public class Main {
     public static void main(String[] args) {
          /******** 一般写法，Main类与Chinese类和American类之间的强耦合 ***********/
          // Chinese和American，当类和方法修改时，此处的类和方法也需要修改
          Chinese chinese = new Chinese();
          chinese.sayHelloWorld("张三");

          American american = new American();
          american.sayHelloWorld("Jack");
     }
}

/******************** 一般方法 ***************************/

interface Human {
     public void sayHelloWorld(String name);
}


class Chinese implements Human {
     public void sayHelloWorld(String name) {
          String helloWorld = "你好，" + name;
          System.out.println(helloWorld);
     }
}

class American implements Human {
     public void sayHelloWorld(String name) {
          String helloWorld = "Hello，" + name;
          System.out.println(helloWorld);
     }
}

public class Main {
     public static void main(String[] args) {
          /******** 工厂方法， Main类与类Chinese和American不再耦合，仅仅和其接口Human耦合 ***********/
          // 修改时还需要修改在Main类中修改这些字符串
          // Chinese和American，当类和方法修改时，只有方法需要修改
          HumanFactory humanFactory = new HumanFactory();
          Human human1 = humanFactory.getHuman("chinese");
          human1.sayHelloWorld("张三");

          Human human2 = humanFactory.getHuman("american");
          human2.sayHelloWorld("Jack");
     }
}


/******************** 工厂方法 ***************************/
interface Human {
     public void sayHelloWorld(String name);
}

class HumanFactory {
     public Human getHuman(String type) {
          if ("chinese".equals(type)) {
               return new Chinese();
          } else {
               return new American();
          }
     }
}

public class Main {
     public static void main(String[] args) {
          /******************** IOC控制反转和依赖注入 ***************************/
          // 利用容器，通过xml文件直接注入属性值，在Main类中只添加需要的
          // Chinese和American，当类和方法修改时，代码完全不用修改，只需要修改xml文件即可，彻底实现了解耦
          BeanFactory beanFactory = new BeanFactory();
          beanFactory.init("/config.xml");
          UserBean userBean = (UserBean) beanFactory.getBean("userBean");
          System.out.println("userName=" + userBean.getUserName());
          System.out.println("password=" + userBean.getPassword());
     }
}


/******************** IOC控制反转和依赖注入 ***************************/
// 下面是Spring的IOC实现：Bean工厂
class BeanFactory {
     private Map<String, Object> beanMap = new HashMap<String, Object>();

     public void init(String fileName) {
          try {
               // 读取指定的配置文件
               SAXReader reader = new SAXReader();
               // System.out.println(xmlpath);
               String realPathString = new File("").getCanonicalPath();
               Document document = reader.read(new File(realPathString + "/src/com/devin/") + fileName);
               Element root = document.getRootElement();
               Element foo;
               // 遍历bean
               for (Iterator i = root.elementIterator("bean"); i.hasNext();) {
                    foo = (Element) i.next();
                    // 获取bean的属性id和class
                    Attribute id = foo.attribute("id");
                    Attribute cls = foo.attribute("class");
                    // 利用Java反射机制，通过class的名称获取Class对象
                    Class bean = Class.forName(cls.getText());
                    // 获取对应class的信息
                    java.beans.BeanInfo info = java.beans.Introspector.getBeanInfo(bean);
                    // 获取其属性描述
                    java.beans.PropertyDescriptor pd[] = info.getPropertyDescriptors();
                    // 设置值的方法
                    Method mSet = null;
                    // 创建一个对象
                    Object obj = bean.newInstance();
                    // 遍历该bean的property属性
                    for (Iterator ite = foo.elementIterator("property"); ite.hasNext();) {
                         Element foo2 = (Element) ite.next();
                         // 获取该property的name属性
                         Attribute name = foo2.attribute("name");
                         String value = null;
                         // 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;
                         }
                         for (int k = 0; k < pd.length; k++) {
                              if (pd[k].getName().equalsIgnoreCase(name.getText())) {
                                   mSet = pd[k].getWriteMethod();
                                   mSet.invoke(obj, value);
                              }
                         }
                    }

                    // 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.
     public Object getBean(String beanName) {
          Object obj = beanMap.get(beanName);
          return obj;
     }
}


UserBean.java

public class UserBean {
     private String userName;
     private String password;

     public String getPassword() {
          return password;
     }

     public String getUserName() {
          return userName;
     }

     public void setUserName(String userName) {
          this.userName = userName;
     }

     public void setPassword(String password) {
          this.password = password;
     }
}

config.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans>
     <bean id="userBean" class="com.devin.UserBean">
          <property name="userName">
               <value>张三</value>
          </property>
          <property name="password">
               <value>Jack</value>
          </property>
     </bean>
</beans>