模拟Spring的 IOC 和 DI

模拟Spring的 IOC 和 DI
1.BeanFactory 接口

public interface BeanFactory {
	public Object getBean(String id);
}

2.ClassPathXmlApplicationContex实现类

public class ClassPathXmlApplicationContext implements BeanFactory {
	private Map<String , Object> beans = new HashMap<String, Object>();
	
	/** 
	 * 模拟控制反转(IOC)+依赖注入(DI)
	 * IOC Inverse of Control 
	 * DI Dependency Injection
	 */
	public ClassPathXmlApplicationContext() throws Exception {
		SAXBuilder sb=new SAXBuilder();
	    
	    Document doc=sb.build(this.getClass().getClassLoader().getResourceAsStream("beans.xml")); //构造文档对象
	    Element root=doc.getRootElement(); //获取根元素HD
	    List list=root.getChildren("bean");//取名字为disk的所有元素
	    for(int i=0;i<list.size();i++){
	       Element element=(Element)list.get(i);
	       String id=element.getAttributeValue("id");
	       String clazz=element.getAttributeValue("class");
	       Object o = Class.forName(clazz).newInstance();
	       System.out.println(id);
	       System.out.println(clazz);
	       beans.put(id, o);
	       
	       for(Element propertyElement : (List<Element>)element.getChildren("property")) {
	    	   String name = propertyElement.getAttributeValue("name"); //userDAO
	    	   String bean = propertyElement.getAttributeValue("bean"); //u
	    	   Object beanObject = beans.get(bean);//UserDAOImpl instance
	    	   
	    	   String methodName = "set" + name.substring(0, 1).toUpperCase() + name.substring(1);
	    	   System.out.println("method name = " + methodName);
	    	   
	    	   Method m = o.getClass().getMethod(methodName, beanObject.getClass().getInterfaces()[0]);
	    	   m.invoke(o, beanObject);
	       } 
	    }  
	}

	public Object getBean(String id) {
		return beans.get(id);
	}
}

3.applicationContext-beans.xml配置文件

<beans>
	<bean id="u" class="com.bjsxt.dao.impl.UserDAOImpl" />
	<bean id="userService" class="com.bjsxt.service.UserService" >
		<property name="userDAO" bean="u"/>
	</bean>
</beans>

4.UserDAO接口和UserDAOImpl实现类

public interface UserDAO {
	public void save(User user);
}

public class UserDAOImpl implements UserDAO {
	public void save(User user) {
		//Hibernate
		//JDBC
		//XML
		//NetWork
		System.out.println("user saved!");
	}
}

5.UserService接口和实现类UserServiceImpl

public interface UserService {
	public void add(User user);
}

public class UserServiceImpl implements UserService{
     	private UserDAO userDAO;  
	public void add(User user) {
		userDAO.save(user);
	}
	public UserDAO getUserDAO() {
		return userDAO;
	}
	public void setUserDAO(UserDAO userDAO) {
		this.userDAO = userDAO;
	}
}

6.测试类

import com.momo.spring.BeanFactory;
import com.momo.spring.ClassPathXmlApplicationContext;

public class IOCTest {
	@Test
	public void testAdd() throws Exception {
		BeanFactory applicationContext = new ClassPathXmlApplicationContext();
		UserService service = (UserService)applicationContext.getBean("userService");
		User u = new User();
		u.setUsername("zhangsan");
		u.setPassword("zhangsan");
		service.add(u);
	}
}





import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class IOCTest {
	@Test
	public void testAdd() throws Exception {
		ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");//BeanFactory也可以
		UserService service = (UserService)ctx.getBean("userService");
		User u = new User();
		u.setUsername("zhangsan");
		u.setPassword("zhangsan");
		service.add(u);
	}
}