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本文源码版本5.1.x.话不多说,开始
首先是配置类
@Configuration
@ComponentScan("com.day01")
public class SpringConfig {
}
IndexService
@Service
public class IndexService {
public IndexService(){
System.out.println("IndexService 构造方法");
}
@PostConstruct
public void init(){
System.out.println("IndexService init方法");
}
public void hello(){
System.out.println("IndexService hello");
}
}
测试类
public static void main(String[] args) {
AnnotationConfigApplicationContext applicationContext=new AnnotationConfigApplicationContext(SpringConfig.class);
//AnnotationConfigApplicationContext applicationContext=new AnnotationConfigApplicationContext(IndexService.class);
IndexService indexService = (IndexService) applicationContext.getBean("indexService");
indexService.hello();
System.out.println(indexService);
}
第一行点进去
public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
//annotatedClasses ---> 配置类的class对象
this();
register(annotatedClasses);
refresh();
}
今天我们先看refresh()方法之前的源码
this()调的构造器如下
public AnnotationConfigApplicationContext() {
/**
* 父类的构造方法
* 创建一个读取注解的Bean定义读取器
* 什么是BeanDefinition
*/
super();
this.reader = new AnnotatedBeanDefinitionReader(this);
//可以用来扫描包或者类，继而转换成BeanDefinition
//但是实际上我们扫描包工作不是scanner这个对象来完成的
//是spring自己new的一个ClassPathBeanDefinitionScanner
//这里的scanner仅仅是为了程序员能够在外部调用AnnotationConfigApplicationContext对象的scan方法
this.scanner = new ClassPathBeanDefinitionScanner(this);
}
/**
* 这个类顾名思义是一个reader，一个读取器
* 读取什么呢？还是顾名思义:AnnotatedBeanDefinition意思是读取一个被加了注解的BeanDefinition
* 这个类在构造方法中实例化的
*/
private final AnnotatedBeanDefinitionReader reader;
/**
* 同意顾名思义，这是一个扫描器，扫描所有加了注解的bean
* 同样是在构造方法中被实例化的
*/
private final ClassPathBeanDefinitionScanner scanner;
先看super()父类构造器
public GenericApplicationContext() {
this.beanFactory = new DefaultListableBeanFactory();
}
可以看出初始化beanFactory 为默认实现DefaultListableBeanFactory
我们看一下些DefaultListableBeanFactory的属性和方法
public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
/** Map of bean definition objects, keyed by bean name. */ private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256); /** List of bean definition names, in registration order. */ private volatile List<String> beanDefinitionNames = new ArrayList<>(256); //手动注册的单例对象的名称列表，按注册顺序排列 /** List of names of manually registered singletons, in registration order. */ private volatile Set<String> manualSingletonNames = new LinkedHashSet<>(16);
@Override
public <T> T getBean(Class<T> requiredType) throws BeansException {
return getBean(requiredType, (Object[]) null);
}
@SuppressWarnings("unchecked")
@Override
public <T> T getBean(Class<T> requiredType, @Nullable Object... args) throws BeansException {
Assert.notNull(requiredType, "Required type must not be null");
Object resolved = resolveBean(ResolvableType.forRawClass(requiredType), args, false);
if (resolved == null) {
throw new NoSuchBeanDefinitionException(requiredType);
}
return (T) resolved;
}
}
可以看出,这是bean工厂的实现类,里面有存BeanDefinition和beanDefinitionNames 的map和getBean等方法
父类构造器结束,就是实例了一个默认的bean工厂,继续下一行
this.reader = new AnnotatedBeanDefinitionReader(this);
点进去看源码
public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry) {
this(registry, getOrCreateEnvironment(registry));
}
这里BeanDefinitionRegistry是一个BeanDefinition注册器
public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
Assert.notNull(environment, "Environment must not be null");
this.registry = registry;
this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
继续看最后一行
public static void registerAnnotationConfigProcessors(BeanDefinitionRegistry registry) {
registerAnnotationConfigProcessors(registry, null);
}
继续跟进去
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
BeanDefinitionRegistry registry, @Nullable Object source) {
DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
if (beanFactory != null) {
if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);//AnnotationAwareOrderComparator主要能解析@Order注解和@Priority
}
if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());//ContextAnnotationAutowireCandidateResolver提供处理延迟加载的功能
}
}
//a Set of BeanDefinitionHolders, containing all bean definitions
//BeanDefinitionHolder是存储BeanDefinitionName和BeanDefinition的一个数据结构
Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<>(8);
//BeanDefinitio的注册，这里很重要，需要理解注册每个bean的类型,CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME=internalConfigurationAnnotationProcessor
if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
//ConfigurationClassPostProcessor是一个BeanFactory的后置处理器，主要功能是解析加了@Configuration的配置类，还会解析@ComponentScan、@ComponentScans注解扫描的包，以及解析@Import等注解
//需要注意的是ConfigurationClassPostProcessor的类型是BeanDefinitionRegistryPostProcessor
//而 BeanDefinitionRegistryPostProcessor 最终实现BeanFactoryPostProcessor这个接口
RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
}
//AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME=internalAutowiredAnnotationProcessor
if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
//AutowiredAnnotationBeanPostProcessor是解析AutoWired注解的BeanPostProcessor
//AutowiredAnnotationBeanPostProcessor 实现了 MergedBeanDefinitionPostProcessor
//MergedBeanDefinitionPostProcessor 最终实现了 BeanPostProcessor
RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
}
//COMMON_ANNOTATION_PROCESSOR_BEAN_NAME=internalCommonAnnotationProcessor
// Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.
if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {
//CommonAnnotationBeanPostProcessor支持对@PostConstruct和@PreDestroy注解,以及对@Resource注解的处理
RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));
}
//PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME=internalPersistenceAnnotationProcessor,跳过,不重要
// Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.
if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition();
try {
def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
AnnotationConfigUtils.class.getClassLoader()));
}
catch (ClassNotFoundException ex) {
throw new IllegalStateException(
"Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);
}
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));
}
//EVENT_LISTENER_PROCESSOR_BEAN_NAME=internalEventListenerProcessor
if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {
//EventListenerMethodProcessor支持事件监听,不太熟
RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));
}
//EVENT_LISTENER_FACTORY_BEAN_NAME=internalEventListenerFactory
if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {
//DefaultEventListenerFactory不太了解,事件监听相关
RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));
}
return beanDefs;
}
这里的BeanDefinitionHolder看下
public class BeanDefinitionHolder implements BeanMetadataElement {
private final BeanDefinition beanDefinition;
private final String beanName;
@Nullable
private final String[] aliases;
//省略
}
可以认为:BeanDefinitionHolder是存储BeanDefinitionName和BeanDefinition的一个数据结构
debug看下最后一行的结果
可以看出,bean工厂已经存在5个BeanDefinition,我们继续看下面的源码
读取器看完了,扫描器先不看了,我们看register(annotatedClasses);方法
public void register(Class<?>... annotatedClasses) {
Assert.notEmpty(annotatedClasses, "At least one annotated class must be specified");
this.reader.register(annotatedClasses);//被注解的类
}
继续跟下去
public void register(Class<?>... annotatedClasses) {
for (Class<?> annotatedClass : annotatedClasses) {
registerBean(annotatedClass);
}
}
这里循环处理所有要处理的annotated类。如:Configuration注解的配置类
public void registerBean(Class<?> annotatedClass) {
doRegisterBean(annotatedClass, null, null, null);
}
继续跟
<T> void doRegisterBean(Class<T> annotatedClass, @Nullable Supplier<T> instanceSupplier, @Nullable String name,
@Nullable Class<? extends Annotation>[] qualifiers, BeanDefinitionCustomizer... definitionCustomizers) {
/**
* 根据指定的bean创建一个AnnotatedGenericBeanDefinition
* 这个AnnotatedGenericBeanDefinition可以理解为一个数据结构
* AnnotatedGenericBeanDefinition包含了类的其他信息,比如一些元信息
* scope，lazy等等.
* 此时因为传入的注解,所以new AnnotatedGenericBeanDefinition
*/
AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(annotatedClass);
/**
* 判断这个类是否需要跳过解析
* 通过代码可以知道spring判断是否跳过解析，主要判断类有没有加注解
*/
if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
return;
}
abd.setInstanceSupplier(instanceSupplier);
/**
* 得到类的作用域 singleton
*/
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
/**
* 把类的作用域添加到数据结构结构中
*/
abd.setScope(scopeMetadata.getScopeName());
/**
* 生成类的名字通过beanNameGenerator
*/
String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));
/**
* 处理类当中的通用注解
* 分析源码可以知道他主要处理
* Lazy DependsOn Primary Role等等注解
* 处理完成之后processCommonDefinitionAnnotations中依然是把他添加到AnnotatedGenericBeanDefinition数据结构当中
*/
AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
if (qualifiers != null) {//qualifiers总是为null
for (Class<? extends Annotation> qualifier : qualifiers) {
//如果配置了@Primary注解，如果加了则作为首选
if (Primary.class == qualifier) {
abd.setPrimary(true);
}
//懒加载注解
else if (Lazy.class == qualifier) {
abd.setLazyInit(true);
}
else {
//如果使用了除@Primary和@Lazy以外的其他注解，则为该Bean添加一个根据名字自动装配的限定符
//这里难以理解，后面会详细介绍
abd.addQualifier(new AutowireCandidateQualifier(qualifier));
}
}
}
//自定义注解
for (BeanDefinitionCustomizer customizer : definitionCustomizers) {
customizer.customize(abd);
}
/**
* 这个BeanDefinitionHolder也是一个数据结构,这个对象放入了BeanDefinition和beanName
*/
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
/**
* ScopedProxyMode 这个知识点比较复杂，需要结合web去理解
* 可以暂时放一下，等说道springmvc的时候再说
* 或者看情况现在说也是一样的
*/
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
/**
* 把上述的这个数据结构注册给registry
* registy就是AnnotatonConfigApplicationContext
* AnnotatonConfigApplicationContext在初始化的時候通過調用父類的構造方法
* 實例化了一个DefaultListableBeanFactory
* *registerBeanDefinition里面就是把definitionHolder这个数据结构包含的信息注册到
* DefaultListableBeanFactory这个工厂
*/
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);//关键代码
}
我们看最后一行关键代码
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();//获取beanName
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());//关键代码
//别名,先不看
// Register aliases for bean name, if any.
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
还是跟关键代码
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
//DefaultListableBeanFactory
this.beanFactory.registerBeanDefinition(beanName, beanDefinition);
}
这里的beanFactory就是前文说的DefaultListableBeanFactory,继续跟
@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) {//验证
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
//这里beanDefinitionMap是存储bean的name和.beanDefinition的map结果,此处有5个spring内置的BeanDefinition
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);//这里的beanName是配置类的名字,existingDefinition应该为null
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 {//进这里
if (hasBeanCreationStarted()) {//这里跳过,不进这里,先不看
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
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 {//关键代码
// Still in startup registration phase
//这里的beanDefinitionMap是一个map,存放beanName,beanDefinition
this.beanDefinitionMap.put(beanName, beanDefinition);
//这里的beanDefinitionNames是一个list,存放beanName
this.beanDefinitionNames.add(beanName);
removeManualSingletonName(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}
这里的关键代码,我标注出来了,就是上面那个bean工厂的默认实现的几个属性
private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);
private volatile List<String> beanDefinitionNames = new ArrayList<>(256);
//手动注册的单例对象的名称列表，按注册顺序排列
/** List of names of manually registered singletons, in registration order. */
private volatile Set<String> manualSingletonNames = new LinkedHashSet<>(16);
到这里register方法就结束了,大概是将我们的类解析成BeanDefinition,并存在bean工厂的beanDefinitionMap 属性中,后面就是refresh()方法了,这个方法太复杂,我们在后面分几个博客来研究他,先看一下源码吧
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
//准备工作包括设置启动时间，是否激活标识位，
// 初始化属性源(property source)配置
// Prepare this context for refreshing.
prepareRefresh();
//此处的beanFactory就是DefaultListableBeanFactory,有Map<String, BeanDefinition> beanDefinitionMap和List<String> beanDefinitionNames等属性
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
//准备工厂
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
//目前是空方法,留给后续扩展
postProcessBeanFactory(beanFactory);
//完成扫描和解析(类--->beanDefinition) beanDefinitionMap
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
//注册beanPostProcessor
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
//初始化应用事件广播器
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
//实例化所有单例的对象
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
好了,这篇文章到这里就结束了.谢谢大家的观看,大家有空的话就帮我点个赞吧
文章中若有错误和疏漏之处,还请各位大佬不吝指出