Spring学习笔记_模拟Spring

一,分层

UserService层：业务逻辑层      UserDAO:仅仅和数据库打交道、

二,xml文件的读取

<!--test.xml--!>

<?xml version="1.0" encoding="UTF-8"?>
<HD>
  <disk name="C">
    <capacity>8G</capacity>
    <directories>200</directories>
    <files>1580</files>
  </disk>

  <disk name="D">
    <capacity>10G</capacity>
    <directories>500</directories>
    <files>3000</files>
  </disk>
</HD> 

 

 

//sample.java

import java.util.*;
import org.jdom.*;
import org.jdom.input.SAXBuilder;
public class Sample {
  public static void main(String[] args) throws Exception{ 
    SAXBuilder sb=new SAXBuilder();
    
    Document doc=sb.build(Sample.class.getClassLoader().getResourceAsStream("test.xml")); //构造文档对象
    Element root=doc.getRootElement(); //获取根元素HD
    List list=root.getChildren("disk");//取名字为disk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);
       System.out.println(clazz);*/
       
       String name=element.getAttributeValue("name");
       String capacity=element.getChildText("capacity");//取disk子元素capacity的内容
       String directories=element.getChildText("directories");
       String files=element.getChildText("files");
       System.out.println("磁盘信息:");
       System.out.println("分区盘符:"+name);
       System.out.println("分区容量:"+capacity);
       System.out.println("目录数:"+directories);
       System.out.println("文件数:"+files);
       System.out.println("-----------------------------------");
       
    }  
  }
} 

 三,xml中bean的读取

public class ClassPathXmlApplicationContext implements BeanFactory {
    private Map<String, Object> beans=new HashMap<String, Object>();
    
    public ClassPathXmlApplicationContext() throws Exception{
        SAXBuilder sBuilder=new SAXBuilder();
        
        Document document=sBuilder.build(this.getClass().getClassLoader().getResourceAsStream("beans.xml"));
        Element root=document.getRootElement();
        List list=root.getChildren("bean");
        for(int i=0;i<list.size();i++){
            Element element=(Element)list.get(i);
            String id=element.getAttributeValue("id");
            String clazz=element.getAttributeValue("class");
            
            Object o=Class.forName(clazz).newInstance();
            System.out.println(id);
            System.out.println(clazz);
            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
                   
                   String methodName = "set" + name.substring(0, 1).toUpperCase() + name.substring(1);
                   System.out.println("method name = " + methodName);
                   //反射机制
                   Method m = o.getClass().getMethod(methodName, beanObject.getClass().getInterfaces()[0]);
                   m.invoke(o, beanObject);
               }
          
        }
    }
    public Object getBean(String id){
        return beans.get(id);
        
    }
}

四,什么是IOC(DI)

IOC:控制反转，

DI:依赖注入

1，把自己new的东西改为容器提供

　　初始化具体值。

　　装配

2，好处：灵活装配