public class UserService {//实现dao层的一个实例对象private UserDAO userDAO=new UserDAOImpl();//userDAO的setter和getterpublic UserDAO getUserDao() {return userDAO;}public void setUserDAO(UserDAO userDAO) {this.userDAO = userDAO;}//添加用户public void add(User user) {if (userDAO == null)System.out.println("erro");else {userDAO.add(user);}}}

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

package com.spring.buildframework;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 {private static Map<String, Object> beans = new HashMap<String, Object>();public ClassPathXMLApplicationContext() {SAXBuilder sb = new SAXBuilder();try {Document doc = sb.build(this.getClass().getClassLoader().getResourceAsStream("beans.xml"));//获取根节点Element root=doc.getRootElement();//将根节点的下的孩子全部放到List中List allList= root.getChildren("bean");for(int i=0;i<allList.size();i++){Element sigElement=(Element)allList.get(i);//获取每个<bean>节点的id和class属性的值String id=sigElement.getAttribute("id").getValue();String clazz=sigElement.getAttribute("class").getValue();System.out.println(id+clazz);//根据获取的类名利用反射得到实例Class<?> demo=Class.forName(clazz);Object obj=demo.newInstance();//将id和类的实例放到beans中beans.put(id, obj);//判断该bean下是否存在property的子节点List propertyChild=sigElement.getChildren("property");for(int j=0;j<propertyChild.size();j++){//获取此bean下name和bean的属性 ，其中bean指的是配置文件中另一个beanElement propertyElement=(Element)propertyChild.get(j);String name=propertyElement.getAttributeValue("name");  //userDAOString bean=propertyElement.getAttributeValue("bean");    //u//拼接该bean（useDAO）的setter方法 setUserDAOString setterMethodName="set"+name.substring(0,1).toUpperCase()+name.substring(1);//调用setter方法是需要注入com.spring.dao.impl.UserDAOImpl类的 对象Object  fieldObj=beans.get(bean);//获取fieldObj对象的类的类型，Class<?> type=fieldObj.getClass().getInterfaces()[0];Method setterMethod=obj.getClass().getMethod(setterMethodName, type);setterMethod.invoke(obj,fieldObj);System.out.println(type);}}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}//提供给外界接口public static Object getBean(String id){return beans.get(id);}}

package com.spring.service;import com.spring.dao.UserDAO;
import com.spring.dao.impl.UserDAOImpl;
import com.spring.model.User;public class UserService {private UserDAO userDAO;public UserDAO getUserDao() {return userDAO;}public void setUserDAO(UserDAO userDAO) {this.userDAO = userDAO;}public void add(User user) {if (userDAO == null)System.out.println("erro");else {userDAO.add(user);}}}

public class UserDAOImpl implements UserDAO {@Overridepublic void add(User user) {// TODO Auto-generated method stubSystem.out.println("user added successful");}}package com.spring.dao;import com.spring.model.User;public interface UserDAO {public void add(User user);
}package com.spring.model;public class User {private String username;private String age;
public String getUsername() {return username;
}
public void setUsername(String username) {this.username = username;
}
public String getAge() {return age;
}
public void setAge(String age) {this.age = age;
}}

public class ClassPathXMLApplicationContextTest {@Testpublic void test() {try {//   Class<?> demo=Class.forName("com.spring.dao.impl.UserDAOImpl");} catch (Exception e) {// TODO: handle exception}//得到转载容器类的实例ClassPathXMLApplicationContext test=new ClassPathXMLApplicationContext();                //从容器中获取userService对象UserService service=(UserService)ClassPathXMLApplicationContext.getBean("userService");User user=new User();                //执行方法service.add(user);fail("Not yet implemented");}}