xml的配置
<bean id="petStoreService" class="com.jay.spring.PetStoreService"></bean>
读取XML
采用dom4j来读取xml。在工厂类DefaultBeanFactory初始化时就加载xml。代码如下：
SAXReader saxReader = new SAXReader(); Document document = saxReader.read(inputStream); // 获取根节点 Element rootElement = document.getRootElement(); Iterator<Element> iterator = rootElement.elementIterator(); while (iterator.hasNext()) { Element element = iterator.next(); String id = element.attributeValue(ID_ATTRIBUTE); String className = element.attributeValue(CLASS_ATTRIBUTE); BeanDefinition beanDefinition = new BeanDefinition(id, className); beanDefinitionMap.put(id, beanDefinition); }
获取实例
我们将配置文件bean中的信息放在BeanDefinition中，然后将BeanDefinition放在一个全局的map中，key为id。
BeanDefinition 的实体如下：
public class BeanDefinition { private String id; private String beanClassName; public BeanDefinition(String id, String beanClassName) { this.id = id; this.beanClassName = beanClassName; } set和get方法省略 }
获取Bean的代码如下：
@Override public Object getBean(String id) { BeanDefinition bd = getDefinition(id); if (bd == null) { throw new BeanException("BeanDefinition is not exist"); } try { return Class.forName(bd.getBeanClassName()).newInstance(); } catch (Exception e) { throw new BeanException("bean create exception"); } }
源码地址：
https://github.com/XWxiaowei/spring-learn/tree/master/liu-spring-demo
