1 package com.bjsxt.spring;2 3 public interface BeanFactory {4     public Object getBean(String name);5 }

 1 package com.bjsxt.spring; 2  3 import java.lang.reflect.Method; 4 import java.util.HashMap; 5 import java.util.List; 6 import java.util.Map; 7  8 import org.jdom.Document; 9 import org.jdom.Element;10 import org.jdom.input.SAXBuilder;11 12 public class ClassPathXmlApplicationContext implements BeanFactory{13     private Map<String, Object> beans = new HashMap<String, Object>();14     15     public ClassPathXmlApplicationContext() throws Exception{16         SAXBuilder sb = new SAXBuilder();17         Document doc = sb.build(this.getClass().getClassLoader().getResourceAsStream("beans.xml"));18         Element root = doc.getRootElement();//获取根元素19         List list = root.getChildren("bean");//取名字为bean的所有元素20         for(int i=0; i<list.size(); i++){21             Element element = (Element) list.get(i);22             String id = element.getAttributeValue("id");23             String clazz = element.getAttributeValue("class");24             System.out.println(id + ":" + clazz);25             Object o = Class.forName(clazz).newInstance();26             beans.put(id, o);27             28             for(Element propertyElement : (List<Element>)element.getChildren("property")){29                 String name = propertyElement.getAttributeValue("name");//userDAO30                 String bean = propertyElement.getAttributeValue("bean");//u31                 Object beanObject = beans.get(bean);//UserDAOImpl instance32                 33                 String methodName = "set" + name.substring(0, 1).toUpperCase() + name.substring(1);34                 System.out.println("method name = " + methodName);35                 36                 Method m = o.getClass().getMethod(methodName, beanObject.getClass().getInterfaces()[0]);37                 m.invoke(o, beanObject);    38             }39         }40     }41 42     public Object getBean(String name) {43         return beans.get(name);44     }45     46 }

1 <beans>2     <bean id="u" class="com.bjsxt.dao.impl.UserDAOImpl"></bean>3     <bean id="userService" class="com.bjsxt.service.UserService">4         <property name="userDAO" bean="u"></property>5     </bean>6 </beans>

1 package com.bjsxt.dao;2 3 import com.bjsxt.model.User;4 5 public interface UserDAO {6     public void save(User u);7 }

 1 package com.bjsxt.dao.impl; 2  3 import com.bjsxt.dao.UserDAO; 4 import com.bjsxt.model.User; 5  6 public class UserDAOImpl implements UserDAO{ 7  8     public void save(User u) { 9         System.out.println("a user saved!");10     }11 12 }

 1 package com.bjsxt.service; 2  3 import org.junit.Test; 4  5 import com.bjsxt.model.User; 6 import com.bjsxt.spring.BeanFactory; 7 import com.bjsxt.spring.ClassPathXmlApplicationContext; 8  9 public class UserServiceTest {10 11     @Test12     public void testAddUser() throws Exception {13         BeanFactory factory = new ClassPathXmlApplicationContext();14         15         UserService service = (UserService)factory.getBean("userService");16         User u = new User();17         service.addUser(u);18     }19 20 }