Spring2.5.6源代码分析（一）：IOC容器

1. BeanFactory是最顶层的类，从它下手最合适不过。

 

package org.springframework.beans.factory;

import org.springframework.beans.BeansException;

public interface BeanFactory {

     //假如有个bean名字叫myJndiObject是个FactoryBean，用&myJndiObject返回factory, 
     //不然返回factory的实例     
     String FACTORY_BEAN_PREFIX = "&";    

    //根据名字返回bean
    Object getBean(String name) throws BeansException;

    //返回的bean要符合类的类型
    Object getBean(String name, Class requiredType) throws BeansException;

    //带构造函数参数返回bean
    Object getBean(String name, Object[] args) throws BeansException;

    //是否含有某个bean
    boolean containsBean(String name);

    //某个bean是不是单例
    boolean isSingleton(String name) throws NoSuchBeanDefinitionException;

    //某个bean是不是原型，就是有多个实例
    boolean isPrototype(String name) throws NoSuchBeanDefinitionException;

    //检查bean是否是某个类的类型
    boolean isTypeMatch(String name, Class targetType) throws NoSuchBeanDefinitionException;

    //返回某个bean的类的类型
    Class getType(String name) throws NoSuchBeanDefinitionException;

    //得到bean的别名
    String[] getAliases(String name);

}

 

2. FileSystemXmlApplicationContext

从本地读取配置

	public FileSystemXmlApplicationContext(String[] configLocations,
			boolean refresh, ApplicationContext parent) throws BeansException {
		// 交给父类
		super(parent);

		// 调用爷爷类AbstractRefreshableConfigApplicationContext的方法,
		// 父类AbstractXmlApplicationContext里是一些beanFactory的reader方法,
		// 用ApplicationContext直接进爷爷类
		setConfigLocations(configLocations);

		if (refresh) {

			// AbstractApplicationContext的刷新方法是重头戏，里面调用N个方法
			refresh();
		}
	}

 

3. AbstractRefreshableConfigApplicationContext

这个类没多大用，主要把配置文件的路径赋给自身的configLocations字段

	public void setConfigLocations(String[] locations) {
		if (locations != null) {

			// 断言没有null值，否则报所带msg的异常，这个断言我也可以用用
			Assert.noNullElements(locations,
					"Config locations must not be null");

			this.configLocations = new String[locations.length];
			for (int i = 0; i < locations.length; i++) {

				// 路径如果是${...}这样的，就需要处理成系统路径
				this.configLocations[i] = resolvePath(locations[i]).trim();
			}
		} else {
			this.configLocations = null;
		}
	}

 

4. AbstractApplicationContext

	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			//记录启动时间，active标识变为true，输出个日志到控制台
                        prepareRefresh();

			// 在这一步里，所有的xml信息都设置到beandefinition中了
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// Prepare the bean factory for use in this context.
			prepareBeanFactory(beanFactory);

			try {
				// Allows post-processing of the bean factory in context subclasses.
				postProcessBeanFactory(beanFactory);

				// Invoke factory processors registered as beans in the context.
				invokeBeanFactoryPostProcessors(beanFactory);

				// Register bean processors that intercept bean creation.
				registerBeanPostProcessors(beanFactory);

				// 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 all remaining (non-lazy-init) singletons.
				finishBeanFactoryInitialization(beanFactory);

				// Last step: publish corresponding event.
				finishRefresh();
			}

			catch (BeansException ex) {
				// Destroy already created singletons to avoid dangling resources.
				beanFactory.destroySingletons();

				// Reset 'active' flag.
				cancelRefresh(ex);

				// Propagate exception to caller.
				throw ex;
			}
		}
	}

 

4.开始读文档里的Element子节点

    org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader

public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
		this.readerContext = readerContext;

		logger.debug("Loading bean definitions");
		Element root = doc.getDocumentElement();
                
                //设置default值
		BeanDefinitionParserDelegate delegate = createHelper(readerContext, root);
                
                //对预定义的节点做预处理，暂时为空方法 
		preProcessXml(root);
		parseBeanDefinitions(root, delegate);
		postProcessXml(root);
	}

 

 

5. 文档里面的节点设置成类的字段

    org.springframework.beans.factory.xml.BeanDefinitionParserDelegate一个一个解析文档中的节点，属性

	public void initDefaults(Element root) {
		DocumentDefaultsDefinition defaults = new DocumentDefaultsDefinition();
		defaults.setLazyInit(root.getAttribute(DEFAULT_LAZY_INIT_ATTRIBUTE));
		defaults.setMerge(root.getAttribute(DEFAULT_MERGE_ATTRIBUTE));
		defaults.setAutowire(root.getAttribute(DEFAULT_AUTOWIRE_ATTRIBUTE));
		defaults.setDependencyCheck(root.getAttribute(DEFAULT_DEPENDENCY_CHECK_ATTRIBUTE));
		if (root.hasAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE)) {
			defaults.setAutowireCandidates(root.getAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE));
		}
		if (root.hasAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE)) {
			defaults.setInitMethod(root.getAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE));
		}
		if (root.hasAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE)) {
			defaults.setDestroyMethod(root.getAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE));
		}
		defaults.setSource(this.readerContext.extractSource(root));

		this.defaults = defaults;
		this.readerContext.fireDefaultsRegistered(defaults);
	}

 

6. 一开始初始化所有单例的bean

    org.springframework.beans.BeanUtils

	public static Object instantiateClass(Constructor ctor, Object[] args) throws BeanInstantiationException {
		Assert.notNull(ctor, "Constructor must not be null");
		try {
			ReflectionUtils.makeAccessible(ctor);
                        
                        //在这一行真正实例化
                        return ctor.newInstance(args);
		}
		catch (InstantiationException ex) {
			throw new BeanInstantiationException(ctor.getDeclaringClass(),
					"Is it an abstract class?", ex);
		}
		catch (IllegalAccessException ex) {
			throw new BeanInstantiationException(ctor.getDeclaringClass(),
					"Has the class definition changed? Is the constructor accessible?", ex);
		}
		catch (IllegalArgumentException ex) {
			throw new BeanInstantiationException(ctor.getDeclaringClass(),
					"Illegal arguments for constructor", ex);
		}
		catch (InvocationTargetException ex) {
			throw new BeanInstantiationException(ctor.getDeclaringClass(),
					"Constructor threw exception", ex.getTargetException());
		}
	}

 

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