首先从WEB.XML入手
==>web.xml
代码
<context-param>
<param-name>webAppRootKey</param-name>
<param-value>task.root</param-value>
</context-param>
<!-- 定义SPRING配置文件 -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/taskContext*.xml</param-value>
</context-param>
</span>
<context-param>
<param-name>log4jConfigLocation</param-name>
<param-value>/WEB-INF/log4j.properties</param-value>
</context-param>
<!-- 定义LOG4J监听器 -->
<listener>
<listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
</listener>
<!-- 定义SPRING监听器 -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
进入contextLoaderListener看看到底加载时做了甚么
==>org.springframework.web.context.ContextLoaderListener
代码
public class ContextLoaderListener implements ServletContextListener {
private ContextLoader contextLoader;
/**
* Initialize the root web application context.
*/
//当WEB上下文初始化时,系统会调用此方法
public void contextInitialized(ServletContextEvent event) {
this.contextLoader = createContextLoader();
//监听到WEB上下文初始化的时候执行SPRING上下文contextLoader的初始化工作
this.contextLoader.initWebApplicationContext(event.getServletContext());
}
/**
* Create the ContextLoader to use. Can be overridden in subclasses.
* @return the new ContextLoader
*/
protected ContextLoader createContextLoader() {
return new ContextLoader();
}
/**
* Return the ContextLoader used by this listener.
*/
public ContextLoader getContextLoader() {
return contextLoader;
}
/**
* Close the root web application context.
*/
public void contextDestroyed(ServletContextEvent event) {
if (this.contextLoader != null) {
this.contextLoader.closeWebApplicationContext(event.getServletContext());
}
}
}
看一下是怎么来初始化webapplicationContext的
==>contextLoader.initWebApplicationContext
代码
public WebApplicationContext initWebApplicationContext(ServletContext servletContext)
throws IllegalStateException, BeansException {
if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
throw new IllegalStateException(
"Cannot initialize context because there is already a root application context
present - " +
"check whether you have multiple ContextLoader* definitions in your web.xml!");
}
long startTime = System.currentTimeMillis();
if (logger.isInfoEnabled()) {
logger.info("Root WebApplicationContext: initialization started");
}
servletContext.log("Loading Spring root WebApplicationContext");
try {
// Determine parent for root web application context, if any.
ApplicationContext parent = loadParentContext(servletContext);
// Store context in local instance variable, to guarantee that
// it is available on ServletContext shutdown.
//创建web上下文
this.context = createWebApplicationContext(servletContext, parent);
servletContext.setAttribute(
WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
if (logger.isInfoEnabled()) {
logger.info("Using context class [" + this.context.getClass().getName() +
"] for root WebApplicationContext");
}
if (logger.isDebugEnabled()) {
logger.debug("Published root WebApplicationContext [" + this.context +
"] as ServletContext attribute with name [" +
WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
}
if (logger.isInfoEnabled()) {
long elapsedTime = System.currentTimeMillis() - startTime;
logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + "
ms");
}
return this.context;
}
catch (RuntimeException ex) {
logger.error("Context initialization failed", ex);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
throw ex;
}
catch (Error err) {
logger.error("Context initialization failed", err);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err);
throw err;
}
}
==>contextLoader.createWebApplicationContext(servletContext, parent);
代码
protected WebApplicationContext createWebApplicationContext(
ServletContext servletContext, ApplicationContext parent) throws BeansException {
//根据servletContext来决定要实例化的WebApplicationContext
Class contextClass = determineContextClass(servletContext);
if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
throw new ApplicationContextException("Custom context class [" + contextClass.getName() +
"] is not of type ConfigurableWebApplicationContext");
}
ConfigurableWebApplicationContext wac =
(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
wac.setParent(parent);
wac.setServletContext(servletContext);
//得到WEB.XML中设置的SPRING配置文件位置
String configLocation = servletContext.getInitParameter(CONFIG_LOCATION_PARAM);
if (configLocation != null) {
//把配置文件分段后设置到WebApplicationContext的ConfigLocations中
wac.setConfigLocations(StringUtils.tokenizeToStringArray(configLocation,
ConfigurableWebApplicationContext.CONFIG_LOCATION_DELIMITERS));
}
//刷新WebApplicationContext
wac.refresh();
return wac;
}
==>contextLoader.determineContextClass(servletContext);
代码
protected Class determineContextClass(ServletContext servletContext) throws ApplicationContextException {
//获得需要实例化的CONTEXT类名,在web.xml中有设置,如果没有设置,那么为空
String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM);
if (contextClassName != null) {
try {
return ClassUtils.forName(contextClassName);
}
catch (ClassNotFoundException ex) {
throw new ApplicationContextException(
"Failed to load custom context class [" + contextClassName + "]", ex);
}
}
//如果在spring web.xml中没有设置context类位置,那么取得默认context
else {
//取得defaultStrategies配置文件中的WebApplicationContext属性
contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName());
try {
return ClassUtils.forName(contextClassName);
}
catch (ClassNotFoundException ex) {
throw new ApplicationContextException(
"Failed to load default context class [" + contextClassName + "]", ex);
}
}
}
SPRING上下文默认的策略是甚么呢?
==>contextLoader.defaultStrategies
代码
private static final Properties defaultStrategies;
static {
// Load default strategy implementations from properties file.
// This is currently strictly internal and not meant to be customized
// by application developers.
try {
//设置classpath为contextLoader同级目录
ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader.class);
//加载该目录下的所有properties文件
defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
}
catch (IOException ex) {
throw new IllegalStateException("Could not load 'ContextLoader.properties': " + ex.getMessage());
}
}
找到同级目录下的配置文件
==>ContextLoader.properties
代码
# Default WebApplicationContext implementation class for ContextLoader.
# Used as fallback when no explicit context implementation has been specified as context-param.
# Not meant to be customized by application developers.
#默认的WebApplicationContext为org.springframework.web.context.support.XmlWebApplicationContext
org.springframework.web.context.WebApplicationContext=org.springframework.web.context.support.XmlWebApplicationContext
==>org.springframework.web.context.support.XmlWebApplicationContext
代码
public class XmlWebApplicationContext extends AbstractRefreshableWebApplicationContext {
/** Default config location for the root context */
//配置了默认的spring配置文件
public static final String DEFAULT_CONFIG_LOCATION = "/WEB-INF/applicationContext.xml";
//配置文件默认BUILD路径
public static final String DEFAULT_CONFIG_LOCATION_PREFIX = "/WEB-INF/";
//配置文件默认后缀名
public static final String DEFAULT_CONFIG_LOCATION_SUFFIX = ".xml";
/**
* Loads the bean definitions via an XmlBeanDefinitionReader.
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
* @see #initBeanDefinitionReader
* @see #loadBeanDefinitions
*/
//获得bean配置
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws IOException {
//从BEAN工厂获得一个XmlBeanDefinitionReader 来读取SPRING配置文件
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
//设置beanDefinitionReader服务于当前CONTEXT
// resource loading environment.
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);
//读取配置文件
loadBeanDefinitions(beanDefinitionReader);
}
/**
* Initialize the bean definition reader used for loading the bean
* definitions of this context. Default implementation is empty.
* <p>Can be overridden in subclasses, e.g. for turning off XML validation
* or using a different XmlBeanDefinitionParser implementation.
* @param beanDefinitionReader the bean definition reader used by this context
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader#setValidationMode
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader#setDocumentReaderClass
*/
protected void initBeanDefinitionReader(XmlBeanDefinitionReader beanDefinitionReader) {
}
/**
* Load the bean definitions with the given XmlBeanDefinitionReader.
* <p>The lifecycle of the bean factory is handled by the refreshBeanFactory method;
* therefore this method is just supposed to load and/or register bean definitions.
* <p>Delegates to a ResourcePatternResolver for resolving location patterns
* into Resource instances.
* @throws org.springframework.beans.BeansException in case of bean registration errors
* @throws java.io.IOException if the required XML document isn't found
* @see #refreshBeanFactory
* @see #getConfigLocations
* @see #getResources
* @see #getResourcePatternResolver
*/
//读取配置文件
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
String[] configLocations = getConfigLocations();
if (configLocations != null) {
for (int i = 0; i < configLocations.length; i++) {
reader.loadBeanDefinitions(configLocations[i]);
}
}
}
/**
* The default location for the root context is "/WEB-INF/applicationContext.xml",
* and "/WEB-INF/test-servlet.xml" for a context with the namespace "test-servlet"
* (like for a DispatcherServlet instance with the servlet-name "test").
*/
//获得默认的ConfigLocations
protected String[] getDefaultConfigLocations() {
if (getNamespace() != null) {
return new String[] {DEFAULT_CONFIG_LOCATION_PREFIX + getNamespace() +
DEFAULT_CONFIG_LOCATION_SUFFIX};
}
else {
return new String[] {DEFAULT_CONFIG_LOCATION};
}
}
==>AbstractBeanDefinitionReader.loadBeanDefinitions()
代码
public int loadBeanDefinitions(String location) 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 {
//根据配置文件读取相应配置
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
int loadCount = loadBeanDefinitions(resources);
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 (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
}
return loadCount;
}
}
这个是其中一个ResourceLoader的实现
==>PathMatchingResourcePatternResolver.getResources(String locationPattern);
代码
public Resource[] getResources(String locationPattern) throws IOException {
Assert.notNull(locationPattern, "Location pattern must not be null");
if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) {
// a class path resource (multiple resources for same name possible)
if (getPathMatcher().isPattern(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()))) {
// a class path resource pattern
return findPathMatchingResources(locationPattern);
}
else {
// all class path resources with the given name
return findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()));
}
}
else {
// Only look for a pattern after a prefix here
// (to not get fooled by a pattern symbol in a strange prefix).
int prefixEnd = locationPattern.indexOf(":") + 1;
if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {
// a file pattern
return findPathMatchingResources(locationPattern);
}
else {
// a single resource with the given name
return new Resource[] {getResourceLoader().getResource(locationPattern)};
}
}
}
==>PathMatchingResourcePatternResolver.findPathMatchingResources(String locationPattern);
代码
protected Resource[] findPathMatchingResources(String locationPattern) throws IOException {
String rootDirPath = determineRootDir(locationPattern);
String subPattern = locationPattern.substring(rootDirPath.length());
Resource[] rootDirResources = getResources(rootDirPath);
//collectionFactory初始化一个set容量为16
Set result = CollectionFactory.createLinkedSetIfPossible(16);
for (int i = 0; i < rootDirResources.length; i++) {
Resource rootDirResource = rootDirResources[i];
if (isJarResource(rootDirResource)) {
result.addAll(doFindPathMatchingJarResources(rootDirResource, subPattern));
}
else {
result.addAll(doFindPathMatchingFileResources(rootDirResource, subPattern));
}
}
if (logger.isDebugEnabled()) {
logger.debug("Resolved location pattern [" + locationPattern + "] to resources " + result);
}
return (Resource[]) result.toArray(new Resource[result.size()]);
}
前面说到有一个刷新WebApplicationContext的操作,但是XmlWebApplicationContext 并没有实现refresh方法,而方法的实现写在
AbstractRefreshableWebApplicationContext 中
==>AbstractRefreshableWebApplicationContext.refresh();
代码
public void refresh() throws BeansException {
if (ObjectUtils.isEmpty(getConfigLocations())) {
//设置configLocations为默认的getDefaultConfigLocations()
setConfigLocations(getDefaultConfigLocations());
}
super.refresh();
}
==>AbstractApplicationContext.refresh();
代码
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
this.startupTime = System.currentTimeMillis();
synchronized (this.activeMonitor) {
this.active = true;
}
// Tell subclass to refresh the internal bean factory.
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// Tell the internal bean factory to use the context's class loader.
beanFactory.setBeanClassLoader(getClassLoader());
// Populate the bean factory with context-specific resource editors.
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this));
// Configure the bean factory with context semantics.
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered with the context instance.
for (Iterator it = getBeanFactoryPostProcessors().iterator(); it.hasNext();) {
BeanFactoryPostProcessor factoryProcessor = (BeanFactoryPostProcessor) it.next();
factoryProcessor.postProcessBeanFactory(beanFactory);
}
if (logger.isInfoEnabled()) {
if (getBeanDefinitionCount() == 0) {
logger.info("No beans defined in application context [" + getDisplayName() + "]");
}
else {
logger.info(getBeanDefinitionCount() + " beans defined in application context [" +
getDisplayName() + "]");
}
}
try {
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors();
// Register bean processors that intercept bean creation.
registerBeanPostProcessors();
// 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 singletons this late to allow them to access the message source.
beanFactory.preInstantiateSingletons();
// Last step: publish corresponding event.
publishEvent(new ContextRefreshedEvent(this));
}
catch (BeansException ex) {
// Destroy already created singletons to avoid dangling resources.
beanFactory.destroySingletons();
throw ex;
}
}
}