Spring4源码分析(ClassPathXmlApplicationContext)

Spring4源码分析(ClassPathXmlApplicationContext)

类图


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适当删减了一部分

后边部分构成了BeanFactory的结构体系

BeanFactory提供了获取Bean对象的方法

HierarchicalBeanFactory提供了获取父BeanFactory的方法

ConfigurableBeanFactory提供了设置父BeanFactory的方法

AutowireCapableBeanFactory提供了创建Bean的方法

ListableBeanFactory提供了查找Bean的方法

ConfigurableListableBeanFactory实现了ConfigurableBeanFactory, AutowireCapableBeanFactory, ListableBeanFactory,同事提供了查找BeanDefinition的方法

中间部门实现了左边对应的接口

AbstractBeanFactory

AbstractAutowireCapableBeanFactory

DefaultListableBeanFactory

构成了整个的BeanFactory工厂

提供了BeanFactory的默认实现

左边部分提供了ApplicationContext接口

AbstractApplicationContext

AbstractRefreshableApplicationContext

AbstractRefreshableConfigApplicationContext

AbstractXmlApplicationContext

ClassPathXmlApplicationContext

对BeanFactory做了二次封装

1. 初始化

时序图

1.1 ClassPathXmlApplicationContext:设置了Xml配置文件的位置

public class ClassPathXmlApplicationContext extends AbstractXmlApplicationContext {
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
this(new String[]{configLocation}, true, null);
}

public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {
//调用父类的构造方法,设置父类的ApplicationContext,默认为空
super(parent);
//设置配置文件
setConfigLocations(configLocations);
if (refresh) {
//调用父类的方法,由AbstractApplicationContext实现
refresh();
}
}
}

1.2 AbstractRefreshableConfigApplicationContext提供了设置配置文件的功能

public abstract class AbstractRefreshableConfigApplicationContext extends AbstractRefreshableApplicationContext
implements BeanNameAware, InitializingBean {
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++) {
//设置配置文件的地址
this.configLocations[i] = resolvePath(locations[i]).trim();
}
} else {
this.configLocations = null;
}
}
}

1.3 AbstractApplicationContext提供了刷新容器抽象的方法

public abstract class AbstractApplicationContext extends DefaultResourceLoader
implements ConfigurableApplicationContext, DisposableBean {
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 刷新前执行的方法
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();
}
}
}

protected void prepareRefresh() {
this.startupDate = System.currentTimeMillis();
this.closed.set(false);
this.active.set(true);

if (logger.isInfoEnabled()) {
logger.info("Refreshing " + this);
}

// Initialize any placeholder property sources in the context environment   initPropertySources();
ConfigurablePropertyResolver#setRequiredProperties   getEnvironment().validateRequiredProperties();
this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>();
}

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
}

1.4 AbstractRefreshableApplicationContext实现了抽象方法refreshBeanFactory,并创建了DefaultListableBeanFactory对象

public abstract class AbstractRefreshableApplicationContext extends AbstractApplicationContext {
@Override
protected final void refreshBeanFactory() throws BeansException {
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
//创建DefaultListableBeanFactory
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
//加载BeanDefinition
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 DefaultListableBeanFactory createBeanFactory() {
return new DefaultListableBeanFactory(getInternalParentBeanFactory());
}
}

1.5 AbstractXmlApplicationContext完成了对Xml配置文件的解析,创建了XmlBeanDefinitionReader对象

public abstract class AbstractXmlApplicationContext extends AbstractRefreshableConfigApplicationContext {
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// 创建XmlBeanDefinitionReader
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

initBeanDefinitionReader(beanDefinitionReader);
//加载BeanDefinition
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) {
//通过XmlBeanDefinitionReader加载BeanDefinition
reader.loadBeanDefinitions(configLocations);
}
}
}

1.6 AbstractBeanDefinitionReader抽象了配置文件解析的功能

public abstract class AbstractBeanDefinitionReader implements EnvironmentCapable, BeanDefinitionReader {

@Override
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
Assert.notNull(resources, "Resource array must not be null");
int counter = 0;
for (Resource resource : resources) {
//加载BeanDefinition
counter += loadBeanDefinitions(resource);
}
return counter;
}

@Override
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {
return loadBeanDefinitions(location, null);
}

public int loadBeanDefinitions(String location, Set<Resource> 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) {
// Resource pattern matching available.
try {
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
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 {
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;
}
}

@Override
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {
Assert.notNull(locations, "Location array must not be null");
int counter = 0;
for (String location : locations) {
counter += loadBeanDefinitions(location);
}
return counter;
}
}

1.7 XmlBeanDefinitionReader完成对具体的xml格式配置文件的解析,具体的解析由BeanDefinitionDocumentReader完成

public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader {

@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
return loadBeanDefinitions(new EncodedResource(resource));
}

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<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<EncodedResource>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
//加载BeanDefinition
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 {
//加载XML文档
Document doc = doLoadDocument(inputSource, resource);
//注册BeanDefinition
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);
}
}

protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
getValidationModeForResource(resource), isNamespaceAware());
}

public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
//创建BeanDefinition文档阅读器
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
//注册BeanDefinition
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}

protected BeanDefinitionDocumentReader createBeanDefinitionDocumentReader() {
return BeanDefinitionDocumentReader.class.cast(BeanUtils.instantiateClass(this.documentReaderClass));
}

public XmlReaderContext createReaderContext(Resource resource) {
return new XmlReaderContext(resource, this.problemReporter, this.eventListener,
this.sourceExtractor, this, getNamespaceHandlerResolver());
}
}

1.8 DefaultBeanDefinitionDocumentReader通过BeanDefinitionParserDelegate完成对具体XML的解析

public class DefaultBeanDefinitionDocumentReader implements BeanDefinitionDocumentReader {

@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();
//注册BeanDefinition
doRegisterBeanDefinitions(root);
}

protected final XmlReaderContext getReaderContext() {
return this.readerContext;
}

protected Object extractSource(Element ele) {
return getReaderContext().extractSource(ele);
}

protected void doRegisterBeanDefinitions(Element root) {
BeanDefinitionParserDelegate parent = this.delegate;
//创建BeanDefinition解析器
this.delegate = createDelegate(getReaderContext(), root, parent);
//如果是默认命名空间
if (this.delegate.isDefaultNamespace(root)) {
String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
if (StringUtils.hasText(profileSpec)) {
String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
if (logger.isInfoEnabled()) {
logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec +
"] not matching: " + getReaderContext().getResource());
}
return;
}
}
}

preProcessXml(root);
//解析BeanDefinition
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);

this.delegate = parent;
}

protected BeanDefinitionParserDelegate createDelegate(
XmlReaderContext readerContext, Element root, BeanDefinitionParserDelegate parentDelegate) {

BeanDefinitionParserDelegate delegate = new BeanDefinitionParserDelegate(readerContext);
delegate.initDefaults(root, parentDelegate);
return delegate;
}

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)) {
//默认命名空间
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)) {
//解析BeanDefinition
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
doRegisterBeanDefinitions(ele);
}
}

protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//解析BeanDefinition元素,返回BeanDefinitionHolder对象
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
//注册BeanDefinition
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));
}
}

}

1.9 BeanDefinitionParserDelegate完成对具体的XML的解析,创建了BeanDefinition对象,并注册到了beanFactory工厂

public class BeanDefinitionParserDelegate {

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {
//解析BeanDefinition元素
return parseBeanDefinitionElement(ele, null);
}

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
//获取ID
String id = ele.getAttribute(ID_ATTRIBUTE);
//获取NAME
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);

List<String> aliases = new ArrayList<String>();
if (StringUtils.hasLength(nameAttr)) {
String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);
aliases.addAll(Arrays.asList(nameArr));
}

String beanName = id;
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);
}
//解析BeanDefinition元素,返回BeanDefinition
AbstractBeanDefinition beanDefinition = 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 (logger.isDebugEnabled()) {
logger.debug("Neither XML 'id' nor 'name' specified - " +
"using generated bean name [" + beanName + "]");
}
}
catch (Exception ex) {
error(ex.getMessage(), ele);
return null;
}
}
String[] aliasesArray = StringUtils.toStringArray(aliases);
//返回BeanDefinitionHolder
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
}

return null;
}

public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, BeanDefinition containingBean) {

this.parseState.push(new BeanEntry(beanName));

String className = null;
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
//获取ClassName
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}

try {
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
//创建BeanDefinition
AbstractBeanDefinition bd = createBeanDefinition(className, parent);

parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
//获取description
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));

parseMetaElements(ele, bd);
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());

parseConstructorArgElements(ele, bd);
parsePropertyElements(ele, bd);
parseQualifierElements(ele, bd);
//设置资源文件
bd.setResource(this.readerContext.getResource());
bd.setSource(extractSource(ele));
//返回BeanDefinition
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;
}

protected AbstractBeanDefinition createBeanDefinition(String className, String parentName)
throws ClassNotFoundException {

return BeanDefinitionReaderUtils.createBeanDefinition(
parentName, className, this.readerContext.getBeanClassLoader());
}
}

2 运行

2.1 AbstractApplicationContext提供了getBean方法

public abstract class AbstractApplicationContext extends DefaultResourceLoader
implements ConfigurableApplicationContext, DisposableBean {

@Override
public Object getBean(String name) throws BeansException {
assertBeanFactoryActive();
return getBeanFactory().getBean(name);
}
}

2.2 AbstractRefreshableApplicationContext提供了getBeanFactory方法

public abstract class AbstractRefreshableApplicationContext extends AbstractApplicationContext {

@Override
public final ConfigurableListableBeanFactory getBeanFactory() {
synchronized (this.beanFactoryMonitor) {
if (this.beanFactory == null) {
throw new IllegalStateException("BeanFactory not initialized or already closed - " +
"call 'refresh' before accessing beans via the ApplicationContext");
}
return this.beanFactory;
}
}
}

2.3 AbstractBeanFactory提供了getBean方法获取Bean的实例

public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {
@Override
public Object getBean(String name) throws BeansException {
//获取Bean
return doGetBean(name, null, null, false);
}

public <T> T getBean(String name, Class<T> requiredType, Object... args) throws BeansException {
return doGetBean(name, requiredType, args, false);
}

@SuppressWarnings("unchecked")
protected <T> T doGetBean(
final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
throws BeansException {

final String beanName = transformedBeanName(name);
Object bean;

Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == n
d66e
ull) {
if (logger.isDebugEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
} else {
logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
} else {
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}

BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
String nameToLookup = originalBeanName(name);
if (args != null) {
return (T) parentBeanFactory.getBean(nameToLookup, args);
} else {
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
}

if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}

try {
//获取BeanDefinition
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);

String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
getBean(dep);
}
}

if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
try {
//创建Bean
return createBean(beanName, mbd, args);
} catch (BeansException ex) {
destroySingleton(beanName);
throw ex;
}
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
} else if (mbd.isPrototype()) {
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
} finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
} else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
} finally {
afterPrototypeCreation(beanName);
}
}
});
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
} catch (IllegalStateException ex) {
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
} catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}

if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
try {
return getTypeConverter().convertIfNecessary(bean, requiredType);
} catch (TypeMismatchException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}

protected RootBeanDefinition getMergedLocalBeanDefinition(String beanName) throws BeansException {
// Quick check on the concurrent map first, with minimal locking.
RootBeanDefinition mbd = this.mergedBeanDefinitions.get(beanName);
if (mbd != null) {
return mbd;
}
//获取BeanDefinition
return getMergedBeanDefinition(beanName, getBeanDefinition(beanName));
}

protected RootBeanDefinition getMergedBeanDefinition(String beanName, BeanDefinition bd)
throws BeanDefinitionStoreException {
//获取BeanDefinition
return getMergedBeanDefinition(beanName, bd, null);
}

protected RootBeanDefinition getMergedBeanDefinition(
String beanName, BeanDefinition bd, BeanDefinition containingBd)
throws BeanDefinitionStoreException {

synchronized (this.mergedBeanDefinitions) {
RootBeanDefinition mbd = null;

if (containingBd == null) {
mbd = this.mergedBeanDefinitions.get(beanName);
}

if (mbd == null) {
if (bd.getParentName() == null) {
// Use copy of given root bean definition.
if (bd instanceof RootBeanDefinition) {
mbd = ((RootBeanDefinition) bd).cloneBeanDefinition();
}
else {
//重新创建RootBeanDefinition
mbd = new RootBeanDefinition(bd);
}
}
else {
// Child bean definition: needs to be merged with parent.
BeanDefinition pbd;
try {
String parentBeanName = transformedBeanName(bd.getParentName());
if (!beanName.equals(parentBeanName)) {
pbd = getMergedBeanDefinition(parentBeanName);
}
else {
BeanFactory parent = getParentBeanFactory();
if (parent instanceof ConfigurableBeanFactory) {
pbd = ((ConfigurableBeanFactory) parent).getMergedBeanDefinition(parentBeanName);
}
else {
throw new NoSuchBeanDefinitionException(parentBeanName,
"Parent name '" + parentBeanName + "' is equal to bean name '" + beanName +
"': cannot be resolved without an AbstractBeanFactory parent");
}
}
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanDefinitionStoreException(bd.getResourceDescription(), beanName,
"Could not resolve parent bean definition '" + bd.getParentName() + "'", ex);
}
mbd = new RootBeanDefinition(pbd);
mbd.overrideFrom(bd);
}

if (!StringUtils.hasLength(mbd.getScope())) {
mbd.setScope(RootBeanDefinition.SCOPE_SINGLETON);
}

if (containingBd != null && !containingBd.isSingleton() && mbd.isSingleton()) {
mbd.setScope(containingBd.getScope());
}

if (containingBd == null && isCacheBeanMetadata()) {
this.mergedBeanDefinitions.put(beanName, mbd);
}
}

return mbd;
}
}
}

2.4 AbstractAutowireCapableBeanFactory提供了创建实例的方法,对应的实例又InstantiationStrategy根据策略创建

public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {

protected InstantiationStrategy getInstantiationStrategy() {
return this.instantiationStrategy;
}

@Override
protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
if (logger.isDebugEnabled()) {
logger.debug("Creating instance of bean '" + beanName + "'");
}
RootBeanDefinition mbdToUse = mbd;

Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}

try {
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}

try {
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
if (bean != null) {
return bean;
}
}
catch (Throwable ex) {
throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
"BeanPostProcessor before instantiation of bean failed", ex);
}
//创建Bean实例
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isDebugEnabled()) {
logger.debug("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
throws BeanCreationException {

BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
//创建Bean实例
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
mbd.resolvedTargetType = beanType;

synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}

boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isDebugEnabled()) {
logger.debug("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
addSingletonFactory(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
return getEarlyBeanReference(beanName, mbd, bean);
}
});
}

Object exposedObject = bean;
try {
populateBean(beanName, mbd, instanceWrapper);
if (exposedObject != null) {
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
}
catch (Throwable ex) {
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
throw (BeanCreationException) ex;
}
else {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
}
}

if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
if (exposedObject == bean) {
exposedObject = earlySingletonReference;
}
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
if (!actualDependentBeans.isEmpty()) {
throw new BeanCurrentlyInCreationException(beanName,
"Bean with name '" + beanName + "' has been injected into other beans [" +
StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
"] in its raw version as part of a circular reference, but has eventually been " +
"wrapped. This means that said other beans do not use the final version of the " +
"bean. This is often the result of over-eager type matching - consider using " +
"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}

try {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}

return exposedObject;
}

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
Class<?> beanClass = resolveBeanClass(mbd, beanName);

if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
}

if (mbd.getFactoryMethodName() != null)  {
return instantiateUsingFactoryMethod(beanName, mbd, args);
}

// Shortcut when re-creating the same bean...
boolean resolved = false;
boolean autowireNecessary = false;
if (args == null) {
synchronized (mbd.constructorArgumentLock) {
if (mbd.resolvedConstructorOrFactoryMethod != null) {
resolved = true;
autowireNecessary = mbd.constructorArgumentsResolved;
}
}
}
if (resolved) {
if (autowireNecessary) {
return autowireConstructor(beanName, mbd, null, null);
}
else {
return instantiateBean(beanName, mbd);
}
}

Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
if (ctors != null ||
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {
return autowireConstructor(beanName, mbd, ctors, args);
}

// 创建对象
return instantiateBean(beanName, mbd);
}

protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
try {
Object beanInstance;
final BeanFactory parent = this;
if (System.getSecurityManager() != null) {
beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
return getInstantiationStrategy().instantiate(mbd, beanName, parent);
}
}, getAccessControlContext());
}
else {
// 初始化对象
beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
}
//Bean包装器
BeanWrapper bw = new BeanWrapperImpl(beanInstance);
initBeanWrapper(bw);
return bw;
}
catch (Throwable ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
}
}

}

2.5 SimpleInstantiationStrategy提供了根据反射和CGLIB创建对象实例的方法

public class SimpleInstantiationStrategy implements InstantiationStrategy {

@Override
public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner) {
if (bd.getMethodOverrides().isEmpty()) {
Constructor<?> constructorToUse;
synchronized (bd.constructorArgumentLock) {
constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
if (constructorToUse == null) {
final Class<?> clazz = bd.getBeanClass();
if (clazz.isInterface()) {
throw new BeanInstantiationException(clazz, "Specified class is an interface");
}
try {
if (System.getSecurityManager() != null) {
constructorToUse = AccessController.doPrivileged(new PrivilegedExceptionAction<Constructor<?>>() {
@Override
public Constructor<?> run() throws Exception {
return clazz.getDeclaredConstructor((Class[]) null);
}
});
}
else {
//获取默认构造函数
constructorToUse =  clazz.getDeclaredConstructor((Class[]) null);
}
bd.resolvedConstructorOrFactoryMethod = constructorToUse;
}
catch (Throwable ex) {
throw new BeanInstantiationException(clazz, "No default constructor found", ex);
}
}
}
//创建对象
return BeanUtils.instantiateClass(constructorToUse);
}
else {
return instantiateWithMethodInjection(bd, beanName, owner);
}
}
}

2.6 BeanUtils负责根据反射创建对象

public abstract class BeanUtils {

public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException {
Assert.notNull(ctor, "Constructor must not be null");
try {
ReflectionUtils.makeAccessible(ctor);
//通过反射创建对象
return ctor.newInstance(args);
}
catch (InstantiationException ex) {
throw new BeanInstantiationException(ctor, "Is it an abstract class?", ex);
}
catch (IllegalAccessException ex) {
throw new BeanInstantiationException(ctor, "Is the constructor accessible?", ex);
}
catch (IllegalArgumentException ex) {
throw new BeanInstantiationException(ctor, "Illegal arguments for constructor", ex);
}
catch (InvocationTargetException ex) {
throw new BeanInstantiationException(ctor, "Constructor threw exception", ex.getTargetException());
}
}
}