java反射機制（三）---java的反射和代理實現IOC模式 類比spring

IOC（Inverse of Control）可翻譯為“控制反轉”，但大多數人都習慣將它稱為“依賴注入”。在Spring中，通過IOC可以將實作類別、參數資訊等配置在其對應的設定檔中，那麼當需要更改實作類別或參數資訊時，只需要修改設定檔即可，這種方法在上例的基礎上更進一步的降低了類與類之間的耦合。我們還可以對某對象所需要的其它對象進行注入，這種注入都是在設定檔中做的，Spring的IOC的實現原理利用的就是Java的反射機制， Spring還充當了工廠的角色，我們不需要自己建立工廠類。Spring的工廠類會幫我們完成設定檔的讀取、利用反射機制注入對象等工作，我們可以通過bean的名稱擷取對應的對象。 下面讓我們看看如下的類比Spring的bean工廠類： package org.amigo.reflection; 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; /** * bean工廠類.    */ public class BeanFactory {        private Map<String, Object> beanMap = new HashMap<String, Object>();        /**        * bean工廠的初始化.        * @param xml xml設定檔        */        public void init(String xml) {               try {                      //讀取指定的設定檔                      SAXReader reader = new SAXReader();                      ClassLoader classLoader = Thread.currentThread().getContextClassLoader();                      //從class目錄下擷取指定的xml檔案                      InputStream ins = classLoader.getResourceAsStream(xml);                      Document doc = reader.read(ins);                      Element root = doc.getRootElement();                        Element foo;                                           //遍曆bean                      for (Iterator i = root.elementIterator("bean"); i.hasNext();) {                               foo = (Element) i.next();                             //擷取bean的屬性id和class                             Attribute id = foo.attribute("id");                               Attribute cls = foo.attribute("class");                                                         //利用Java反射機制，通過class的名稱擷取Class對象                             Class bean = Class.forName(cls.getText());                                                         //擷取對應class的資訊                             java.beans.BeanInfo info = java.beans.Introspector.getBeanInfo(bean);                             //擷取其屬性描述                             java.beans.PropertyDescriptor pd[] = info.getPropertyDescriptors();                             //設定值的方法                             Method mSet = null;                             //建立一個對象                             Object obj = bean.newInstance();                                                         //遍曆該bean的property屬性                             for (Iterator ite = foo.elementIterator("property"); ite.hasNext();) {                                      Element foo2 = (Element) ite.next();                                    //擷取該property的name屬性                                    Attribute name = foo2.attribute("name");                                    String value = null;                                                                       //擷取該property的子項目value的值                                    for(Iterator ite1 = foo2.elementIterator("value"); ite1.hasNext();) {                                           Element node = (Element) ite1.next();                                           value = node.getText();                                           break;                                    }                                                                       for (int k = 0; k < pd.length; k++) {                                           if (pd[k].getName().equalsIgnoreCase(name.getText())) {                                                  mSet = pd[k].getWriteMethod();                                                  //利用Java的反射極致調用對象的某個set方法，並將值設定進去                                                  mSet.invoke(obj, value);                                           }                                    }                             }                                                         //將對象放入beanMap中，其中key為id值，value為對象                             beanMap.put(id.getText(), obj);                      }               } catch (Exception e) {                      System.out.println(e.toString());               }        }               /**        * 通過bean的id擷取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.