Spring IOC源码解析 xml篇
Spring中使用ClassPathXmlApplicationContext加载XML文件
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring.xml");
Juggler juggler = (Juggler) context.getBean("duke");
juggler.perform();
}
- ClassPathXmlApplicationContext ：从程序内加载配置文件
- FileSystemXmlApplicationContext ：从文件系统中加载配置文件
- AnnotationConfigApplicationContext ：处理注解式编程
一、ClassPathXmlApplicationContext概览
public class ClassPathXmlApplicationContext extends AbstractXmlApplicationContext {
//配置文件数组
private Resource[] configResources;
// 指定ApplicationContext的父容器
public ClassPathXmlApplicationContext(ApplicationContext parent) {
super(parent);
}
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {
super(parent);
// 根据提供的路径，处理成配置文件数组(以分号、逗号、空格、tab、换行符分割)
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
}
核心部分分别为setConfigLocations() 和 refresh()
往下走
public void setConfigLocations(String... locations) {
if (locations != null) {
Assert.noNullElements(locations, "Config locations must not be null");
this.configLocations = new String[locations.length];
for (int i = 0; i < locations.length; i++) {
//往下走
this.configLocations[i] = resolvePath(locations[i]).trim();
}
}
else {
this.configLocations = null;
}
}
protected String resolvePath(String path) {
return getEnvironment().resolveRequiredPlaceholders(path);
}
getEnvironment()获取环境变量
public ConfigurableEnvironment getEnvironment() {
if (this.environment == null) {
this.environment = createEnvironment();
}
return this.environment;
}
protected ConfigurableEnvironment createEnvironment() {
return new StandardEnvironment();
}
StandardEnvironment层次结构
初始化主要执行一下函数
protected void customizePropertySources(MutablePropertySources propertySources) {
propertySources.addLast(new MapPropertySource(SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME, getSystemProperties()));
propertySources.addLast(new SystemEnvironmentPropertySource(SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, getSystemEnvironment()));
}
getSystemProperties()获取系统属性
getSystemEnvironment() 获取系统环境变量
回到resolveRequiredPlaceholders
public String resolveRequiredPlaceholders(String text) throws IllegalArgumentException {
if (this.strictHelper == null) {
this.strictHelper = createPlaceholderHelper(false);
}
return doResolvePlaceholders(text, this.strictHelper);
}
private String doResolvePlaceholders(String text, PropertyPlaceholderHelper helper) {
return helper.replacePlaceholders(text, new PropertyPlaceholderHelper.PlaceholderResolver() {
@Override
public String resolvePlaceholder(String placeholderName) {
return getPropertyAsRawString(placeholderName);
}
});
}
public String replacePlaceholders(String value, PlaceholderResolver placeholderResolver) {
Assert.notNull(value, "'value' must not be null");
return parseStringValue(value, placeholderResolver, new HashSet());
}
protected String parseStringValue(
String value, PlaceholderResolver placeholderResolver, Set visitedPlaceholders) {
StringBuilder result = new StringBuilder(value);
int startIndex = value.indexOf(this.placeholderPrefix);
while (startIndex != -1) {
int endIndex = findPlaceholderEndIndex(result, startIndex);
if (endIndex != -1) {
String placeholder = result.substring(startIndex + this.placeholderPrefix.length(), endIndex);
String originalPlaceholder = placeholder;
if (!visitedPlaceholders.add(originalPlaceholder)) {
throw new IllegalArgumentException(
"Circular placeholder reference '" + originalPlaceholder + "' in property definitions");
}
// Recursive invocation, parsing placeholders contained in the placeholder key.
placeholder = parseStringValue(placeholder, placeholderResolver, visitedPlaceholders);
// Now obtain the value for the fully resolved key...
String propVal = placeholderResolver.resolvePlaceholder(placeholder);
if (propVal == null && this.valueSeparator != null) {
int separatorIndex = placeholder.indexOf(this.valueSeparator);
if (separatorIndex != -1) {
String actualPlaceholder = placeholder.substring(0, separatorIndex);
String defaultValue = placeholder.substring(separatorIndex + this.valueSeparator.length());
propVal = placeholderResolver.resolvePlaceholder(actualPlaceholder);
if (propVal == null) {
propVal = defaultValue;
}
}
}
if (propVal != null) {
// Recursive invocation, parsing placeholders contained in the
// previously resolved placeholder value.
propVal = parseStringValue(propVal, placeholderResolver, visitedPlaceholders);
result.replace(startIndex, endIndex + this.placeholderSuffix.length(), propVal);
if (logger.isTraceEnabled()) {
logger.trace("Resolved placeholder '" + placeholder + "'");
}
startIndex = result.indexOf(this.placeholderPrefix, startIndex + propVal.length());
}
else if (this.ignoreUnresolvablePlaceholders) {
// Proceed with unprocessed value.
startIndex = result.indexOf(this.placeholderPrefix, endIndex + this.placeholderSuffix.length());
}
else {
throw new IllegalArgumentException("Could not resolve placeholder '" +
placeholder + "'" + " in value \"" + value + "\"");
}
visitedPlaceholders.remove(originalPlaceholder);
}
else {
startIndex = -1;
}
}
return result.toString();
}
parseStringValue 这个方法主要就是处理所有使用${}方式的占位符
重头戏：refresh
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// 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();
}
}
}
-
synchronized
为了避免refresh()还没有结束，再次发起启动或者销毁容器引起的冲突 -
prepareRefresh()
做一些准备工作，记录容器的启动时间、标记“已启动”状态、检查环境变量等protected void prepareRefresh() { this.startupDate = System.currentTimeMillis(); this.closed.set(false); this.active.set(true); if (logger.isInfoEnabled()) { logger.info("Refreshing " + this); } // 初始化加载配置文件方法，没有具体实现，一个留给用户的扩展点 initPropertySources(); //检查所需的环境变量 getEnvironment().validateRequiredProperties(); this.earlyApplicationEvents = new LinkedHashSet(); } //主要作用：如果存在环境变量的value为空的时候就抛异常，然后停止启动Spring public void validateRequiredProperties() { MissingRequiredPropertiesException ex = new MissingRequiredPropertiesException(); for (String key : this.requiredProperties) { if (this.getProperty(key) == null) { ex.addMissingRequiredProperty(key); } } if (!ex.getMissingRequiredProperties().isEmpty()) { throw ex; } } -
obtainFreshBeanFactory()
负责BeanFactory初始化，Bean的加载、注册等事件
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
protected final void refreshBeanFactory() throws BeansException {
// 如果存在BeanFactory，销毁BeanFactory
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
//创建新的BeanFactory
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
// 加载 Bean 到 BeanFactory 中
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {
//设置是否允许Bean覆盖
if (this.allowBeanDefinitionOverriding != null) {
beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
//设置是否允许循环引用
if (this.allowCircularReferences != null) {
beanFactory.setAllowCircularReferences(this.allowCircularReferences);
}
}
BeanFactory是Bean的一个容器。BeanDefinition是Bean的一个形式（它里面包含了Bean指向的类、是否单例、是否懒加载、Bean的依赖关系等相关的属性）。BeanFactory中就是保存的BeanDefinition。
查看BeanDefinition接口
public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {
//Bean的生命周期：singleton、prototype
String SCOPE_SINGLETON = ConfigurableBeanFactory.SCOPE_SINGLETON;
String SCOPE_PROTOTYPE = ConfigurableBeanFactory.SCOPE_PROTOTYPE;
//设置父Bean
void setParentName(String parentName);
//获取父Bean
String getParentName();
//设置Bean的类名称
void setBeanClassName(String beanClassName);
//获取Bean的类名称
String getBeanClassName();
//设置Bean的scope
void setScope(String scope);
//获取Bean的scope
String getScope();
//设置是否允许懒加载
void setLazyInit(boolean lazyInit);
boolean isLazyInit();
//设置该Bean依赖的所有Bean
void setDependsOn(String... dependsOn);
//返回该Bean的所有依赖
String[] getDependsOn();
// 设置该Bean是否可以注入到其他Bean中
void setAutowireCandidate(boolean autowireCandidate);
boolean isAutowireCandidate();
// 同一接口的多个实现，如果不指定名字的话，Spring会优先选择设置primary为true的bean
void setPrimary(boolean primary);
boolean isPrimary();
// 指定工厂名称
void setFactoryBeanName(String factoryBeanName);
String getFactoryBeanName();
// 指定工厂类中的工厂方法名称
void setFactoryMethodName(String factoryMethodName);
String getFactoryMethodName();
// 构造器参数
ConstructorArgumentValues getConstructorArgumentValues();
// Bean 中的属性值，后面给 bean 注入属性值的时候会说到
MutablePropertyValues getPropertyValues();
boolean isSingleton();
boolean isPrototype();
// 如果这个 Bean 是被设置为 abstract，那么不能实例化，常用于作为 父bean 用于继承
boolean isAbstract();
int getRole();
String getDescription();
String getResourceDescription();
BeanDefinition getOriginatingBeanDefinition();
}
Bean的作用域
loadBeanDefinitions：读取配置文件
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// 实例化XmlBeanDefinitionReader
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
// 初始化 BeanDefinitionReader
initBeanDefinitionReader(beanDefinitionReader);
// 接着往下看
loadBeanDefinitions(beanDefinitionReader);
}
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
String[] configLocations = getConfigLocations();
if (configLocations != null) {
reader.loadBeanDefinitions(configLocations);
}
}
第一个if是看有没有系统指定的配置文件，如果没有的话就走第二个if加载我们最开始传入的classpath:application-ioc.xml
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
Assert.notNull(resources, "Resource array must not be null");
int counter = 0;
// 循环，处理所有配置文件，咱们这里就传了一个
for (Resource resource : resources) {
// 继续往下看
counter += loadBeanDefinitions(resource);
}
// 最后返回加载的所有BeanDefinition的数量
return counter;
}
@Override
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
return loadBeanDefinitions(location, null);
}
public int loadBeanDefinitions(String location, @Nullable Set actualResources) throws BeanDefinitionStoreException {
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
}
if (resourceLoader instanceof ResourcePatternResolver) {
try {
//将配置文件转换为Resource对象
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
//接着往下看
int loadCount = loadBeanDefinitions(resources);
if (actualResources != null) {
for (Resource resource : resources) {
actualResources.add(resource);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
}
return loadCount;
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"Could not resolve bean definition resource pattern [" + location + "]", ex);
}
}
else {
// Can only load single resources by absolute URL.
Resource resource = resourceLoader.getResource(location);
int loadCount = loadBeanDefinitions(resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
}
return loadCount;
}
}
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isInfoEnabled()) {
logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}
Set currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
//获取文件流
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
//加载
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
finally {
inputStream.close();
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"IOException parsing XML document from " + encodedResource.getResource(), ex);
}
finally {
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
//第一步：将 xml 文件转换为 Document 对象
Document doc = doLoadDocument(inputSource, resource);
//第二步：根据Document对象注册Bean
return registerBeanDefinitions(doc, resource);
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (SAXParseException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
}
catch (SAXException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"XML document from " + resource + " is invalid", ex);
}
catch (ParserConfigurationException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Parser configuration exception parsing XML from " + resource, ex);
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"IOException parsing XML document from " + resource, ex);
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Unexpected exception parsing XML document from " + resource, ex);
}
}
将XML文件转换为Document对象：
protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
getValidationModeForResource(resource), isNamespaceAware());
}
public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {
DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
if (logger.isDebugEnabled()) {
logger.debug("Using JAXP provider [" + factory.getClass().getName() + "]");
}
DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
return builder.parse(inputSource);
}
注册Bean
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
//构建读取Document的工具类
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
//获取已注册的bean数量
int countBefore = getRegistry().getBeanDefinitionCount();
// 在这接着往下看
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
//总注册的bean减去之前注册的bean就是本次注册的bean
return getRegistry().getBeanDefinitionCount() - countBefore;
}
@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
//获取Document的根节点
Element root = doc.getDocumentElement();
//继续往下
doRegisterBeanDefinitions(root);
}
protected void doRegisterBeanDefinitions(Element root) {
// 当前根节点
BeanDefinitionParserDelegate parent = this.delegate;
this.delegate = createDelegate(getReaderContext(), root, parent);
if (this.delegate.isDefaultNamespace(root)) {
// 获取 protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
if (delegate.isDefaultNamespace(root)) {
NodeList nl = root.getChildNodes();
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node instanceof Element) {
Element ele = (Element) node;
if (delegate.isDefaultNamespace(ele)) {
parseDefaultElement(ele, delegate);
}
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//创建BeanDefinition
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to register bean definition with name '" +
bdHolder.getBeanName() + "'", ele, ex);
}
// Send registration event.
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
return parseBeanDefinitionElement(ele, null);
}
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
String id = ele.getAttribute(ID_ATTRIBUTE);
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
List aliases = new ArrayList();
// 将 name 属性的定义按照 “逗号、分号、空格” 切分，形成一个 别名列表数组，
if (StringUtils.hasLength(nameAttr)) {
String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);
aliases.addAll(Arrays.asList(nameArr));
}
String beanName = id;
// 如果没有指定id, 那么用别名列表的第一个名字作为beanName
if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
beanName = aliases.remove(0);
if (logger.isDebugEnabled()) {
logger.debug("No XML 'id' specified - using '" + beanName +
"' as bean name and " + aliases + " as aliases");
}
}
if (containingBean == null) {
checkNameUniqueness(beanName, aliases, ele);
}
// 根据 ... 中的配置创建 BeanDefinition，然后把配置中的信息都设置到实例中,
// 这行执行完毕，一个 BeanDefinition 实例就出来了。等下接着往下看
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
// 创建BeanDefinition
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, BeanDefinition containingBean) {
this.parseState.push(new BeanEntry(beanName));
String className = null;
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
try {
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
// 创建 BeanDefinition，然后设置类信息
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
// 设置 BeanDefinition 的一堆属性，这些属性定义在 AbstractBeanDefinition 中
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
/**
* 下面的一堆是解析 ...... 内部的子元素，
* 解析出来以后的信息都放到 bd 的属性中
*/
// 解析
parseMetaElements(ele, bd);
// 解析 注册Bean
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
String beanName = definitionHolder.getBeanName();
// 注册这个 Bean
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// 如果配置有别名的话，也要根据别名全部注册一遍
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
@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 oldBeanDefinition;
// 所有的 Bean 注册后都会被放入到这个beanDefinitionMap 中，查看是否已存在这个bean
oldBeanDefinition = this.beanDefinitionMap.get(beanName);
// 处理重复名称的 Bean 定义的情况
if (oldBeanDefinition != null) {
if (!isAllowBeanDefinitionOverriding()) {
// 如果不允许覆盖的话，抛异常
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
"': There is already [" + oldBeanDefinition + "] bound.");
}
else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) {
// 用框架定义的 Bean 覆盖用户自定义的 Bean
if (this.logger.isWarnEnabled()) {
this.logger.warn("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
oldBeanDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(oldBeanDefinition)) {
// 用新的 Bean 覆盖旧的 Bean
if (this.logger.isWarnEnabled()) {
this.logger.warn("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
oldBeanDefinition + "] with [" + beanDefinition + "]");
}
}
else {
// log...用同等的 Bean 覆盖旧的 Bean
if (this.logger.isInfoEnabled()) {
this.logger.info("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + oldBeanDefinition +
"] with [" + beanDefinition + "]");
}
}
// 覆盖
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
// 判断是否已经有其他的 Bean 开始初始化了.注意，"注册Bean" 这个动作结束，Bean 依然还没有初始化 在 Spring 容器启动的最后，会 预初始化 所有的 singleton beans
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List updatedDefinitions = new ArrayList(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set updatedSingletons = new LinkedHashSet(this.manualSingletonNames);
updatedSingletons.remove(beanName);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// 将 BeanDefinition 放到这个 map 中，这个 map 保存了所有的 BeanDefinition
this.beanDefinitionMap.put(beanName, beanDefinition);
// 这是个 ArrayList，所以会按照 bean 配置的顺序保存每一个注册的 Bean 的名字
this.beanDefinitionNames.add(beanName);
// 这是个 LinkedHashSet，代表的是手动注册的 singleton bean，
this.manualSingletonNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (oldBeanDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}
- prepareBeanFactory
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// 设置为加载当前ApplicationContext类的类加载器
beanFactory.setBeanClassLoader(getClassLoader());
// 设置 BeanExpressionResolver
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// 这里是Spring的又一个扩展点
//在所有实现了Aware接口的bean在初始化的时候，这个 processor负责回调，
// 这个我们很常用，如我们会为了获取 ApplicationContext 而 implement ApplicationContextAware
// 注意：它不仅仅回调 ApplicationContextAware，还会负责回调 EnvironmentAware、ResourceLoaderAware 等
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
// 下面几行的意思就是，如果某个 bean 依赖于以下几个接口的实现类，在自动装配的时候忽略它们，Spring 会通过其他方式来处理这些依赖。
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
//下面几行就是为特殊的几个 bean 赋值，如果有 bean 依赖了以下几个，会注入这边相应的值
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// 注册 事件监听器
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// 如果存在bean名称为loadTimeWeaver的bean则注册一个BeanPostProcessor
if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// 如果没有定义 "environment" 这个 bean，那么 Spring 会 "手动" 注册一个
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
// 如果没有定义 "systemProperties" 这个 bean，那么 Spring 会 "手动" 注册一个
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
// 如果没有定义 "systemEnvironment" 这个 bean，那么 Spring 会 "手动" 注册一个
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}
- postProcessBeanFactory()
这个比较简单，又是Spring的一个扩展点
如果有Bean实现了BeanFactoryPostProcessor接口，
那么在容器初始化以后，Spring 会负责调用里面的 postProcessBeanFactory 方法。具体的子类可以在这步的时候添加一些特殊的 BeanFactoryPostProcessor 的实现类或做点什么事
-
invokeBeanFactoryPostProcessors()
调用BeanFactoryPostProcessor各个实现类的postProcessBeanFactory(factory) 方法 -
registerBeanPostProcessors()
又是一个扩展点
注册 BeanPostProcessor 的实现类，注意不是BeanFactoryPostProcessor
此接口有两个方法: postProcessBeforeInitialization 和 postProcessAfterInitialization分别会在Bean初始化之前和初始化之后得到执行
initMessageSource()
初始化当前 ApplicationContext 的 MessageSource，有想了解国际化的相关知识可以深入研究一下
9. initApplicationEventMulticaster()
这个方法主要为初始化当前 ApplicationContext 的事件广播器
private void initApplicationEventMulticaster() throws BeansException {
//如果用户配置了自定义事件广播器，就使用用户的
if (containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME )) {
this.applicationEventMulticaster = (ApplicationEventMulticaster)
getBean( APPLICATION_EVENT_MULTICASTER_BEAN_NAME ,
ApplicationEventMulticaster.class );
if (logger.isInfoEnabled()) {
logger.info("Using ApplicationEventMulticaster ["
+ this. applicationEventMulticaster + "]" );
}
}else {
//使用默认的时间广播器
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster();
if (logger.isInfoEnabled()) {
logger.info("Unable to locate ApplicationEventMulticaster with name '"+
APPLICATION_EVENT_MULTICASTER_BEAN_NAME +
"': using default [" + this .applicationEventMulticaster + "]");
}
}
}
onRefresh()
又是一个扩展点，子类可以在这里来搞事情registerListeners()
注册事件监听器
protected void registerListeners() {
//先添加手动set的一些监听器
for (ApplicationListener listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
//取到监听器的名称，设置到广播器
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
// 如果存在早期应用事件，发布
Set earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}