3.Spring-用反射模拟IoC

1.BeanFactory.java

 package com.jike.spring.chapter03.reflect;

 import java.io.InputStream;
 import java.lang.reflect.Method;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;

 import org.dom4j.Attribute;
 import org.dom4j.Document;
 import org.dom4j.Element;
 import org.dom4j.io.SAXReader;

 public class BeanFactory {

     private Map<String, Object> beanMap = new HashMap<String, Object>();

     /**
      * bean工厂的初始化.
      *
      * @param xml xml配置文件
      */
     public void init(String xml) {
         try {
             //1.创建读取配置文件的reader对象
             SAXReader reader = new SAXReader();

             //2.获取当前线程中的类装载器对象
             ClassLoader classLoader = Thread.currentThread().getContextClassLoader();

             //3.从class目录下获取指定的xml文件
             InputStream ins = classLoader.getResourceAsStream(xml);
             Document doc = reader.read(ins);
             Element root = doc.getRootElement();
             Element foo;

             //4.遍历xml文件当中的Bean实例
             for (Iterator i = root.elementIterator("bean"); i.hasNext();) {
                 foo = (Element) i.next();

                 //5.针对每个一个Bean实例，获取bean的属性id和class
                 Attribute id = foo.attribute("id");
                 Attribute cls = foo.attribute("class");

                 //6.利用Java反射机制，通过class的名称获取Class对象
                 Class bean = Class.forName(cls.getText());
                 //7.获取对应class的信息
                 java.beans.BeanInfo info = java.beans.Introspector.getBeanInfo(bean);
                 //8.获取其属性描述
                 java.beans.PropertyDescriptor pd[] = info.getPropertyDescriptors();

                 //9.创建一个对象，并在接下来的代码中为对象的属性赋值
                 Object obj = bean.newInstance();

                 //10.遍历该bean的property属性
                 for (Iterator ite = foo.elementIterator("property"); ite.hasNext();) {
                     Element foo2 = (Element) ite.next();

                     //11.获取该property的name属性
                     Attribute name = foo2.attribute("name");
                     String value = null;

                     //12.获取该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的反射机制调用对象的某个set方法，并将值设置进去
                     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.将对象放入beanMap中，其中key为id值，value为对象
                 beanMap.put(id.getText(), obj);
             }
         } catch (Exception e) {
             System.out.println(e.toString());
         }
     }

     /**
      * 通过bean的id获取bean的对象.
      *
      * @param beanName
      *            bean的id
      * @return 返回对应对象
      */
     public Object getBean(String beanName) {
         Object obj = beanMap.get(beanName);
         return obj;
     }

     /**
      * 测试方法.
      *
      * @param args
      */
     public static void main(String[] args) {
         BeanFactory factory = new BeanFactory();
         factory.init("conf/config.xml");
         JavaBean javaBean = (JavaBean) factory.getBean("javaBean");
         System.out.println("userName=" + javaBean.getUserName());
         System.out.println("password=" + javaBean.getPassword());
     }
 }