服务器启动,加载web.xml 文件的时候发现监听器:ContextLoaderListener
初始化监听器
1所以调用contextInitialized方法
@Override
public void contextInitialized(ServletContextEvent event) {
initWebApplicationContext(event.getServletContext());
}
initWebApplicationContext 代码如下
public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
if (this.context instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context;
if (!cwac.isActive()) {
// The context has not yet been refreshed -> provide services such as
// setting the parent context, setting the application context id, etc
if (cwac.getParent() == null) {
// The context instance was injected without an explicit parent ->
// determine parent for root web application context, if any.
ApplicationContext parent = loadParentContext(servletContext);
cwac.setParent(parent);
}
configureAndRefreshWebApplicationContext(cwac, servletContext);
}
}
。。。。。。
return this.context;
}
}
2调用了configureAndRefreshWebApplicationContext方法:
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {
。。。。。
wac.refresh();
}
3调用refresh()方法:
@Override
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();
。。。。。。。。
}
}
4 调用obtainFreshBeanFactory()方法
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
5 之后调用到refreshBeanFactory()方法
@Override
protected final void refreshBeanFactory() throws BeansException {
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
6 调用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(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);
}
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws IOException {
String[] configLocations = getConfigLocations();
if (configLocations != null) {
for (String configLocation : configLocations) {
reader.loadBeanDefinitions(configLocation);
}
}
}
Spring加载资源分析
说明:
这篇文档是对Spring加载和解析xml文件过程的分析,下面看一个spring解析xml文件的测试例子。
@Test
public void test3BeanDefinitionReader(){
DefaultResourceLoader loader = new DefaultResourceLoader();
Resource resource = loader.getResource("/ioc/application.xml");
BeanDefinitionRegistry registry = new SimpleBeanDefinitionRegistry();
BeanDefinitionReader reader = new XmlBeanDefinitionReader(registry);
int count = reader.loadBeanDefinitions(resource);
String[] beanDefinitionNames = reader.getRegistry().getBeanDefinitionNames();
System.out.println("----------------------");
for (String name : beanDefinitionNames) {
System.out.println(name);
}
}
大概的逻辑:先读取文件放到doc 里,然后 解析doc ,一个元素一个元素,拿出来,解析 生成 bean ,然后放入registry 中。
Spring解析配置文件中用到的一些关键类的介绍:
Resource:各种资源的抽象接口,包括xml文件,网络上的资源等。
BeanDefinitionRegistry:用于注册Bean。
BeanDefinitionReader:用于读取解析Resource的抽象接口。
DefaultBeanDefinitionDocumentReader:实现了BeanDefinitionDocumentReader接口,DefaultBeanDefinitionDocumentReader并不负责任何具体的bean解析,它面向的是xml Document对象,根据其元素的命名空间和名称,起一个类似路由的作用((不过,命名空间的判断,也是委托给delegate来做的),它跟BeanDefinitionParserDelegate协同合作,把解析任务交接BeanDefinitionParserDelegate来做。
BeanDefinitionParserDelegate:完成具体Bean的解析(比如<bean>、<import>、<alias>标签),对于扩展的标签会交给不同的NamespaceHandler跟BeanDefinitionParser来解析。
BeanDefinitionParser:解析配置文件成相应的BeanDefinition(<context:component-scan>,<aop:config>等标签都是又不同的BeanDefinitionParser来解析),一般在NamespaceHandler中使用。Spring也为自定义BeanDefinitionParser提供了很多支持,在一些抽象类的基础上添加少量功能即可满足大部分需求。
NamespaceHandler:要解析自定义的bean就要通过自己所实现的NamespaceHandler来进行解析。比如定义了http\://www.springframework.org/schema/osgi=org.springframework.osgi.config.OsgiNamespaceHandler,那么在碰到osgi的scheme的时候就会去调用OsgiNamespaceHandler来进行解析; 在对于普通的扩展需求来说,只要让自己的Handler继承NamespaceHandlerSupport并实现 init()方法 就好了,对于特殊的扩展需求 则可以自己 来实现NamespaceHandler。
下面来分析一下源代码:
源码1:加载xml文件
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
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;
}
DefaultBeanDefinitionDocumentReader:
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
Element root = doc.getDocumentElement();
//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
BeanDefinitionParserDelegate delegate = createHelper(readerContext, root);
//默认为空操作
preProcessXml(root);
//解析元素
parseBeanDefinitions(root, delegate);
postProcessXml(root);
}
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2:基本元素解析(i.e. <bean>、<import>......)
DefaultBeanDefinitionDocumentReader:
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
//解析<import>标签
importBeanDefinitionResource(ele);
}
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
//解析<alias>标签
processAliasRegistration(ele);
}
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
//解析<bean>标签
processBeanDefinition(ele, delegate);
}
}
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//解析element,得到BeanDefinition,BeanDefinitionHolder中包含了BeanDefinition
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
//注册BeanDefinition
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
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, BEAN_NAME_DELIMITERS);
aliases.addAll(Arrays.asList(nameArr));
}
String beanName = id;
if (containingBean == null) {
//检查bean name的唯一性
checkNameUniqueness(beanName, aliases, ele);
}
//解析Element
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
if (beanDefinition != null) {
String[] aliasesArray = StringUtils.toStringArray(aliases);
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
}
return null;
}
//真正解析<bean>的地方
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();
}
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
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);
bd.setResource(this.readerContext.getResource());
bd.setSource(extractSource(ele));
return bd;
return null;
}
源码3: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);
//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) {
//得到真正具体处理自定义的BeanDefinitionParser,解析element得到BeanDefinition
return findParserForElement(element, parserContext).parse(element, parserContext);
}
private BeanDefinitionParser findParserForElement(Element element, ParserContext parserContext) {
String localName = parserContext.getDelegate().getLocalName(element);
//parsers中包含了具体处理自定义标签的类
BeanDefinitionParser parser = this.parsers.get(localName);
return parser;
}
代码3.2:在源码3.1中代码:{NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri)}这步中,展示了对于扩展或自定义的标签的处理类是从哪里加载的
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{
}
}
private Map<String, Object> getHandlerMappings() {
//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);
Map<String, Object> handlerMappings = new ConcurrentHashMap<String, Object>();
CollectionUtils.mergePropertiesIntoMap(mappings, handlerMappings);
this.handlerMappings = handlerMappings;
return this.handlerMappings;
}
当初一直在想Spring是如何解析自定义元素(i.e. <context:component-scan>,<aop:config> )。通过源码分析看出spring在解析的过程中,会去收集spring.*.jar/META-INF下的spring.handers,spring.schemas文件,这2个文件就是指明了解析spring中自定义标签的Namespace类。如果自己开发Spring组件,需要增加新的标签,也可以按照这个机制。