在工作中見得非常多的容器使用是：

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:util="http://www.springframework.org/schema/util"
	xmlns:jee="http://www.springframework.org/schema/jee" xmlns:aop="http://www.springframework.org/schema/aop"
	xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
	xmlns:p="http://www.springframework.org/schema/p" xmlns:cache="http://www.springframework.org/schema/cache"
	xmlns:task="http://www.springframework.org/schema/task"
	xsi:schemaLocation="
	http://www.springframework.org/schema/task 
	http://www.springframework.org/schema/task/spring-task-4.1.xsd
    http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop-4.1.xsd
    http://www.springframework.org/schema/tx
    http://www.springframework.org/schema/tx/spring-tx-4.1.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-4.1.xsd
    http://www.springframework.org/schema/util 
    http://www.springframework.org/schema/util/spring-util-4.1.xsd
    http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache-4.1.xsd">
    <bean id="adapConsumer" class="com.ad.jms.AdapConsumer">
	      <property name="queueChannel" ref="inputFromKafkaAdap"></property>
    </bean>
</beans>

final ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
AdapConsumer adConsumer = app.getBean("adapConsumer", AdapConsumer.class);

其底層實現原理是怎樣的？根據《Spring源碼深度解析》以另外一個容器BeanFactory來解析源碼實現。

一、可以發現BeanFactory是通過XmlBeanFactory創建的，而XmlBeanFactory繼承了DefaultListableBeanFactory，主要增加了XMLBeanDefinitionReader，接下來先認識一下這兩個類。

1.1 DefaultListableBeanFactory

其中各個類的作用

1.2 XMLBeanDefinitionReader

完成了對配置文件進行封裝後配置文件的讀取工作。

二、我們根據BeanFactory bf = new XmlBeanFactory（new ClassPathResource（"beanFactoryTest.xml"））來分析建立過程

2.1 new ClassPathResource（"beanFactoryTest.xml"）

這是通過ClassPathResource構造函數來構造一個ReSource，然後交給XmlBeanFactory的構造函數。那麽ClassPathResource怎麽處理的？

ReSource底層實現：

2.2 new XmlBeanFactory（new ClassPathResource（"beanFactoryTest.xml"））

public class XmlBeanFactory extends DefaultListableBeanFactory {

   private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);

   public XmlBeanFactory(Resource resource) throws BeansException {
      this(resource, null);
   }

   public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
      super(parentBeanFactory);
      this.reader.loadBeanDefinitions(resource);
      
   }
}
//最後一句代碼主要完成下面三個功能

可以看到有XMLBeanDefinitionReader對象（完成了對配置文件進行封裝後配置文件的讀取工作），就是加載bean，在代碼中一層一層往下看：

public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
   return loadBeanDefinitions(new EncodedResource(resource));
}

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<>(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();
      }
   }
}

上面這段代碼真正進入了數據的準備階段執行下面正式進入核心部分：

doLoadBeanDefinitions(inputSource, encodedResource.getResource())

doLoadBeanDefinitions之所以很核心，因為做了三件重要的事情：

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);
   }
}
protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
   return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
         getValidationModeForResource(resource), isNamespaceAware());
}
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;
}

接下來將這三件事情逐個分析：

2.2.1 獲取xml文件的驗證模式

DTD和XSD的區別：

驗證模式的讀取：

protected int getValidationModeForResource(Resource resource) {
   int validationModeToUse = getValidationMode();
   if (validationModeToUse != VALIDATION_AUTO) {
      return validationModeToUse;
   }
   int detectedMode = detectValidationMode(resource);
   if (detectedMode != VALIDATION_AUTO) {
      return detectedMode;
   }
   // Hmm, we didn't get a clear indication... Let's assume XSD,
   // since apparently no DTD declaration has been found up until
   // detection stopped (before finding the document's root tag).
   return VALIDATION_XSD;
}

2.2.2 讀取document

protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
   return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
         getValidationModeForResource(resource), isNamespaceAware());
}

package org.springframework.beans.factory.xml;

import org.w3c.dom.Document;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;

public interface DocumentLoader {

   Document loadDocument(
         InputSource inputSource, EntityResolver entityResolver,
         ErrorHandler errorHandler, int validationMode, boolean namespaceAware)
         throws Exception;

}

2.2.3 根據返回的document註冊bean信息

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);
   }
}

registerBeanDefinitions方法：

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;
}

解析並註冊BeanDefinition

spring源碼--容器的基本實現