接下來我們自己來創建一個Spring的Bean工廠類來講述SpringIoC容器的原理
public class BeanFactory {
private Map<String, Object> beanMap = new HashMap<String, Object>();
/**
* bean工廠的初始化.
*
* @param xml xml配置文件
*/
public void init(String xml) {
try {
//1.創建讀取配置文件的reader對象
SAXReader reader = new SAXReader();
//2.獲取當前線程中的類裝載器對象
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
//3.從class目錄下獲取指定的xml文件
InputStream ins = classLoader.getResourceAsStream(xml);
Document doc = reader.read(ins);
Element root = doc.getRootElement();
Element foo;
//4.遍歷xml文件當中的Bean實例
for (Iterator i = root.elementIterator("bean"); i.hasNext();) {
foo = (Element) i.next();
//5.針對每個一個Bean實例,獲取bean的屬性id和class
Attribute id = foo.attribute("id");
Attribute cls = foo.attribute("class");
//6.利用Java反射機制,通過class的名稱獲取Class對象
Class bean = Class.forName(cls.getText());
//7.獲取對應class的信息
java.beans.BeanInfo info = java.beans.Introspector.getBeanInfo(bean);
//8.獲取其屬性描述
java.beans.PropertyDescriptor pd[] = info.getPropertyDescriptors();
//9.創建一個對象,並在接下來的代碼中爲對象的屬性賦值
Object obj = bean.newInstance();
//10.遍歷該bean的property屬性
for (Iterator ite = foo.elementIterator("property"); ite.hasNext();) {
Element foo2 = (Element) ite.next();
//11.獲取該property的name屬性
Attribute name = foo2.attribute("name");
String value = null;
//12.獲取該property的子元素value的值
for (Iterator ite1 = foo2.elementIterator("value"); ite1.hasNext();)
{
Element node = (Element) ite1.next();
value = node.getText();
break;
}
//13.利用Java的反射機制調用對象的某個set方法,並將值設置進去
for (int k = 0; k < pd.length; k++) {
if (pd[k].getName().equalsIgnoreCase(name.getText()))
{
Method mSet = null;
mSet = pd[k].getWriteMethod();
mSet.invoke(obj, value);
}
}
}
//14.將對象放入beanMap中,其中key爲id值,value爲對象
beanMap.put(id.getText(), obj);
}
} catch (Exception e) {
System.out.println(e.toString());
}
}
/**
* 通過bean的id獲取bean的對象.
*
* @param beanName
* bean的id
* @return 返回對應對象
*/
public Object getBean(String beanName) {
Object obj = beanMap.get(beanName);
return obj;
}
/**
* 測試方法.
*
* @param args
*/
public static void main(String[] args) {
BeanFactory factory = new BeanFactory();
factory.init("src/conf/config.xml");
JavaBean javaBean = (JavaBean) factory.getBean("javaBean");
System.out.println("userName=" + javaBean.getUserName());
System.out.println("password=" + javaBean.getPassword());
}
}