目錄示例spring-configlication.xml:spring-config-instance-factory.xmljava示例代碼實(shí)現(xiàn)AbstractRefreshableConfigApplicationContextAbstractApplicationContextAbstractRefreshableApplicationContextAbstractXmlApplicationContext示例

先給出兩個(gè)Bean的配置文件:

spring-configlication.xml:

<?xml version='1.0' encoding='UTF-8'?><beans xmlns='http://www.springframework.org/schema/beans' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:context='http://www.springframework.org/schema/context' xmlns:aop='http://www.springframework.org/schema/aop' xsi:schemaLocation='http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd'> <bean class='com.john.aop.Person'> </bean> <bean abstract='true' ><property name='country' value='中國(guó)'/><property name='gender' value='女'/> </bean></beans>spring-config-instance-factory.xml

<?xml version='1.0' encoding='UTF-8'?><beans xmlns='http://www.springframework.org/schema/beans' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:context='http://www.springframework.org/schema/context' xmlns:aop='http://www.springframework.org/schema/aop' xsi:schemaLocation='http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd'> <bean /> <!--實(shí)例工廠方法創(chuàng)建bean--> <bean factory-bean='carFactory' factory-method='createCar'><constructor-arg ref='brand'/> </bean> <bean /></beans>java示例代碼

public class ConfigLocationsDemo { public static void main(String[] args) {ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext();applicationContext.setConfigLocations('spring-configlocation.xml','spring-config-instance-factory.xml');applicationContext.refresh(); String[] beanNames = applicationContext.getBeanDefinitionNames();for (String beanName : beanNames) { System.out.println(beanName);} }}

這樣我們就會(huì)在控制臺(tái)打印出兩個(gè)配置文件中所有的Bean.

personChineseFemaleSingercarFactoryinstanceCarbrandProcess finished with exit code 0實(shí)現(xiàn)AbstractRefreshableConfigApplicationContext

從類(lèi)的名字推導(dǎo)出這是一個(gè)帶刷新功能并且?guī)渲霉δ艿膽?yīng)用上下文。

/** * Set the config locations for this application context. * <p>If not set, the implementation may use a default as appropriate. */ public void setConfigLocations(@Nullable String... locations) {if (locations != null) { this.configLocations = new String[locations.length]; for (int i = 0; i < locations.length; i++) {this.configLocations[i] = resolvePath(locations[i]).trim(); }}else { this.configLocations = null;} }

這個(gè)方法很好理解，首先根據(jù)傳入配置文件路徑字符串?dāng)?shù)組遍歷，并且里面調(diào)用了resolvePath方法解析占位符。那么我們要想下了，這里只做了解析占位符并且把字符串賦值給configLocations變量，那必然肯定會(huì)在什么時(shí)候去讀取這個(gè)路徑下的文件并加載bean吧？會(huì)不會(huì)是在應(yīng)用上下文調(diào)用refresh方法的時(shí)候去加載呢？帶著思考我們來(lái)到了應(yīng)用上下文的refresh方法。

AbstractApplicationContext

@Override public void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) { // Tell the subclass to refresh the internal bean factory. //告訴子類(lèi)刷新 內(nèi)部BeanFactory //https://www.iteye.com/blog/rkdu2-163-com-2003638 //內(nèi)部會(huì)加載bean定義 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); } } /** * Tell the subclass to refresh the internal bean factory. * @return the fresh BeanFactory instance * @see #refreshBeanFactory() * @see #getBeanFactory() */ //得到刷新過(guò)的beanFactory protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {//抽象類(lèi)AbstractRefreshableApplicationContext//里面會(huì)加載bean定義//todo 加載bean定義refreshBeanFactory();//如果beanFactory為null 會(huì)報(bào)錯(cuò)return getBeanFactory(); } /** * Subclasses must implement this method to perform the actual configuration load. * The method is invoked by {@link #refresh()} before any other initialization work. * <p>A subclass will either create a new bean factory and hold a reference to it, * or return a single BeanFactory instance that it holds. In the latter case, it will * usually throw an IllegalStateException if refreshing the context more than once. * @throws BeansException if initialization of the bean factory failed * @throws IllegalStateException if already initialized and multiple refresh * attempts are not supported */ //AbstractRefreshableApplicationContext 實(shí)現(xiàn)了此方法 //GenericApplicationContext 實(shí)現(xiàn)了此方法 protected abstract void refreshBeanFactory() throws BeansException, IllegalStateException;

我們看到refreshBeanFactory的第一句注釋就提到了Subclasses must implement this method to perform the actual configuration load，意思就是子類(lèi)必須實(shí)現(xiàn)此方法來(lái)完成最終的配置加載，那實(shí)現(xiàn)此方法的Spring內(nèi)部默認(rèn)有兩個(gè)類(lèi)，AbstractRefreshableApplicationContext和GenericApplicationContext，這里我們就關(guān)心AbstractRefreshableApplicationContext：

AbstractRefreshableApplicationContext

我們要時(shí)刻記得上面的AbstractRefreshableConfigApplicationContext類(lèi)是繼承于AbstractRefreshableApplicationContext的，到這里我們給張類(lèi)關(guān)系圖以便加深理解：

/** * This implementation performs an actual refresh of this context’s underlying * bean factory, shutting down the previous bean factory (if any) and * initializing a fresh bean factory for the next phase of the context’s lifecycle. */ @Override protected final void refreshBeanFactory() throws BeansException { //判斷beanFactory 是否為空if (hasBeanFactory()) { destroyBeans(); closeBeanFactory(); //設(shè)置beanFactory = null}try { DefaultListableBeanFactory beanFactory = createBeanFactory(); //加載Bean定義 //todo AbstractXmlApplicationContext 子類(lèi)實(shí)現(xiàn) 放入beandefinitionMap中 loadBeanDefinitions(beanFactory);}catch (IOException ex) { throw new ApplicationContextException('I/O error parsing bean definition source for ' + getDisplayName(), ex);} }

這里就看到了前篇文章提到一個(gè)很重要的方法loadBeanDefinitions，我們?cè)倌贸鰜?lái)回顧下加深理解：

/** * Load bean definitions into the given bean factory, typically through * delegating to one or more bean definition readers. * @param beanFactory the bean factory to load bean definitions into * @throws BeansException if parsing of the bean definitions failed * @throws IOException if loading of bean definition files failed * @see org.springframework.beans.factory.support.PropertiesBeanDefinitionReader * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader */ protected abstract void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException;

這里因?yàn)槲覀兪遣捎脁ml配置的，那么肯定是XmlBeanDefinitionReader無(wú)疑，我們?cè)倩仡櫹聦?shí)現(xiàn)此方法的AbstractXmlApplicationContext：

AbstractXmlApplicationContext

/** * Loads the bean definitions via an XmlBeanDefinitionReader. * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader * @see #initBeanDefinitionReader * @see #loadBeanDefinitions */ //todo 重載了 AbstractRefreshableApplicationContext @Override protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {//忽略代碼。。loadBeanDefinitions(beanDefinitionReader); } /** * Load the bean definitions with the given XmlBeanDefinitionReader. * <p>The lifecycle of the bean factory is handled by the {@link #refreshBeanFactory} * method; hence this method is just supposed to load and/or register bean definitions. * @param reader the XmlBeanDefinitionReader to use * @throws BeansException in case of bean registration errors * @throws IOException if the required XML document isn’t found * @see #refreshBeanFactory * @see #getConfigLocations * @see #getResources * @see #getResourcePatternResolver */ //bean工廠的生命周期由 refreshBeanFactory 方法來(lái)處理 //這個(gè)方法只是 去加載和注冊(cè) bean定義 protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {//ClassPathXmlApplicationContextResource[] configResources = getConfigResources();if (configResources != null) { reader.loadBeanDefinitions(configResources);}String[] configLocations = getConfigLocations();if (configLocations != null) { //抽象AbstractBeanDefinitionReader里去加載 reader.loadBeanDefinitions(configLocations);} }

這里我們終于到了這個(gè)configLocations的用武之地，它就傳入了XmlBeanDefinitionReader的loadBeanDefinitions方法中。在這里我們也看到了Spring首先會(huì)根據(jù)configResources加載BeanDefinition，其次才會(huì)去根據(jù)configLocations配置去加載BeanDefinition。到這里我們可以學(xué)到Spring中對(duì)面向?qū)ο笾蟹庋b，繼承和多態(tài)的運(yùn)用。下篇文章我們繼續(xù)剖析Spring關(guān)于Xml加載Bean定義的點(diǎn)滴。

以上就是Spring 加載多個(gè)xml配置文件的原理分析的詳細(xì)內(nèi)容，更多關(guān)于Spring 加載xml配置文件的資料請(qǐng)關(guān)注好吧啦網(wǎng)其它相關(guān)文章！