一、ApplicationContext的xml解析工作是通过ClassPathXmlApplicationContext来实现的，其实看过ClassPathXmlApplicationContext的xml源码解析过程的其实都应该知道，xml的解析过程基本上就是用原来的XmlBeanFactory的解析过程完成的。
二、为什么要拿出来单独说一下呢，其目的就是，了解怎么用同样的方式来实现xml解析过程。
三、xml解析过程是通过refresh下的obtainFreshBeanFactory函数实现，所以这里重点讲解obtainFreshBeanFactory的实现过程。
四、xml源码解析：obtainFreshBeanFactory
1）开端
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() { //解析过程 this.refreshBeanFactory(); //这里的beanFactory就是DefaultListableBeanFactory（后续会讲到） ConfigurableListableBeanFactory beanFactory = this.getBeanFactory(); if (this.logger.isDebugEnabled()) { this.logger.debug("Bean factory for " + this.getDisplayName() + ": " + beanFactory); } return beanFactory; }
2）refreshBeanFactory
protected final void refreshBeanFactory() throws BeansException { if (this.hasBeanFactory()) { this.destroyBeans(); this.closeBeanFactory(); } try { //是不是很熟悉，这里也是通过DefaultListableBeanFactory的方式来实现的 DefaultListableBeanFactory beanFactory = this.createBeanFactory(); beanFactory.setSerializationId(this.getId()); //自定义beanFactory，处理循环依赖 //主要作用设置@Autowired和@Qualifier解析器QualifierAnnotationAutowireCandidateResolver this.customizeBeanFactory(beanFactory); //xml解析过程 this.loadBeanDefinitions(beanFactory); Object var2 = this.beanFactoryMonitor; synchronized(this.beanFactoryMonitor) { this.beanFactory = beanFactory; } } catch (IOException var4) { throw new ApplicationContextException("I/O error parsing bean definition source for " + this.getDisplayName(), var4); } }
a、DefaultListableBeanFactory继承关系
这里其实就可以看出ConfigurableListableBeanFactory就是这里的DefaultListableBeanFactory
b、customizeBeanFactory（这里不详细介绍注解的解析过程）
protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) { if (this.allowBeanDefinitionOverriding != null) { beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding.booleanValue()); } if (this.allowCircularReferences != null) { beanFactory.setAllowCircularReferences(this.allowCircularReferences.booleanValue()); } beanFactory.setParameterNameDiscoverer(new LocalVariableTableParameterNameDiscoverer()); beanFactory.setAutowireCandidateResolver(new QualifierAnnotationAutowireCandidateResolver()); }
c、loadBeanDefinitions
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException { //是不是又很熟悉，还是基于XmlBeanDefinitionReader来进行解析了 XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory); beanDefinitionReader.setResourceLoader(this); beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this)); //解析xml this.initBeanDefinitionReader(beanDefinitionReader); this.loadBeanDefinitions(beanDefinitionReader); }
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException { Resource[] configResources = this.getConfigResources(); if (configResources != null) { reader.loadBeanDefinitions(configResources); } //这里是配置方式不一样，我们是通过configLocations进行配置 String[] configLocations = this.getConfigLocations(); if (configLocations != null) { //解析文件 reader.loadBeanDefinitions(configLocations); } }
public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException { Assert.notNull(locations, "Location array must not be null"); int counter = 0; String[] var6 = locations; int var5 = locations.length; for(int var4 = 0; var4 < var5; ++var4) { String location = var6[var4];
//主要目的计数 counter += this.loadBeanDefinitions(location); } return counter; }
public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException { return this.loadBeanDefinitions(location, (Set)null); } public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException { ResourceLoader resourceLoader = this.getResourceLoader(); if (resourceLoader == null) { throw new BeanDefinitionStoreException("Cannot import bean definitions from location [" + location + "]: no ResourceLoader available"); } else { int loadCount; if (!(resourceLoader instanceof ResourcePatternResolver)) { Resource resource = resourceLoader.getResource(location); loadCount = this.loadBeanDefinitions((Resource)resource); if (actualResources != null) { actualResources.add(resource); } if (this.logger.isDebugEnabled()) { this.logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]"); } return loadCount; } else { try { Resource[] resources = ((ResourcePatternResolver)resourceLoader).getResources(location); //包装成Resource，进行解析 loadCount = this.loadBeanDefinitions(resources); if (actualResources != null) { Resource[] var9 = resources; int var8 = resources.length; for(int var7 = 0; var7 < var8; ++var7) { Resource resource = var9[var7]; actualResources.add(resource); } } if (this.logger.isDebugEnabled()) { this.logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]"); } return loadCount; } catch (IOException var10) { throw new BeanDefinitionStoreException("Could not resolve bean definition resource pattern [" + location + "]", var10); } } } }
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException { Assert.notNull(resources, "Resource array must not be null"); int counter = 0; Resource[] var6 = resources; int var5 = resources.length; for(int var4 = 0; var4 < var5; ++var4) { Resource resource = var6[var4]; //单独解析没一个resource counter += this.loadBeanDefinitions((Resource)resource); } return counter; }
d、loadBeanDefinitions（这里是不是很熟悉，这里的解析过程就是XmlBeanFactory里面的xml的核心解析过程）
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException { return this.loadBeanDefinitions(new EncodedResource(resource)); } public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException { Assert.notNull(encodedResource, "EncodedResource must not be null"); if (this.logger.isInfoEnabled()) { this.logger.info("Loading XML bean definitions from " + encodedResource.getResource()); } Set<EncodedResource> currentResources = (Set)this.resourcesCurrentlyBeingLoaded.get(); if (currentResources == null) { currentResources = new HashSet(4); this.resourcesCurrentlyBeingLoaded.set(currentResources); } if (!((Set)currentResources).add(encodedResource)) { throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!"); } else { int var6; try { InputStream inputStream = encodedResource.getResource().getInputStream(); try { InputSource inputSource = new InputSource(inputStream); if (encodedResource.getEncoding() != null) { inputSource.setEncoding(encodedResource.getEncoding()); } var6 = this.doLoadBeanDefinitions(inputSource, encodedResource.getResource()); } finally { inputStream.close(); } } catch (IOException var15) { throw new BeanDefinitionStoreException("IOException parsing XML document from " + encodedResource.getResource(), var15); } finally { ((Set)currentResources).remove(encodedResource); if (((Set)currentResources).isEmpty()) { this.resourcesCurrentlyBeingLoaded.remove(); } } return var6; } }
e、剩下的部分参考：https://www.cnblogs.com/ll409546297/p/9451784.html的源码解析部分第4）点
五、分析一下流程
1）通过ClassPathXmlApplicationContext来进行xml的解析工作
2）首先进行赋值到configLocations的属性上面
3）xml解析过程还是通过XmlBeanDefinitionReader来实现解析
4）xml解析不同的地方：
a、新增解析增加计数
b、返回类型使用接口ConfigurableListableBeanFactory
c、增加string的配置方式，代码编写感觉更好。
d、解析之前和之后，都做了很多其他工作。相比之下拓展了很多其他功能。