refresh方法
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
// 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);
StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
beanPostProcess.end();
// 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();
contextRefresh.end();
}
}
}
OK 一行一行代码的看
第一行
synchronized (this.startupShutdownMonitor) {
这一行很明显了，给startupShutdownMonitor这个成员变量加锁，这个成员变量是什么呢？
锁住一个对象，防止多线程同时执行初始化的操作
第二行
StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
创建一个静态内部类对象DefaultStartupStep
第三行
prepareRefresh();
在刷新之前设置一些参数，比如设置开始时间戳，上下文是否激活的标志，输出刷新上下文的信息，验证一些必要的属性。
protected void prepareRefresh() {
// Switch to active.
this.startupDate = System.currentTimeMillis();
this.closed.set(false);
this.active.set(true);
if (logger.isDebugEnabled()) {
if (logger.isTraceEnabled()) {
logger.trace("Refreshing " + this);
}
else {
logger.debug("Refreshing " + getDisplayName());
}
}
// Initialize any placeholder property sources in the context environment.
initPropertySources();
// Validate that all properties marked as required are resolvable:
// see ConfigurablePropertyResolver#setRequiredProperties
getEnvironment().validateRequiredProperties();
// Store pre-refresh ApplicationListeners...
if (this.earlyApplicationListeners == null) {
this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
}
else {
// Reset local application listeners to pre-refresh state.
this.applicationListeners.clear();
this.applicationListeners.addAll(this.earlyApplicationListeners);
}
// Allow for the collection of early ApplicationEvents,
// to be published once the multicaster is available...
this.earlyApplicationEvents = new LinkedHashSet<>();
}
设置开始时间，计时用。设置标记，输出日志，初始化监听器，检查环境变量，创建事件LinkedHashSet等。
其中检查环境变量的核心方法为
getEnvironment().validateRequiredProperties()，简单来说就是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
第四行
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
点进去看
我们再来看refreshBeanFactory方法
正是在这个方法中销毁了应用上下文的原有BeanFactory并新建了DefaultListableBeanFactory，这个哥们的背景相当大，所有关于容器的接口、抽象类他都继承了。
看一下customizeBeanFactory方法
通过名字我们可以看得出来，就是用来设置 BeanFactory 的两个配置属性：是否允许 Bean 覆盖、是否允许循环引用。
接下来就是一个超级重要的方法loadBeanDefinitions
在看这个方法之前，我们必须了解一个东西，那就是：BeanDefinition。
我们知道BeanFactory是一个Bean容器，而BeanDefinition就是Bean的一
种形式（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。
看一下BeanDefinition接口
public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {
// Bean的生命周期，默认只提供sington和prototype两种，
//在WebApplicationContext中还会有request, session,
//globalSession, application, websocket 等
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);
String getScope();
// 设置是否懒加载
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);
// 该Bean是否可以注入到其他Bean中
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);
// 是否是primary的
boolean isPrimary();
// 指定工厂名称
void setFactoryBeanName(String factoryBeanName); // 获取工厂名称 String getFactoryBeanName(); // 指定工厂类中的工厂方法名称 void setFactoryMethodName(String factoryMethodName); // 获取工厂类中的工厂方法名称 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();
// 是否 singleton
boolean isSingleton();
// 是否 prototype
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();
}
接下来继续看loadBeanDefinitions方法
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
// Allow a subclass to provide custom initialization of the reader,
// then proceed with actually loading the bean definitions.
initBeanDefinitionReader(beanDefinitionReader);
loadBeanDefinitions(beanDefinitionReader);
}
这里首先实例化XmlBeanDefinitionReader，因为这里使用的是xml文件的形式，所以使用XmlBeanDefinitionReader来加载。它还有三个兄弟。
此对象中包含了对xml的验证，对各种标签的解析等。
之后此方法对属性进行了填充。后执行了初始化，主要工作如下
继续看loadBeanDefinitions(beanDefinitionReader)方法
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进入loadBeanDefinitions中
public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {
ResourceLoader resourceLoader = this.getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException("Cannot load bean definitions from location [" + location + "]: no ResourceLoader available");
} else {
int count;
if (resourceLoader instanceof ResourcePatternResolver) {
try {
Resource[] resources = ((ResourcePatternResolver)resourceLoader).getResources(location);
count = this.loadBeanDefinitions(resources);
if (actualResources != null) {
Collections.addAll(actualResources, resources);
}
if (this.logger.isTraceEnabled()) {
this.logger.trace("Loaded " + count + " bean definitions from location pattern [" + location + "]");
}
return count;
} catch (IOException var6) {
throw new BeanDefinitionStoreException("Could not resolve bean definition resource pattern [" + location + "]", var6);
}
} else {
Resource resource = resourceLoader.getResource(location);
count = this.loadBeanDefinitions((Resource)resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (this.logger.isTraceEnabled()) {
this.logger.trace("Loaded " + count + " bean definitions from location [" + location + "]");
}
return count;
}
}
}
具体细节就不解释了，进入到下图的方法中
我们会来到XmlBeanDefinitionReader的loadBeanDefinitions方法。
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (this.logger.isTraceEnabled()) {
this.logger.trace("Loading XML bean definitions from " + encodedResource);
}
Set<EncodedResource> currentResources = (Set)this.resourcesCurrentlyBeingLoaded.get();
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!");
} else {
int var6;
try {
InputStream inputStream = encodedResource.getResource().getInputStream();
Throwable var4 = null;
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
var6 = this.doLoadBeanDefinitions(inputSource, encodedResource.getResource());
} catch (Throwable var24) {
var4 = var24;
throw var24;
} finally {
if (inputStream != null) {
if (var4 != null) {
try {
inputStream.close();
} catch (Throwable var23) {
var4.addSuppressed(var23);
}
} else {
inputStream.close();
}
}
}
} catch (IOException var26) {
throw new BeanDefinitionStoreException("IOException parsing XML document from " + encodedResource.getResource(), var26);
} finally {
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
return var6;
}
}
此方法中包含doLoadBeanDefinitions方法
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource) throws BeanDefinitionStoreException {
try {
Document doc = this.doLoadDocument(inputSource, resource);
int count = this.registerBeanDefinitions(doc, resource);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Loaded " + count + " bean definitions from " + resource);
}
return count;
} catch (BeanDefinitionStoreException var5) {
throw var5;
} catch (SAXParseException var6) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(), "Line " + var6.getLineNumber() + " in XML document from " + resource + " is invalid", var6);
} catch (SAXException var7) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(), "XML document from " + resource + " is invalid", var7);
} catch (ParserConfigurationException var8) {
throw new BeanDefinitionStoreException(resource.getDescription(), "Parser configuration exception parsing XML from " + resource, var8);
} catch (IOException var9) {
throw new BeanDefinitionStoreException(resource.getDescription(), "IOException parsing XML document from " + resource, var9);
} catch (Throwable var10) {
throw new BeanDefinitionStoreException(resource.getDescription(), "Unexpected exception parsing XML document from " + resource, var10);
}
}
这个方法十分重要，这个方法将xml文件转成Document文件，并注册bean。接下来看这个关键的解析方法registerBeanDefinitions。
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;}
registerBeanDefinitions->doRegisterBeanDefinitions
protected void doRegisterBeanDefinitions(Element root) {
BeanDefinitionParserDelegate parent = this.delegate;
this.delegate = this.createDelegate(this.getReaderContext(), root, parent);
if (this.delegate.isDefaultNamespace(root)) {
String profileSpec = root.getAttribute("profile");
if (StringUtils.hasText(profileSpec)) {
String[] specifiedProfiles = StringUtils.tokenizeToStringArray(profileSpec, ",; ");
if (!this.getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Skipped XML bean definition file due to specified profiles [" + profileSpec + "] not matching: " + this.getReaderContext().getResource());
}
return;
}
}
}
this.preProcessXml(root);
this.parseBeanDefinitions(root, this.delegate);
this.postProcessXml(root);
this.delegate = parent;
}
接下来看parseBeanDefinitions()
看parseDefaultElement()方法
解析import、alias、bean、beans
看解析Bean中processBeanDefinition方法
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, this.getReaderContext().getRegistry());
} catch (BeanDefinitionStoreException var5) {
this.getReaderContext().error("Failed to register bean definition with name '" + bdHolder.getBeanName() + "'", ele, var5);
}
this.getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}
这个方法最主要的事情就是创建了BeanDefinition。 看parseBeanDefinitionElement
@Nullable
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) {
String id = ele.getAttribute("id");
String nameAttr = ele.getAttribute("name");
List<String> aliases = new ArrayList();
if (StringUtils.hasLength(nameAttr)) {
String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, ",; ");
aliases.addAll(Arrays.asList(nameArr));
}
String beanName = id;
if (!StringUtils.hasText(id) && !aliases.isEmpty()) {
beanName = (String)aliases.remove(0);
if (this.logger.isTraceEnabled()) {
this.logger.trace("No XML 'id' specified - using '" + beanName + "' as bean name and " + aliases + " as aliases");
}
}
if (containingBean == null) {
this.checkNameUniqueness(beanName, aliases, ele);
}
AbstractBeanDefinition beanDefinition = this.parseBeanDefinitionElement(ele, beanName, containingBean);
if (beanDefinition != null) {
if (!StringUtils.hasText(beanName)) {
try {
if (containingBean != null) {
beanName = BeanDefinitionReaderUtils.generateBeanName(beanDefinition, this.readerContext.getRegistry(), true);
} else {
beanName = this.readerContext.generateBeanName(beanDefinition);
String beanClassName = beanDefinition.getBeanClassName();
if (beanClassName != null && beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() && !this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {
aliases.add(beanClassName);
}
}
if (this.logger.isTraceEnabled()) {
this.logger.trace("Neither XML 'id' nor 'name' specified - using generated bean name [" + beanName + "]");
}
} catch (Exception var9) {
this.error(var9.getMessage(), ele);
return null;
}
}
String[] aliasesArray = StringUtils.toStringArray(aliases);
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
} else {
return null;
}
}
主要看这么几行
parseBeanDefinitionElement方法
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 <bean>......</bean>
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 <meta />
parseMetaElements(ele, bd);
// 解析 <lookup-method />
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
// 解析 <replaced-method />
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
// 解析 <constructor-arg />
parseConstructorArgElements(ele, bd);
// 解析 <property />
parsePropertyElements(ele, bd);
// 解析 <qualifier />
parseQualifierElements(ele, bd);
bd.setResource(this.readerContext.getResource());
bd.setSource(extractSource(ele));
return bd;
}
catch (ClassNotFoundException ex) {
error("Bean class [" + className + "] not found", ele, ex);
}
catch (NoClassDefFoundError err) {
error("Class that bean class [" + className + "] depends on not found", ele, err); }
catch (Throwable ex) {
error("Unexpected failure during bean definition parsing", ele, ex);
}
finally {
this.parseState.pop();
}
return null;
}
至此BeanDefinition创建完毕。
下面查看注册registerBeanDefinition
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 var8) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", var8);
}
}
BeanDefinition existingDefinition = (BeanDefinition)this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
if (!this.isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
}
if (existingDefinition.getRole() < beanDefinition.getRole()) {
if (this.logger.isInfoEnabled()) {
this.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 (this.logger.isDebugEnabled()) {
this.logger.debug("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]");
}
} else if (this.logger.isTraceEnabled()) {
this.logger.trace("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]");
}
this.beanDefinitionMap.put(beanName, beanDefinition);
} else {
if (this.hasBeanCreationStarted()) {
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;
this.removeManualSingletonName(beanName);
}
} else {
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
this.removeManualSingletonName(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition == null && !this.containsSingleton(beanName)) {
if (this.isConfigurationFrozen()) {
this.clearByTypeCache();
}
} else {
this.resetBeanDefinition(beanName);
}
}
这个方法看不下去...
不愧是高富帅DefaultListableBeanFactory，成员变量如下。
// JSR-330 支持
private static Class<?> javaxInjectProviderClass;
// DefaultListableBeanFactory引用的缓存
private static final Map<String, Reference<DefaultListableBeanFactory>> serializableFactories = new ConcurrentHashMap<>(8);
// 序列号id
private String serializationId;
// 是否允许用相同的名称重新注册不同的定义
private boolean allowBeanDefinitionOverriding = true;
// 是否允许懒加载
private boolean allowEagerClassLoading = true;
// 依赖排序顺序
private Comparator<Object> dependencyComparator;
// 解析器，用于检查bean定义是否为自动装配候选
private AutowireCandidateResolver autowireCandidateResolver = new SimpleAutowireCandidateResolver();
// 依赖类型和自动注入值的映射
private final Map<Class<?>, Object> resolvableDependencies = new ConcurrentHashMap<>(16);
// BeanDefinition和beanName的映射
private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);
// 依赖类型和单例、非单例bean的映射
private final Map<Class<?>, String[]> allBeanNamesByType = new ConcurrentHashMap<>(64);
// 依赖类型和单例bean的映射
private final Map<Class<?>, String[]> singletonBeanNamesByType = new ConcurrentHashMap<>(64);
// bean定义名称列表，按注册顺序排列。
private volatile List<String> beanDefinitionNames = new ArrayList<>(256);
// 手动注册的单例，按注册顺序排列
private volatile Set<String> manualSingletonNames = new LinkedHashSet<>(16);
// 固定配置的缓存的bean定义名数组
private volatile String[] frozenBeanDefinitionNames;
// 是否可以缓存所有bean的bean定义元数据
private volatile boolean configurationFrozen = false;
到这里已经初始化了 Bean 容器，的配置也相应的转换为了一个个BeanDefinition，然后注册了所有的BeanDefinition到beanDefinitionMap。
看得我眼花缭乱，还好我年轻还顶得住.. 明天继续更!
