示例
先给出两个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 id="person" class="com.john.aop.Person">
</bean>
<bean id="ChineseFemaleSinger" class="com.john.beanFactory.Singer" abstract="true" >
<property name="country" value="中国"/>
<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 id="carFactory" class="com.john.domain.CarFactory" />
<!--实例工厂方法创建bean-->
<bean id="instanceCar" factory-bean="carFactory" factory-method="createCar">
<constructor-arg ref="brand"/>
</bean>
<bean id="brand" class="com.john.domain.Brand" />
</beans>java示例代码
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);
}
}
}这样我们就会在控制台打印出两个配置文件中所有的Bean.
person
ChineseFemaleSinger
carFactory
instanceCar
brand
Process finished with exit code 0实现
AbstractRefreshableConfigApplicationContext
从类的名字推导出这是一个带刷新功能并且带配置功能的应用上下文。
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;
}
}这个方法很好理解，首先根据传入配置文件路径字符串数组遍历，并且里面调用了resolvePath方法解析占位符。那么我们要想下了，这里只做了解析占位符并且把字符串赋值给configLocations变量，那必然肯定会在什么时候去读取这个路径下的文件并加载bean吧？会不会是在应用上下文调用refresh方法的时候去加载呢？带着思考我们来到了应用上下文的refresh方法。
AbstractApplicationContext
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Tell the subclass to refresh the internal bean factory.
//告诉子类刷新 内部BeanFactory
//https://www.iteye.com/blog/rkdu2-163-com-2003638
//内部会加载bean定义
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
}
}
//得到刷新过的beanFactory
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
//抽象类AbstractRefreshableApplicationContext
//里面会加载bean定义
//todo 加载bean定义
refreshBeanFactory();
//如果beanFactory为null 会报错
return getBeanFactory();
}
//AbstractRefreshableApplicationContext 实现了此方法
//GenericApplicationContext 实现了此方法
protected abstract void refreshBeanFactory() throws BeansException, IllegalStateException;我们看到refreshBeanFactory的第一句注释就提到了Subclasses must implement this method to perform the actual configuration load，意思就是子类必须实现此方法来完成最终的配置加载，那实现此方法的Spring内部默认有两个类，AbstractRefreshableApplicationContext和GenericApplicationContext，这里我们就关心AbstractRefreshableApplicationContext：
AbstractRefreshableApplicationContext
我们要时刻记得上面的AbstractRefreshableConfigApplicationContext类是继承于AbstractRefreshableApplicationContext的，到这里我们给张类关系图以便加深理解：
@Override
protected final void refreshBeanFactory() throws BeansException {
//判断beanFactory 是否为空
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory(); //设置beanFactory = null
}
try {
DefaultListableBeanFactory beanFactory = createBeanFactory();
//加载Bean定义
//todo AbstractXmlApplicationContext 子类实现 放入beandefinitionMap中
loadBeanDefinitions(beanFactory);
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}这里就看到了前篇文章提到一个很重要的方法loadBeanDefinitions，我们再拿出来回顾下加深理解：
protected abstract void loadBeanDefinitions(DefaultListableBeanFactory beanFactory)
throws BeansException, IOException;这里因为我们是采用xml配置的，那么肯定是XmlBeanDefinitionReader无疑，我们再回顾下实现此方法的AbstractXmlApplicationContext：
AbstractXmlApplicationContext
//todo 重载了 AbstractRefreshableApplicationContext
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
//忽略代码。。
loadBeanDefinitions(beanDefinitionReader);
}
//bean工厂的生命周期由 refreshBeanFactory 方法来处理
//这个方法只是 去加载和注册 bean定义
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
//ClassPathXmlApplicationContext
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
String[] configLocations = getConfigLocations();
if (configLocations != null) {
//抽象AbstractBeanDefinitionReader里去加载
reader.loadBeanDefinitions(configLocations);
}
}这里我们终于到了这个configLocations的用武之地，它就传入了XmlBeanDefinitionReader的loadBeanDefinitions方法中。在这里我们也看到了Spring首先会根据configResources加载BeanDefinition，其次才会去根据configLocations配置去加载BeanDefinition。到这里我们可以学到Spring中对面向对象中封装，继承和多态的运用。下篇文章我们继续剖析Spring关于Xml加载Bean定义的点滴。
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