『SpringBoot 源码分析』run() 方法执行流程:(3)刷新应用上下文-处理 @ComponentScan 注解
- 基于 2.2.9.RELEASE
- 问题:当方法进行了注释标记之后,springboot 又是怎么注入到容器中并创建类呢?
- 首先创建测试主程序
java
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package com.lagou;
@SpringBootApplication//标注在类上说明这个类是`SpringBoot`的主配置类
public class SpringBootMytestApplication{
public static void main(String[] args) {
SpringApplication.run(SpringBootMytestApplication.class, args);
}
}
- 创建测试 Controller
java
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package com.lagou.controller;
@RestController
public class TestController {
@RequestMapping("/test")
public String test(){
System.out.println("源码环境构建成功...");
return "源码环境构建成功";
}
}
处理 @ComponentScan 注解
- 准备好上下文以及上下文环境之后,可以继续来看看 springboot 究竟是如何把主类所在的类路径下相关的类通过 @ComponentScan 注册到 IOC 容器中。首先先走到 refreshContext() 方法,然后调用 ApplicationContext 的 refresh()
java
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public class SpringApplication {
...
public ConfigurableApplicationContext run(String... args) {
...
try {
// 将运行时参数封装
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
// 构造应用上下文环境
ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
// 处理需要忽略的 Bean
configureIgnoreBeanInfo(environment);
// 打印 banner
Banner printedBanner = printBanner(environment);
// 刷新应用上下文前的准备阶段
context = createApplicationContext();
// 实例化 SpringBootExceptionReporter.class,用来支持报告关于启动的错误
exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
new Class[] { ConfigurableApplicationContext.class }, context);
// 刷新应用上下文前的准备阶段
prepareContext(context, environment, listeners, applicationArguments, printedBanner);
// 1. 刷新应用上下文
refreshContext(context);
...
}
catch (Throwable ex) {
...
}
...
}
protected void refresh(ApplicationContext applicationContext) {
Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext);
// 2. spring 的核心方法,刷新上下文
((AbstractApplicationContext) applicationContext).refresh();
}
}
- 接着 ApplicationContext 调用父类的 refresh()
java
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public class ServletWebServerApplicationContext extends GenericWebApplicationContext
implements ConfigurableWebServerApplicationContext {
...
@Override
public final void refresh() throws BeansException, IllegalStateException {
try {
// 1. 调用父类 refresh() 方法
super.refresh();
}
catch (RuntimeException ex) {
stopAndReleaseWebServer();
throw ex;
}
}
}
- 在 refresh() 中,首先对上下文进行预处理,设置一些必要的参数,然后获取 IOC 容器,并对 IOC 容器进行一些参数进行设置,然后调用工厂处理器注册相关的 bean 进入上下文
java
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public abstract class AbstractApplicationContext extends DefaultResourceLoader
implements ConfigurableApplicationContext {
private final Object startupShutdownMonitor = new Object();
...
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 1. 上下文设置一些必要的参数
prepareRefresh();
// 2. 获取 IOC 容器
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 3. 对 IOC 容器进行一些参数设置
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// 4. 调用工厂处理器,注册 bean 到 IOC 容器
invokeBeanFactoryPostProcessors(beanFactory);
...
} catch (BeansException ex) {
...
}
...
}
}
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 5. 对 IOC 容器调用 beanFactoryPostProcessors 来处理
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
}
- 通过后置处理器注册的委派类 PostProcessorRegistrationDelegate 调用 invokeBeanFactoryPostProcessors() 的逻辑相对复杂一些,我们直接跳过,只关注问题本身,走到下面的一句话
java
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final class PostProcessorRegistrationDelegate {
...
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
regularPostProcessors.add(postProcessor);
}
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// Separate between BeanDefinitionRegistryPostProcessors that implement
// PriorityOrdered, Ordered, and the rest.
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 1. 调用 bean 注册处理器,处理类的注册
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
...
}
...
}
private static void invokeBeanDefinitionRegistryPostProcessors(
Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
// 2. 其中 postProcessors 只有一个类,即为 ConfigurationClassPostProcessor
postProcessor.postProcessBeanDefinitionRegistry(registry);
}
}
}
- 其中,配置类最关键的对象是 ConfigurationClassPostProcessor 后置处理器
- 这时候就会交由 ConfigurationClassPostProcessor 来注册 bean 到 IOC 容器中
java
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public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,
PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {
private final Set<Integer> registriesPostProcessed = new HashSet<>();
...
@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);
// 1. 注册 bean 到 IOC 容器中
processConfigBeanDefinitions(registry);
}
}
- 当调用 processConfigBeanDefinitions() 时,首先会创建 ConfigurationClassParser 用于解析 @Configuration
java
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public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,
PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {
private MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory();
private ProblemReporter problemReporter = new FailFastProblemReporter();
@Nullable
private Environment environment;
private ResourceLoader resourceLoader = new DefaultResourceLoader();
private BeanNameGenerator componentScanBeanNameGenerator = AnnotationBeanNameGenerator.INSTANCE;
...
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
String[] candidateNames = registry.getBeanDefinitionNames();
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);
}
}
// 把主类封装进 BeanDefinitionHolder 中
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();
}
// 1. 创建解析器,用于解析 @Configuration 标注的类
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
do {
// 2. 开始解析候选类
parser.parse(candidates);
...
}
while (!candidates.isEmpty());
...
}
}
- 其中,这里的 candidates 属性也就只有主类
- 接下来会遍历 candidates 属性,解析主类的注解
java
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class ConfigurationClassParser {
private static final Predicate<String> DEFAULT_EXCLUSION_FILTER = className ->
(className.startsWith("java.lang.annotation.") || className.startsWith("org.springframework.stereotype."));
...
public void parse(Set<BeanDefinitionHolder> configCandidates) {
for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
try {
if (bd instanceof AnnotatedBeanDefinition) {
// 1. 解析主类配置,其中 getBeanName() 为 SpringBootMytestApplication
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();
}
protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
processConfigurationClass(new ConfigurationClass(metadata, beanName), DEFAULT_EXCLUSION_FILTER);
}
}
- 再走进一层嵌套中,遇到 do 开头的方法,才是真正处理的时候
java
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class ConfigurationClassParser {
...
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 {
// 1. 真正处理 @Configuration 的方法,其中 sourceClass 为 com.lagou.SpringBootMytestApplication
sourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);
}
while (sourceClass != null);
this.configurationClasses.put(configClass, configClass);
}
}
- 接下来会根据不同的注解,执行不同的处理方法,这里主要关注处理 @ComponentScan 注解的位置,首先会判断 sourceClass 是否标注了 @ComponentScan 注解,主类 @SpringBootApplication 是肯定包含这个注解。然后通过 ComponentScanAnnotationParser 来进行解析
java
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class ConfigurationClassParser {
private final ComponentScanAnnotationParser componentScanParser;
private final ConditionEvaluator conditionEvaluator;
private final Environment environment;
...
@Nullable
protected final SourceClass doProcessConfigurationClass(
ConfigurationClass configClass, SourceClass sourceClass, Predicate<String> filter)
throws IOException {
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
// 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");
}
}
// 1. 扫描主类 @ComponentScan 注解里面的配置属性
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) {
// 2. 解析 @ComponentScan 的注解的属性,然后把扫描到的相关类转化为 BeanDefinition
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());
}
}
}
}
...
}
}
- parse() 主体逻辑就是首先创建 ClassPathBeanDefinitionScanner 扫描器,然后判断主类的 @ComponentScan 注解是否标注了 basePackages 属性,没有的话就把主类所在的包放进去,然后扫描所有的 @Component 类,封装成 BeanDefinition
- 重点:所以这里就是为什么主类所在的包,以及其子包的类都能扫出来
java
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class ComponentScanAnnotationParser {
private final BeanNameGenerator beanNameGenerator;
private final ResourceLoader resourceLoader;
private final Environment environment;
private final BeanDefinitionRegistry registry;
...
// declaringClass 为 com.lagou.SpringBootMytestApplication
public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
// 1. 创建 BeanDefinition 扫描器
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);
Class<? extends BeanNameGenerator> generatorClass = componentScan.getClass("nameGenerator");
boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
BeanUtils.instantiateClass(generatorClass));
ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy");
if (scopedProxyMode != ScopedProxyMode.DEFAULT) {
scanner.setScopedProxyMode(scopedProxyMode);
}
else {
Class<? extends ScopeMetadataResolver> resolverClass = componentScan.getClass("scopeResolver");
scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));
}
scanner.setResourcePattern(componentScan.getString("resourcePattern"));
for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addIncludeFilter(typeFilter);
}
}
for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addExcludeFilter(typeFilter);
}
}
boolean lazyInit = componentScan.getBoolean("lazyInit");
if (lazyInit) {
scanner.getBeanDefinitionDefaults().setLazyInit(true);
}
Set<String> basePackages = new LinkedHashSet<>();
// 2. 尝试查看注解有没添加 basePackages 属性
String[] basePackagesArray = componentScan.getStringArray("basePackages");
for (String pkg : basePackagesArray) {
String[] tokenized = StringUtils.tokenizeToStringArray(this.environment.resolvePlaceholders(pkg),
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
Collections.addAll(basePackages, tokenized);
}
for (Class<?> clazz : componentScan.getClassArray("basePackageClasses")) {
basePackages.add(ClassUtils.getPackageName(clazz));
}
if (basePackages.isEmpty()) {
// 3. 没有就获取类所在的包名,这里是 com.lagou
basePackages.add(ClassUtils.getPackageName(declaringClass));
}
scanner.addExcludeFilter(new AbstractTypeHierarchyTraversingFilter(false, false) {
@Override
protected boolean matchClassName(String className) {
return declaringClass.equals(className);
}
});
// 4. 扫描对应的包,把所有相关的 @Component 的类封装成 BeanDefinition 返回
return scanner.doScan(StringUtils.toStringArray(basePackages));
}
}
- 其中,componentScan 包含的相关属性如下
- doScan() 先通过 basePackages 属性,找到所有候选 Components,然后把它们注册到 IOC 容器中并返回
java
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public class ClassPathBeanDefinitionScanner extends ClassPathScanningCandidateComponentProvider {
private final BeanDefinitionRegistry registry;
private BeanNameGenerator beanNameGenerator = AnnotationBeanNameGenerator.INSTANCE;
private ScopeMetadataResolver scopeMetadataResolver = new AnnotationScopeMetadataResolver();
...
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
// 1. basePackages 为 com.lagou
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
for (String basePackage : basePackages) {
// 2. 根据 basePackage 找到所有候选的 Components
Set<BeanDefinition> 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);
// 3. 将候选 Components 注册进 IOC 容器
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
// 4. 返回 beanDefinitions
return beanDefinitions;
}
}
- 其中,findCandidateComponents() 会调用嵌套方法 scanCandidateComponents() 。它会把 basePackage 属性拼接起来,形成 classpath*:com/lagou/**/*.class 路径,扫描所有的类,并返回
java
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public class ClassPathScanningCandidateComponentProvider implements EnvironmentCapable, ResourceLoaderAware {
static final String DEFAULT_RESOURCE_PATTERN = "**/*.class";
private String resourcePattern = DEFAULT_RESOURCE_PATTERN;
...
private Set<BeanDefinition> scanCandidateComponents(String basePackage) {
Set<BeanDefinition> candidates = new LinkedHashSet<>();
try {
// 1. 拼接的路径为 classpath*:com/lagou/**/*.class
String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
resolveBasePackage(basePackage) + '/' + this.resourcePattern;
// 2. 得到已经扫描出来的源
Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath);
boolean traceEnabled = logger.isTraceEnabled();
boolean debugEnabled = logger.isDebugEnabled();
for (Resource resource : resources) {
if (traceEnabled) {
logger.trace("Scanning " + resource);
}
if (resource.isReadable()) {
try {
MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
// 先判断 resource 是不是候选的 component
if (isCandidateComponent(metadataReader)) {
// 封装成通用 BeanDefinition
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
sbd.setSource(resource);
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 (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to read candidate component class: " + resource, ex);
}
}
else {
if (traceEnabled) {
logger.trace("Ignored because not readable: " + resource);
}
}
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
}
// 3. 返回所有扫描出来的候选 components
return candidates;
}
- (续)
- 扫描出来的 resources 属性如下
- (续)
- 最后的候选 components 属性(只有 com.lagou.config.MyDataSourceConfig 与 com.lagou.controller.TestController )如下
- 其中,registerBeanDefinition() 会调用 BeanDefinitionReaderUtils 来注册扫描出来的类
java
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public class ClassPathBeanDefinitionScanner extends ClassPathScanningCandidateComponentProvider {
...
protected void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) {
// 1. 注册扫描出来的类。这里先注册 com.lagou.config.MyDataSourceConfig,后注册 com.lagou.controller.TestController
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, registry);
}
}
- (续)
- BeanDefinitionReaderUtils 又会通过 BeanDefinitionRegistry (其实就是我们一开始创建的上下文转换强转过来的)调用 registerBeanDefinition() 方法进行注册
java
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public abstract class BeanDefinitionReaderUtils {
...
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
// 1. 通过 BeanDefinitionRegistry 注册扫描出来的类,这里是先注册 com.lagou.config.MyDataSourceConfig,后注册 com.lagou.controller.TestController
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// Register aliases for bean name, if any.
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
}
- (续)
- 最后会把这些扫描出来的类,放到 beanDefinitionMap 属性中
java
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public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
/** List of bean definition names, in registration order. */
private volatile List<String> beanDefinitionNames = new ArrayList<>(256);
/** Map of bean definition objects, keyed by bean name. */
private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);
...
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
Assert.hasText(beanName, "Bean name must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
if (beanDefinition instanceof AbstractBeanDefinition) {
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
}
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (logger.isInfoEnabled()) {
logger.info("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
existingDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(existingDefinition)) {
if (logger.isDebugEnabled()) {
logger.debug("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (logger.isTraceEnabled()) {
logger.trace("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
// 1. 把对应的 beanDefinition 注册到 beanDefinitionMap 中
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
removeManualSingletonName(beanName);
}
}
else {
// Still in startup registration phase
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
removeManualSingletonName(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
else if (isConfigurationFrozen()) {
clearByTypeCache();
}
}
}
- 返回完 ComponentScans 注解扫描的类之后,会判断候选类是不是有 @Configuration 标记,有的话,会继续深度调用 processConfigurationClass() ,继续扫描所有候选类,注册进 beanDefinitionMap 中
java
复制代码
class ConfigurationClassParser {
private final ComponentScanAnnotationParser componentScanParser;
private final ConditionEvaluator conditionEvaluator;
private final Environment environment;
...
@Nullable
protected final SourceClass doProcessConfigurationClass(
ConfigurationClass configClass, SourceClass sourceClass, Predicate<String> filter)
throws IOException {
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
// 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");
}
}
// 扫描处理所有 @ComponentScan 注解
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) {
// 解析 @ComponentScan 的注解,然后把相关对象
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();
}
// 1. 判断扫描的类是不是用 @Configuration 标记
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
// 2. 是的话继续解析该配置类
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
...
}
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);
// 3. 形成递归调用解析
processConfigurationClass(new ConfigurationClass(reader, beanName), DEFAULT_EXCLUSION_FILTER);
}
}
- 直到这里我们就能够明白如何把主类所在的类路径下相关的类通过 @ComponentScan 注册到 IOC 容器中,像相关的 @Import 、@ImportResource 注册,也是在 processConfigurationClass() 这个方法里解析,下节再解析
- 总结