Spring_使用XML配置文件创建对象

<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>

package com.bjsxt.spring;

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

package com.bjsxt.spring;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.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 document = sb.build(ClassPathXmlApplicationContext.class
        .getClassLoader().getResource("beans.xml"));// 获取文件
    Element root = document.getRootElement();// 获取根元素
    List list = root.getChildren();// 获取名字为bean的所有元素(子元素)
    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 obj = Class.forName(clazz).newInstance();
      beans.put(id, obj);
    }
  }

  @Override
  public Object getBean(String name) {
    return beans.get(name);
  }

}

package com.bjsxt.service;

import org.junit.Test;

import com.bjsxt.dao.UserDao;
import com.bjsxt.model.User;
import com.bjsxt.spring.BeanFactory;
import com.bjsxt.spring.ClassPathXmlApplicationContext;

public class UserServiceTest {

  @Test
  public void testAdd() throws Exception {
    BeanFactory factory = new ClassPathXmlApplicationContext();

    UserService service = new UserService();
    UserDao ud = (UserDao) factory.getBean("u");
    service.setUd(ud);
    User user = new User();
    service.add(user);
  }

}