模拟spring框架注入实现原理

这个我是参见了别人的一些东西，不是原创！

定义一些抽象的方法：

package com.huxin.springinject.dao;

public interface Person {
    public void save();
    public void useAxe();
}

package com.huxin.springinject.dao;

public interface Axe {
   public void  chop();

}

实现的一些方法：

package com.huxin.springinject.dao.impl;

import com.huxin.springinject.dao.Axe;
import com.huxin.springinject.dao.Person;

public class Chinese implements Person {
	private Axe axe;
	public Axe getAxe() {
		return axe;
	}

	public void setAxe(Axe axe) {
		this.axe = axe;
	}

	public void save() {
        System.out.println("保存人的方法");
	}
	public void useAxe(){
		axe.chop();
	}
}

package com.huxin.springinject.dao.impl;

import com.huxin.springinject.dao.Axe;

public class StoneAxe implements Axe {

	@Override
	public void chop() {
	   System.out.println("铁斧头砍柴真慢");

	}

}

这里是关键spring框架模拟的实现的一些原理！！！

package junit.test;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.beanutils.ConvertUtils;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.XPath;
import org.dom4j.io.SAXReader;
public class ApplicationContext {
     List<BeanInformation> beansInformation = new ArrayList<BeanInformation>();
     Map<String,Object> singleton = new HashMap<String,Object>();

     public ApplicationContext(){};
     public ApplicationContext(String filename){
    	 readXml(filename);
    	 initBean();
    	 this.injectObject();
     }
     public void readXml(String filename){
    	 SAXReader saxReader = new SAXReader();
    	 Document document = null;
    	 try{
        	 //使用反射机制,通过文件名加载文件路径
    		 URL xmlPath = this.getClass().getClassLoader().getResource(filename);

    		 //通过文件路径获得这个文件的document对象
    		 document = saxReader.read(xmlPath);

    		 Map<String,String> nsMap = new HashMap<String,String>();
 	         nsMap.put("ns","http://www.springframework.org/schema/beans");//加入命名空间

 	         XPath xsub = document.createXPath("//ns:beans/ns:bean");//创建beans/bean查询路径
 	         xsub.setNamespaceURIs(nsMap);//设置命名空间

    		 //获得所有路径下的节点
    		 List<Element> beans = xsub.selectNodes(document);//获取文档下所有bean节点
    		 for(Element element : beans){
    			 System.out.println(element.attributeValue("id"));
    			 System.out.println(element.attributeValue("class"));

    			 BeanInformation beanInformation = new BeanInformation();
    			 beanInformation.setId(element.attributeValue("id"));
    			 beanInformation.setName(element.attributeValue("class"));

    			 XPath xref = element.createXPath("ns:property");//创建properties查询路径
    			 xref.setNamespaceURIs(nsMap);//设置命名空间

    			 List<Element> propertys = xref.selectNodes(element);
    			 for(Element property : propertys){
    				 PropertyInformation propertyInformation = new PropertyInformation();
    				 propertyInformation.setName(property.attributeValue("name"));
    				 propertyInformation.setRef(property.attributeValue("ref"));
    				 propertyInformation.setValue(property.attributeValue("value"));
    				 beanInformation.getPropertyInformation().add(propertyInformation);
    			 }
    			 beansInformation.add(beanInformation);
    		 }
         } catch(Exception e){
        	 e.printStackTrace();
         }
     }

     public void initBean(){
    	 for(BeanInformation beanInformation: beansInformation){
    		 if(beanInformation.getName()!=null && !"".equals(beanInformation.getName())){
    			 //通过反射机制，根据名字初始化这个类
    			try {
					singleton.put(beanInformation.getId(), Class.forName(beanInformation.getName()).newInstance());
				} catch (Exception e) {
					e.printStackTrace();
				}
    		 }
    	 }
     }

     /**
 	 *    关于注入的实现
 	 */
 	private void injectObject() {
 		for(BeanInformation beanInformation : beansInformation){
 			Object bean = singleton.get(beanInformation.getId());
 			if(bean!=null){
 				try {
 					PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();
 					for(PropertyInformation propertyInformation : beanInformation.getPropertyInformation()){
 						for(PropertyDescriptor properdesc : ps){
 							if(propertyInformation.getName().equals(properdesc.getName())){
 								Method setter = properdesc.getWriteMethod();//获取属性的setter方法 ,private
 								if(setter!=null){
 									Object value = null;
 									if(propertyInformation.getRef()!=null && !"".equals(propertyInformation.getRef().trim())){
 										value = singleton.get(propertyInformation.getRef());
 									}else{
 										value = ConvertUtils.convert(propertyInformation.getValue(), properdesc.getPropertyType());
 									}
 									setter.setAccessible(true);
 									setter.invoke(bean, value);//把引用对象注入到属性
 								}
 								break;
 							}
 						}
 					}
 				} catch (Exception e) {
 				}
 			}
 		}
 	}

     public Object getBean(String id){
		 return this.singleton.get(id);
     }
}

package junit.test;

import java.util.HashSet;
import java.util.Set;

public class BeanInformation {
    private String id;
    private String name;
    private Set<PropertyInformation> propertyInformation = new HashSet<PropertyInformation>();
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Set<PropertyInformation> getPropertyInformation() {
		return propertyInformation;
	}
	public void setPropertyInformation(Set<PropertyInformation> propertyInformation) {
		this.propertyInformation = propertyInformation;
	}
}

package junit.test;

public class PropertyInformation {
    private String name;
    private String ref;
    private String value;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getRef() {
		return ref;
	}
	public void setRef(String ref) {
		this.ref = ref;
	}
	public String getValue() {
		return value;
	}
	public void setValue(String value) {
		this.value = value;
	}
}

测试类：

package junit.test;

import com.huxin.springinject.dao.Person;

public class Test {
	public static void main(String[] args) {
		ApplicationContext ac = new ApplicationContext("applicationContext.xml");
		Person person = (Person)ac.getBean("chinese");
		person.save();
		person.useAxe();
	}
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-3.0.xsd">

      <bean id="chinese"  class="com.huxin.springinject.dao.impl.Chinese">
         <property name="axe" ref="stoneAxe"/>
      </bean>
      <bean id="stoneAxe" class="com.huxin.springinject.dao.impl.StoneAxe"/>
</beans>

补充说明： 需要导入dom4j相应的辅助包和junit辅助包！