class at this point, unless it's a 'lite' configuration
// or component class without @Bean methods.
AbstractBeanDefinition abd = (AbstractBeanDefinition) beanDef;
if (!abd.hasBeanClass()) {
// 大模式或者非注解或者有@Bean方法，会提前加载该配置类到jvm
boolean liteConfigurationCandidateWithoutBeanMethods =
(ConfigurationClassUtils.CONFIGURATION_CLASS_LITE.equals(configClassAttr) &&
annotationMetadata != null && !ConfigurationClassUtils.hasBeanMethods(annotationMetadata));
if (!liteConfigurationCandidateWithoutBeanMethods) {
try {
abd.resolveBeanClass(this.beanClassLoader);
}
catch (Throwable ex) {
throw new IllegalStateException(
"Cannot load configuration class: " + beanDef.getBeanClassName(), ex);
}
}
}
}
if (ConfigurationClassUtils.CONFIGURATION_CLASS_FULL.equals(configClassAttr)) {
if (!(beanDef instanceof AbstractBeanDefinition)) {
throw new BeanDefinitionStoreException("Cannot enhance @Configuration bean definition '" +
beanName + "' since it is not stored in an AbstractBeanDefinition subclass");
}
else if (logger.isInfoEnabled() && beanFactory.containsSingleton(beanName)) {
logger.info("Cannot enhance @Configuration bean definition '" + beanName +
"' since its singleton instance has been created too early. The typical cause " +
"is a non-static @Bean method with a BeanDefinitionRegistryPostProcessor " +
"return type: Consider declaring such methods as 'static'.");
}
// 只处理大模式
configBeanDefs.put(beanName, (AbstractBeanDefinition) beanDef);
}
}
if (configBeanDefs.isEmpty() || NativeDetector.inNativeImage()) {
// nothing to enhance -> return immediately
enhanceConfigClasses.end();
return;
}
ConfigurationClassEnhancer enhancer = new ConfigurationClassEnhancer();
for (Map.Entry entry : configBeanDefs.entrySet()) {
AbstractBeanDefinition beanDef = entry.getValue();
// If a @Configuration class gets proxied, always proxy the target class
beanDef.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
// Set enhanced subclass of the user-specified bean class
Class configClass = beanDef.getBeanClass();
Class enhancedClass = enhancer.enhance(configClass, this.beanClassLoader);
if (configClass != enhancedClass) {
if (logger.isTraceEnabled()) {
logger.trace(String.format("Replacing bean definition '%s' existing class '%s' with " +
"enhanced class '%s'", entry.getKey(), configClass.getName(), enhancedClass.getName()));
}
// 对配置类进行cglib增强，替换掉bean class
beanDef.setBeanClass(enhancedClass);
}
}
enhanceConfigClasses.tag("classCount", () -> String.valueOf(configBeanDefs.keySet().size())).end();
}
ImportAwareBeanPostProcessor主要有两个作用，一个是对所有cglib增强的配置类，注入beanFactory，方便内部方法调用时，利用该beanFactory查找bean；另一个是设置每个实现了ImportAware的bean的导入类，如果有导入类的话。
private static class ImportAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor {
private final BeanFactory beanFactory;
public ImportAwareBeanPostProcessor(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
@Override
public PropertyValues postProcessProperties(@Nullable PropertyValues pvs, Object bean, String beanName) {
// Inject the BeanFactory before AutowiredAnnotationBeanPostProcessor's
// postProcessProperties method attempts to autowire other configuration beans.
if (bean instanceof EnhancedConfiguration) {
((EnhancedConfiguration) bean).setBeanFactory(this.beanFactory);
}
return pvs;
}
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) {
if (bean instanceof ImportAware) {
ImportRegistry ir = this.beanFactory.getBean(IMPORT_REGISTRY_BEAN_NAME, ImportRegistry.class);
AnnotationMetadata importingClass = ir.getImportingClassFor(ClassUtils.getUserClass(bean).getName());
if (importingClass != null) {
((ImportAware) bean).setImportMetadata(importingClass);
}
}
return bean;
}
}