Simulate spring functions

1. Create User.java with the following content:

package net.model;
/**
 * @项目名：spring2.5
 * @包名：net.model
 * @文件名：User.java
 * @日期：Jun 22, 2011 4:31:22 PM
 * @备注：
 * @作者：apple
 */
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;
}
}

2. Create UserDao.java with the following content:

package net.dao;
import net.model.User;
/**
 * @项目名：spring2.5
 * @包名：net.dao
 * @文件名：UserDao.java
 * @日期：Jun 22, 2011 4:12:42 PM
 * @备注：
 * @作者：apple
 */
public interface UserDao {
public void save(User u);
}

3. Create UserDaoImpl.java with the following content:

package net.dao.impl;
import net.dao.UserDao;
import net.model.User;
/**
 * @项目名：spring2.5
 * @包名：net.dao.impl
 * @文件名：UserDaoImpl.java
 * @日期：Jun 22, 2011 4:13:45 PM
 * @备注：
 * @作者：apple
 */
public class UserDaoImpl implements UserDao {
public void save(User u) {
// TODO Auto-generated method stub
System.out.println("user save...");
}
}

4. Create UserService.java with the following content:

package net.service;
import net.dao.UserDao;
import net.dao.impl.UserDaoImpl;
import net.model.User;
/**
 * @项目名：spring2.5
 * @包名：net.service
 * @文件名：UserService.java
 * @日期：Jun 22, 2011 4:15:47 PM
 * @备注：
 * @作者：apple
 */
public class UserService {
private UserDao userDao ;
public UserDao getUserDao() {
return userDao;
}
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
public void add(User u){
userDao.save(u);
}//这里可以调用任务实现了UserDao接口的save方法了。
}

5. Create BeanFactory.java with the following content:

package net.factory;
/**
 * @项目名：spring2.5
 * @包名：net.factory
 * @文件名：BeanFactory.java
 * @日期：Jun 22, 2011 4:37:08 PM
 * @备注：
 * @作者：apple
 */
public interface BeanFactory {
public Object getBean(String name);
}

6. Create ClassPathXmlApplicationContext.java with the following content:

package net.util;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import net.dao.UserDao;
import net.factory.BeanFactory;
import net.model.User;
import net.service.UserService;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;
/**
 * @项目名：spring2.5
 * @包名：net.util
 * @文件名：ClassPathXmlApplicationContext.java
 * @日期：Jun 22, 2011 4:19:35 PM
 * @备注：
 * @作者：apple
 */
public class ClassPathXmlApplicationContext implements BeanFactory{ 
private Map<String,Object> beans = new HashMap<String, Object>();
    public ClassPathXmlApplicationContext() throws Exception{
    SAXBuilder sb=new SAXBuilder();//创建一个SAXBuilder对象
    Document doc=sb.build(ClassPathXmlApplicationContext.class.getClassLoader().getResourceAsStream("beans.xml")); //构造文档对象
    Element root=doc.getRootElement(); //获取根元素
    List list=root.getChildren("bean");//取名字为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");
          String clazz = element.getAttributeValue("class");
          System.out.println(id + ":" + clazz);
          Object o = Class.forName(clazz).newInstance();
          beans.put(id, o); 
          //* 以下for循环是实现模拟spring自动装配(注入)功能
      //一开始列出此bean的所有property子元素
      for (Element propertyElement : (List<Element>)element.getChildren("property")){
      //获取property子元素中 属性为name的值(也就是需要注入的参数名称)
      String name = propertyElement.getAttributeValue("name");
      //获取property子元素中 属性为bean的值 (需要注入参数的类型),此处的bean值是已经在上面初始化好了的bean的ID了。
      String bean = propertyElement.getAttributeValue("bean");
      //因此此处获取指定ID的bean
      Object beanObject = beans.get(bean);
      
      //组成set方法名称：set + 第一个字母大写 + 其它的字母
      String methodName = "set" + name.substring(0,1).toUpperCase() + name.substring(1);
      System.out.println("methodName = " + methodName);
      //获取bean的set方法，参数(方法名，参数：此参数的类型)
      Method m = o.getClass().getMethod(methodName, beanObject.getClass().getInterfaces()[0]);
      //使用反映机制，执行method方法，从而实现注入功能
      m.invoke(o, beanObject);
      }
       }   
    }
    public Object getBean(String name){
return beans.get(name);
}
    
    public static void main(String[] args){
    BeanFactory factory=null;
try {
factory = new ClassPathXmlApplicationContext();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
UserService service = (UserService)factory.getBean("userService");
User u = new User();
service.add(u);
    }
}

7. Create beans.xml with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<beans>
<bean id="u" class="net.dao.impl.UserDaoImpl">
</bean>
<bean id="userService" class="net.service.UserService">
<property name="userDao" bean="u"/>
</bean>
</beans>