Spring_使用XML配置文件实现依赖注入

<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.lang.reflect.Method;
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>();

  @SuppressWarnings("rawtypes")
  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");// u
      String clazz = element.getAttributeValue("class");// UserDaoImpl
      Object obj = Class.forName(clazz).newInstance();// 生成Class实例UserDaoImpl.class
      System.out.println(id);
      System.out.println(clazz);
      beans.put(id, obj);// 添加至map集合

      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);// setUserDao(set,U,serDao)
        System.out.println("method name = " + methodName);

        Method m = obj.getClass().getMethod(methodName,
            beanObject.getClass().getInterfaces()[0]);
        m.invoke(obj, beanObject);
      }
    }
  }

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

}

package com.bjsxt.service;

import com.bjsxt.dao.UserDao;
import com.bjsxt.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) {
    this.userDao.save(user);
  }
}

package com.bjsxt.service;

import org.junit.Test;

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 = (UserService) factory.getBean("userService");
    
    User user = new User();
    service.add(user);
  }
}