模拟Spring的简单实现

package com.wwj.model; 
 
/** 
 * 实体类 
 * @author wwj 
 * Spring 
 */ 
public class User { 
  private String username; 
  private String password; 
   
  public String getUsername() { 
    return username; 
  } 
  public void setUsername(String username) { 
    this.username = username; 
  } 
  public String getPassword() { 
    return password; 
  } 
  public void setPassword(String password) { 
    this.password = password; 
  } 
} 

package com.wwj.dao; 
 
import com.wwj.model.User; 
 
/** 
 * 面向抽象编程 
 * @author wwj 
 * 优点：增加了灵活性 
 */ 
public interface UserDAO { 
  public void save(User user); 
} 

package com.wwj.dao.impl; 
 
import com.wwj.dao.UserDAO; 
import com.wwj.model.User; 
 
/** 
 * 接口实现类 
 * @author wwj 
 * 
 */ 
public class UserDAOImpl implements UserDAO{ 
 
  @Override 
  public void save(User user) { 
    System.out.println("save user"); 
  } 
   
} 

package com.wwj.service; 
 
import com.wwj.dao.UserDAO; 
import com.wwj.dao.impl.UserDAOImpl; 
import com.wwj.model.User; 
 
/** 
 * 服务类，实现业务逻辑 
 * @author wwj 
 * 
 */ 
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); 
  } 
} 

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

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

package com.wwj.spring; 
 
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{ 
  //定义一个容器，用来存放对象 
  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("beans.xml")); 
    Element root = doc.getRootElement();  //获取根结点 
    List list = root.getChildren("bean");  //取名为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");  //取id值 
      String cla = element.getAttributeValue("class"); //取class值 
      Object o = Class.forName(cla).newInstance(); 
      System.out.println(id); 
      System.out.println(cla); 
      beans.put(id,o); 
       
      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 
         
        //拼凑方法名，实现setUserDAO方法 
        String methodName = "set" + name.substring(0, 1).toUpperCase() + name.substring(1); 
        System.out.println("method name = " + methodName); 
         
        //利用反射机制获取方法对象 
        Method m = o.getClass().getMethod(methodName, beanObject.getClass().getInterfaces()[0]); 
        m.invoke(o, beanObject);  //调用方法 
      } 
       
    } 
     
  } 
 
 
  @Override 
  public Object getBean(String name) { 
    return beans.get("id"); 
  } 
 
} 

package com.wwj.service; 
 
import org.junit.Test; 
 
import com.wwj.model.User; 
import com.wwj.spring.BeanFactory; 
import com.wwj.spring.ClassPathXmlApplicationContext; 
 
/** 
 * 单元测试类 
 * @author wwj 
 * 
 */ 
public class UserServiceTest { 
   
  @Test 
  public void testAdd() throws Exception{ 
    BeanFactory beanFactory = new ClassPathXmlApplicationContext(); 
     
    UserService service =(UserService)beanFactory.getBean("userService"); 
    User u = new User(); 
    service.add(u); 
  } 
   
}