Spring 之 模拟Spring中的IOC

Sprig 之 模拟Spring IOC

 

       IOC是Spring的核心，其他的我也不多说了，直接进入主题。

1.       创建实体类User.java

package com.zsw.spring.ioc;
 
  
 
public 
 class User {
 
     
 private 
 int id;
 
     
 private 
 String name;
 
     
 private 
 String age;
 
     
 
    
 // ….舍略getter/setter
 
     
 
 }

2.       创建Dao层UserDao.java/UserDaoImpl.java

package com.zsw.spring.ioc;
 
public 
 interface UserDao {
 
     
 public 
 void add();
 
 }
 

 
package com.zsw.spring.ioc;
  
public 
  class UserDaoImpl 
  implements UserDao {
  
     @Override
  
     
  public 
  void add() {      
  
     }
  
 }

 

3.       创建Service层UserService..java

package com.zsw.spring.ioc;
 
public 
 class UserService {
 
     
 private UserDao userDao;
 
     
 public 
 void setUserDao(UserDao userDao) {
 
        
 this.userDao = userDao;
 
     }
 
 }

4.       定义一个BeanFactory接口和Spring的取名一样

 

package com.zsw.spring.ioc;
  
public 
  interface BeanFactory {
  
     
  public Object getBean(
  String name);
  
 }

5.       定义ClassPathXmlApplicationContext 实现BeanFactory接口

这也是和Spring中的取名相同，具体实现如下：

在初始化的时候读取配置文件，根据反射机制实例化相应的对象及注入相关的依赖对象。

package com.zsw.spring.ioc;
 
  
 
import java.lang.reflect.Method;
 
import java.util.HashMap;
 
import java.util.List;
 
import java.util.Map;
 
  
 
import org.jdom.Document;
 
import org.jdom.Element;
 
import org.jdom.input.SAXBuilder;
 
  
 
public 
 class ClassPathXmlApplicationContext 
 implements BeanFactory {
 
  
 
     
 private Map<
 String,Object> beans = 
 new HashMap<
 String, Object>();
 
     
 
     
 public ClassPathXmlApplicationContext() 
 throws 
 Exception{
 
        SAXBuilder sb = 
 new SAXBuilder();
 
        Document doc = sb.build(
 this.getClass().getClassLoader().getResourceAsStream(
 "bean.xml"));
 
        Element root = doc.getRootElement();  
 //获取根元素
 
        List list = (List) root.getChildren(
 "bean"); 
 //获取名字为bean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");          
 
            System.out.println(id + 
 ":" + clazz);
 
            Object o = Class.forName(clazz).newInstance();
 
            beans.put(id, o);
 
            
 
            
 
            
 for(Element propertyElement : (List<Element>)element.getChildren(
 "property")){
 
               
 String name = propertyElement.getAttributeValue(
 "name");
 
               
 String bean = propertyElement.getAttributeValue(
 "bean");
 
               Object beanObject = beans.get(bean);             
 
               
 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);
 
            }
 
        }
 
     }
 
  
 
     @Override
 
     
 public Object getBean(
 String name) {      
 
        
 return beans.get(name);
 
     }
 
 }

6.       配置文件bean.xml如下：

"1.0" encoding=
 "UTF-8"?>
 
 <beans>
 
     <bean id=
 "user" 
 class=
 "com.zsw.spring.ioc.User" />
 
     <bean id=
 "userDao" 
 class=
 "com.zsw.spring.ioc.UserDaoImpl"></bean>
 
     <bean id=
 "userService" 
 class=
 "com.zsw.spring.ioc.UserService">
 
        <property name=
 "userDao" bean=
 "userDao" />
 
     </bean>
 
 </beans>

 

7.       最后编写测试类

package com.zsw.spring.ioc;
  
public 
  class UserServiceTest {
  
     
  public 
  static 
  void main(
  String[] args) 
  throws 
  Exception {
  
        BeanFactory factory = 
  new ClassPathXmlApplicationContext(); 
  
        UserDao service = (UserDao) factory.getBean(
  "userDao");     
  
     }
  
 }