标签：logger == col 企业应用 开发 对象 path war img
IoC 和 AOP是Spring的核心， 是Spring系统中其他组件模块和应用开发的基础。透过这两个模块的设计和实现可以了解Spring倡导的对企业应用开发所应秉承的思路：
IoC和AOP这两个核心组件，特别是IoC容器，使用户在使用Spring完成POJO应用开发的过程中必须使用的。这样的应用策略也极大的扩展了Spring的应用场合，不仅包括Java EE应用，还包括其他方面的应用，比如桌面等。从这个意义上讲，IoC容器称得上是Spring的最核心部分。
Agenda：
2004年Martin Fowler提出“哪些方面被反转了”，得出的结论“依赖对象的获得被反转了”。控制反转概念在Spring中通过依赖注入实现。
IoC容器，把资源获取的方向反转，让IoC容器主动管理这些依赖关系，将这些依赖关系注入到组件中，让依赖关系的是配合管理更加灵活。
具体的注入实现中，接口注入（Type 1 IoC），setter注入（Type 2 IoC），构造器注入（Type 3 IoC），后两种是主要的；为了防止注入异常，Spring还提供了对特定依赖的检查。
Spring IoC容器已经不是原来简单的Interface21框架了，已经成为一个IoC容器的工业级实现。下面，我们会对IoC容器系列的设计和实现进行详细分析。
IoC容器主要系列： 一个是实现BeanFactory接口的简单容器系列，这系列之实现了容器的最基本功能； 另一个是ApplicationContext应用上下文，作为容器的高级形态而存在。
BeanDefinition来管理对象以及之间的相互依赖关系：
BeanDefinition像是容器里的水，BeanFactory是容器。
BeanFactory 到 HierarchicalBeanFactory 再到ConfigureBeanFactory，是一条主要的设计路径. HierarchicalBeanFactory定义了getparentBeanFactory的功能，具备了双亲IoC容器的管理功能； ConfigureBeanFactory增加了一些配置功能，比如setParentBeanFactory设置双亲容器，addBeanPostProcessor配置后置处理器；
第二条接口设计主线是，以ApplicationContext应用上下文接口为核心的接口设计。 ListableBeanFactory细化了许多BeanFactory功能；
以XmlBeanFactory实现为例说明简单IoC容器的设计原理。下图为XmlBeanFactory设计的类继承关系：
编程式使用IoC容器：
ClassPathResource res = new ClassPathResource("first.xml");
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
reader.loadBeanDefinitions(res);
HelloBean helloBean = (HelloBean) factory.getBean("hello")；
在BeanFactory的基础上添加的附加功能:
以FileSystemXmlApplicationContext为例说明设计原理，FileSystemXmlApplicationContext的基类AbstractXmlApplicationContext中实现了，作为一个具体的应用上下文，只需要实现和他自身设计相关的两个功能：
public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent) throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
protected Resource getResourceByPath(String path) {
if (path != null && path.startsWith("/")) {
path = path.substring(1);
}
return new FileSystemResource(path);
}
以下是AbstractApplicationContext.refresh()方法的具体内容
// 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();
}
}
IoC容器的初始化是由refresh方法来完成启动的。具体来讲，这个启动包括BeanDefinition的Resource定位、载入和注册。
public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {
// 1 获取资源加载器；资源路径解析；系统属性设置
super(parent);
// 2 设定加载位置；解析加载路径
setConfigLocations(configLocations);
if (refresh) {
// 3 载入BeanDefinition，并注册
refresh();
}
}
在步骤1，2完成资源的定位
针对以上例子，得出Spring解析xml文件的流程图和结构图：
承担载入和解析任务为refresh方法中的obtainFreshBeanFactory方法。 AbstractXmlApplicationContext.loadBeanDefinitions来载入BeanDefinition。
Spring解析配置文件中用到的一些关键类的介绍：
源码一：加载XML
AbstractXmlApplicationContext:
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);
}
---
XmlBeanDefinitionReader:
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
//加载xml资源
return loadBeanDefinitions(new EncodedResource(resource));
}
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
//设置字符集
inputSource.setEncoding(encodedResource.getEncoding());
}
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
}
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
int validationMode = getValidationModeForResource(resource);
//根据xml文件，得到标准的Document对象
//EntityResolver 主要用做验证用，可参考http://www.cnblogs.com/mjorcen/p/3642855.html
Document doc = this.documentLoader.loadDocument(
inputSource, getEntityResolver(), this.errorHandler, validationMode, isNamespaceAware());
return registerBeanDefinitions(doc, resource);
}
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
//BeanDefinitionDocumentReader实际解析doc文档
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}
源码二：元素解析
DefaultBeanDefinitionDocumentReader:
protected void doRegisterBeanDefinitions(Element root) {
BeanDefinitionParserDelegate parent = this.delegate;
//元素解析的代理类，主要的bean解析，以及一些自定义元素的解析
this.delegate = createDelegate(this.readerContext, root, parent);
...
//默认为空操作
preProcessXml(root);
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);
this.delegate = parent;
}
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
//默认命名空间为http://www.springframework.org/schema/beans，也就是xml文件中<bean>的标签
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)) {
//处理默认<bean>标签
parseDefaultElement(ele, delegate);
}
else {
//处理自定义标签 (i.e. AOP,CONTENT,JDBC)
delegate.parseCustomElement(ele);
}
}
}
}
else {//处理自定义标签
delegate.parseCustomElement(root);
}
}
源码三：基本元素解析
DefaultBeanDefinitionDocumentReader // 默认标签处理
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
// import tag
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
// alias tag
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
// bean tag
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
// beans tag （嵌套import／alias／bean）
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//解析element，得到BeanDefinition，BeanDefinitionHolder中包含了BeanDefinition
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));
}
}
---
BeanDefinitionParserDelegate:
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<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 (containingBean == null) {
//检查bean name的唯一性. 如果usedNames不存在时，则加入usedNames，否则抛出重名异常
checkNameUniqueness(beanName, aliases, ele);
}
//解析Element,真正解析<bean>的地方
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
if (beanDefinition != null) {
.....
String[] aliasesArray = StringUtils.toStringArray(aliases);
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
}
return null;
}
源码四：处理扩展或自定义标签
BeanDefinitionParserDelegate：
public BeanDefinition parseCustomElement(Element ele) {
return parseCustomElement(ele, null);
}
public BeanDefinition parseCustomElement(Element ele, BeanDefinition containingBd) {
String namespaceUri = getNamespaceURI(ele);
//根据元素的命名空间得到NamespaceHandler
NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
if (handler == null) {
error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", ele);
return null;
}
//使用合适的NamespaceHandler解析元素
return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
}
NamespaceHandlerSupport：
public BeanDefinition parse(Element element, ParserContext parserContext) {
return findParserForElement(element, parserContext).parse(element, parserContext);
}
源码四、一：处理扩展或自定义标签的处理类何处加载
在上面{NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri)}这句话加载
BeanDefinitionParserDelegate：
public BeanDefinition parseCustomElement(Element ele, BeanDefinition containingBd) {
String namespaceUri = getNamespaceURI(ele);
// 加载自定义标签处理类
NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
....
}
DefaultNamespaceHandlerResolver：
public NamespaceHandler resolve(String namespaceUri) {
//得到Map<Element名称，NamespaceHandler处理类>
Map<String, Object> handlerMappings = getHandlerMappings();
//根据namespaceUri得到匹配的NamespaceHandler
Object handlerOrClassName = handlerMappings.get(namespaceUri);
if (handlerOrClassName == null) {
return null;
}
else if (handlerOrClassName instanceof NamespaceHandler) {
return (NamespaceHandler) handlerOrClassName;
}
else {
String className = (String) handlerOrClassName;
.....
}
}
private Map<String, Object> getHandlerMappings() {
if (this.handlerMappings == null) {
synchronized (this) {
if (this.handlerMappings == null) {
try {
//handlerMappingsLocation默认值：META-INF/spring.handlers
//spring就会从jar包中的Meta-INF/spring.handlers文件中得到处理各种不同命名空间元素的类
Properties mappings =
PropertiesLoaderUtils.loadAllProperties(this.handlerMappingsLocation, this.classLoader);
if (logger.isDebugEnabled()) {
logger.debug("Loaded NamespaceHandler mappings: " + mappings);
}
Map<String, Object> handlerMappings = new ConcurrentHashMap<String, Object>(mappings.size());
CollectionUtils.mergePropertiesIntoMap(mappings, handlerMappings);
this.handlerMappings = handlerMappings;
}
catch (IOException ex) {
throw new IllegalStateException(
"Unable to load NamespaceHandler mappings from location [" + this.handlerMappingsLocation + "]", ex);
}
}
}
}
return this.handlerMappings;
}
Spring是如何解析自定义元素(i.e.
DefaultListableBeanFactory:
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
....
BeanDefinition oldBeanDefinition;
oldBeanDefinition = this.beanDefinitionMap.get(beanName);
if (oldBeanDefinition != null) {
....
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<String>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames);
updatedSingletons.remove(beanName);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// Still in startup registration phase
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
this.manualSingletonNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (oldBeanDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}
参考： http://www.blogjava.net/heavensay/archive/2013/10/28/405699.html http://kyfxbl.iteye.com/blog/1610255 (小读spring ioc源码) http://blog.csdn.net/cutesource/article/details/5864562 (基于Spring可扩展Schema提供自定义配置支持)
原文:大专栏 SPRING源码解析－SPRING 核心－IOC
标签：logger == col 企业应用 开发 对象 path war img
原文地址：https://www.cnblogs.com/petewell/p/11615224.html
