Spring源码（一）

<listener>
　　<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

ContextLoaderListener.java

public class ContextLoaderListener extends ContextLoader implements ServletContextListener {
    public ContextLoaderListener() {
    }

    public ContextLoaderListener(WebApplicationContext context) {
        super(context);
    }
　　// 应用启动会触发此方法，ServletContextListener中会进行监听触发
    public void contextInitialized(ServletContextEvent event) {
        this.initWebApplicationContext(event.getServletContext());
    }

    public void contextDestroyed(ServletContextEvent event) {
        this.closeWebApplicationContext(event.getServletContext());
        ContextCleanupListener.cleanupAttributes(event.getServletContext());
    }
}

ContextLoader.java

public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
        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!");
        } else {
            Log logger = LogFactory.getLog(ContextLoader.class);
            servletContext.log("Initializing Spring root WebApplicationContext");
            if (logger.isInfoEnabled()) {
                logger.info("Root WebApplicationContext: initialization started");
            }

            long startTime = System.currentTimeMillis();

            try {
                if (this.context == null) {
                    this.context = this.createWebApplicationContext(servletContext);
                }

                if (this.context instanceof ConfigurableWebApplicationContext) {
                    ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext)this.context;
                    if (!cwac.isActive()) {
                        if (cwac.getParent() == null) {
                            ApplicationContext parent = this.loadParentContext(servletContext);
                            cwac.setParent(parent);
                        }

                        this.configureAndRefreshWebApplicationContext(cwac, servletContext);
                    }
                }

                servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
                ClassLoader ccl = Thread.currentThread().getContextClassLoader();
                if (ccl == ContextLoader.class.getClassLoader()) {
                    currentContext = this.context;
                } else if (ccl != null) {
                    currentContextPerThread.put(ccl, this.context);
                }

                if (logger.isDebugEnabled()) {
                    logger.debug("Published root WebApplicationContext 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 var8) {
                logger.error("Context initialization failed", var8);
                servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, var8);
                throw var8;
            } catch (Error var9) {
                logger.error("Context initialization failed", var9);
                servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, var9);
                throw var9;
            }
        }
    }

  protected WebApplicationContext createWebApplicationContext(ServletContext sc) {
        Class<?> contextClass = this.determineContextClass(sc);
        if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
            throw new ApplicationContextException("Custom context class [" + contextClass.getName() + "] is not of type [" + ConfigurableWebApplicationContext.class.getName() + "]");
        } else {
            // 日后的开发中可以借鉴这个方法，利用工具类去生成对象，避免重复造车
            return (ConfigurableWebApplicationContext)BeanUtils.instantiateClass(contextClass);
        }
    }

ContextLoader.java的静态代码块加载解析property

 static {
        try {
            ClassPathResource resource = new ClassPathResource("ContextLoader.properties", ContextLoader.class);
            defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
        } catch (IOException var1) {
            throw new IllegalStateException("Could not load 'ContextLoader.properties': " + var1.getMessage());
        }

        currentContextPerThread = new ConcurrentHashMap(1);
    }

org.springframework.web.context.WebApplicationContext=org.springframework.web.context.support.XmlWebApplicationContext

protected Class<?> determineContextClass(ServletContext servletContext) {
        String contextClassName = servletContext.getInitParameter("contextClass");
        if (contextClassName != null) {
            try {
                return ClassUtils.forName(contextClassName, ClassUtils.getDefaultClassLoader());
            } catch (ClassNotFoundException var4) {
                throw new ApplicationContextException("Failed to load custom context class [" + contextClassName + "]", var4);
            }
        } else {
            contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName());

            try {
                return ClassUtils.forName(contextClassName, ContextLoader.class.getClassLoader());
            } catch (ClassNotFoundException var5) {
                throw new ApplicationContextException("Failed to load default context class [" + contextClassName + "]", var5);
            }
        }
    }

protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {
    String configLocationParam;
    if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
        configLocationParam = sc.getInitParameter("contextId");
        if (configLocationParam != null) {
            wac.setId(configLocationParam);
        } else {
            wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + ObjectUtils.getDisplayString(sc.getContextPath()));
        }
    }

    wac.setServletContext(sc);
    configLocationParam = sc.getInitParameter("contextConfigLocation");
    if (configLocationParam != null) {
        wac.setConfigLocation(configLocationParam);
    }

    ConfigurableEnvironment env = wac.getEnvironment();
    if (env instanceof ConfigurableWebEnvironment) {
        ((ConfigurableWebEnvironment)env).initPropertySources(sc, (ServletConfig)null);
    }

    this.customizeContext(sc, wac);
    wac.refresh();
}

public void refresh() throws BeansException, IllegalStateException {
    synchronized(this.startupShutdownMonitor) {
        this.prepareRefresh();
        ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
        this.prepareBeanFactory(beanFactory);

        try {
            this.postProcessBeanFactory(beanFactory);
            this.invokeBeanFactoryPostProcessors(beanFactory);
            this.registerBeanPostProcessors(beanFactory);
            this.initMessageSource();
            this.initApplicationEventMulticaster();
            this.onRefresh();
            this.registerListeners();
            this.finishBeanFactoryInitialization(beanFactory);
            this.finishRefresh();
        } catch (BeansException var9) {
            if (this.logger.isWarnEnabled()) {
                this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt: " + var9);
            }

            this.destroyBeans();
            this.cancelRefresh(var9);
            throw var9;
        } finally {
            this.resetCommonCaches();
        }

    }
}

protected void prepareRefresh() {
    this.startupDate = System.currentTimeMillis();
    this.closed.set(false);
    this.active.set(true);
    if (this.logger.isInfoEnabled()) {
        this.logger.info("Refreshing " + this);
    }

    this.initPropertySources();
    this.getEnvironment().validateRequiredProperties();
    this.earlyApplicationEvents = new LinkedHashSet();
}

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

    return beanFactory;
}

protected final void refreshBeanFactory() throws BeansException {
    if (this.hasBeanFactory()) {
        this.destroyBeans();
        this.closeBeanFactory();
    }

    try {
        DefaultListableBeanFactory beanFactory = this.createBeanFactory();
        beanFactory.setSerializationId(this.getId());
        this.customizeBeanFactory(beanFactory);
        this.loadBeanDefinitions(beanFactory);
        synchronized(this.beanFactoryMonitor) {
            this.beanFactory = beanFactory;
        }
    } catch (IOException var5) {
        throw new ApplicationContextException("I/O error parsing bean definition source for " + this.getDisplayName(), var5);
    }
}
-----------------------------------------------------------------------------------------------------------------------

XmlWebApplicationContext.java

@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);
}

/**
 * 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 IOException if the required XML document isn't found
 * @see #refreshBeanFactory
 * @see #getConfigLocations
 * @see #getResources
 * @see #getResourcePatternResolver
 */
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws IOException {
   String[] configLocations = getConfigLocations();
   if (configLocations != null) {
      for (String configLocation : configLocations) {
         reader.loadBeanDefinitions(configLocation);
      }
   }
}

/**
 * Load bean definitions from the specified resource location.
 * <p>The location can also be a location pattern, provided that the
 * ResourceLoader of this bean definition reader is a ResourcePatternResolver.
 * @param location the resource location, to be loaded with the ResourceLoader
 * (or ResourcePatternResolver) of this bean definition reader
 * @param actualResources a Set to be filled with the actual Resource objects
 * that have been resolved during the loading process. May be {@code null}
 * to indicate that the caller is not interested in those Resource objects.
 * @return the number of bean definitions found
 * @throws BeanDefinitionStoreException in case of loading or parsing errors
 * @see #getResourceLoader()
 * @see #loadBeanDefinitions(org.springframework.core.io.Resource)
 * @see #loadBeanDefinitions(org.springframework.core.io.Resource[])
 */
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 {
      // Can only load single resources by absolute URL.
      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;
   }
}

/**
 * Load bean definitions from the specified XML file.
 * @param encodedResource the resource descriptor for the XML file,
 * allowing to specify an encoding to use for parsing the file
 * @return the number of bean definitions found
 * @throws BeanDefinitionStoreException in case of loading or parsing errors
 */
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());
         }
         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();
      }
   }
}

/**
 * Actually load bean definitions from the specified XML file.
 * @param inputSource the SAX InputSource to read from
 * @param resource the resource descriptor for the XML file
 * @return the number of bean definitions found
 * @throws BeanDefinitionStoreException in case of loading or parsing errors
 * @see #doLoadDocument
 * @see #registerBeanDefinitions
 */
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
      throws BeanDefinitionStoreException {
   try {
      Document doc = doLoadDocument(inputSource, resource);
      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);
   }
}

/**
 * Register the bean definitions contained in the given DOM document.
 * Called by {@code loadBeanDefinitions}.
 * <p>Creates a new instance of the parser class and invokes
 * {@code registerBeanDefinitions} on it.
 * @param doc the DOM document
 * @param resource the resource descriptor (for context information)
 * @return the number of bean definitions found
 * @throws BeanDefinitionStoreException in case of parsing errors
 * @see #loadBeanDefinitions
 * @see #setDocumentReaderClass
 * @see BeanDefinitionDocumentReader#registerBeanDefinitions
 */
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
   BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
   int countBefore = getRegistry().getBeanDefinitionCount();
   documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
   return getRegistry().getBeanDefinitionCount() - countBefore;
}

/**
 * Register each bean definition within the given root {@code <beans/>} element.
 */
protected void doRegisterBeanDefinitions(Element root) {
   // Any nested <beans> elements will cause recursion in this method. In
   // order to propagate and preserve <beans> default-* attributes correctly,
   // keep track of the current (parent) delegate, which may be null. Create
   // the new (child) delegate with a reference to the parent for fallback purposes,
   // then ultimately reset this.delegate back to its original (parent) reference.
   // this behavior emulates a stack of delegates without actually necessitating one.
   BeanDefinitionParserDelegate parent = this.delegate;
   this.delegate = createDelegate(getReaderContext(), root, parent);

   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);
   parseBeanDefinitions(root, this.delegate);
   postProcessXml(root);

   this.delegate = parent;
}

/**
 * Parse the elements at the root level in the document:
 * "import", "alias", "bean".
 * @param root the DOM root element of the document
 */
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)) {
               parseDefaultElement(ele, delegate);
            }
            else {
               delegate.parseCustomElement(ele);
            }
         }
      }
   }
   else {
      delegate.parseCustomElement(root);
   }
}

--------------------------------------------------------------------------------------------------------------------------

AnnotationConfigWebApplicationContext.java

@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) {
   AnnotatedBeanDefinitionReader reader = getAnnotatedBeanDefinitionReader(beanFactory);
   ClassPathBeanDefinitionScanner scanner = getClassPathBeanDefinitionScanner(beanFactory);

   BeanNameGenerator beanNameGenerator = getBeanNameGenerator();
   if (beanNameGenerator != null) {
      reader.setBeanNameGenerator(beanNameGenerator);
      scanner.setBeanNameGenerator(beanNameGenerator);
      beanFactory.registerSingleton(AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR, beanNameGenerator);
   }

   ScopeMetadataResolver scopeMetadataResolver = getScopeMetadataResolver();
   if (scopeMetadataResolver != null) {
      reader.setScopeMetadataResolver(scopeMetadataResolver);
      scanner.setScopeMetadataResolver(scopeMetadataResolver);
   }

   if (!this.annotatedClasses.isEmpty()) {
      if (logger.isInfoEnabled()) {
         logger.info("Registering annotated classes: [" +
               StringUtils.collectionToCommaDelimitedString(this.annotatedClasses) + "]");
      }
      reader.register(this.annotatedClasses.toArray(new Class<?>[this.annotatedClasses.size()]));
   }

   if (!this.basePackages.isEmpty()) {
      if (logger.isInfoEnabled()) {
         logger.info("Scanning base packages: [" +
               StringUtils.collectionToCommaDelimitedString(this.basePackages) + "]");
      }
      scanner.scan(this.basePackages.toArray(new String[this.basePackages.size()]));
   }

   String[] configLocations = getConfigLocations();
   if (configLocations != null) {
      for (String configLocation : configLocations) {
         try {
            Class<?> clazz = getClassLoader().loadClass(configLocation);
            if (logger.isInfoEnabled()) {
               logger.info("Successfully resolved class for [" + configLocation + "]");
            }
            reader.register(clazz);
         }
         catch (ClassNotFoundException ex) {
            if (logger.isDebugEnabled()) {
               logger.debug("Could not load class for config location [" + configLocation +
                     "] - trying package scan. " + ex);
            }
            int count = scanner.scan(configLocation);
            if (logger.isInfoEnabled()) {
               if (count == 0) {
                  logger.info("No annotated classes found for specified class/package [" + configLocation + "]");
               }
               else {
                  logger.info("Found " + count + " annotated classes in package [" + configLocation + "]");
               }
            }
         }
      }
   }
}
//参考大神
http://geeekr.com/read-spring-source-1-how-to-load-bean/