java模拟spring实现依赖注入

先发下骚扰，进了这间公司，感觉是废了，连一个明确的任务都没有，一家小公司实习。。闲得蛋疼，空闲只好自己找点东西给自己充下电，回补下自己的java基础.

不说了..

还是转入主题吧..

一直以来都只是想学如何用一个东西，学了spring、struts、hibernate框架，也都只是会用简单的运用，完全不怎么理解它里面的东西，也没怎么想研究过它里面的原理。我想，这也是太多数大学生的一种心理吧，觉得只会用这行了。

现在我写的这个东东，也不是我原创的，我也是参照前人的，可以说是基本上和前人的一样，没有改善，

就是照着前人的来写。

 

在spring中的，依赖注入是通过xml来配置，在这里，也是一样，通过dom4j来读取xml配置文件，主要通过实现ElementHandler接口来处理xml元素

 

第一步：先创建实体Bean，一个Person类，一个Persons类

Person类

package com.ioc.bean;

/**
 * @author chenpeng
 * @create_time Aug 10, 2010 8:58:30 AM
 * @email  [email protected]
 * @usage  //todo
 */
public class Person {
	
	private String name;
	private int age;
	private float height;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public float getHeight() {
		return height;
	}
	public void setHeight(float height) {
		this.height = height;
	}
	
	
	

}

 

 Persons类

package com.ioc.bean;

public class Persons {
	
	private Person i;
	private Person you;
	public Person getI() {
		return i;
	}
	public void setI(Person i) {
		this.i = i;
	}
	public Person getYou() {
		return you;
	}
	public void setYou(Person you) {
		this.you = you;
	}
	
	

}

 

 

第二步：写xml配置文件

 

ioc_config.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans>
	<bean id="me" class="com.ioc.bean.Person">
		<property name="name">
			<value>chenpeng</value>
		</property>
		<property name="age">
			<value>24</value>
		</property>
		<property name="height">
			<value>1.78</value>
		</property>
	</bean>
	<bean id="you" class="com.ioc.bean.Person">
		<property name="name">
			<value>ying</value>
		</property>
		<property name="age">
			<value>22</value>
		</property>
		<property name="height">
			<value>1.58</value>
		</property>
	</bean>
	<bean id="us" class="com.ioc.bean.Persons">
		<property name="i">
			<ref bean="me" />
		</property>
		<property name="you">
			<ref bean="you" />
		</property>
	</bean>
	
</beans>

 

 

第三步：xml的操作类，读取xml的内容，根据xml的标签进行依次读取，用户可以通过getBean(beanId)方法来获取bean.

 BeanFactory类

/**
 * 
 */
package com.ioc.factory;

import java.io.File;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

import org.dom4j.Attribute;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.ElementHandler;
import org.dom4j.ElementPath;
import org.dom4j.io.SAXReader;



/**
 * @author chenpeng
 * @create_time Aug 10, 2010 9:02:23 AM
 * @email  [email protected]
 * @usage  //todo
 */
public class BeanFactory {
	
	private Map<String,Object> beanMap=new HashMap<String,Object>();
	
	/**
	 * 初始化xml文件
	 * */
	public void init(String xmlUrl){
		SAXReader  saxReader=new SAXReader();
		File file=new File(xmlUrl);
		try{
			saxReader.addHandler("/beans/bean",new BeanHandler());
			saxReader.read(file);
		}
		catch(DocumentException e){
			System.out.println(e.getMessage());
		}
	}
	
	/**
	 * 根据beanid来获取bean
	 * */
	public Object getBean(String beanId){
		Object obj=null;
		obj=beanMap.get(beanId);
		return obj;
		
	}
	
	private void setFieldValue(Object obj, Field field, String value) {
		String fieldType=field.getType().getSimpleName();
		try{
			if("int".equals(fieldType)){
				field.setInt(obj, new Integer(value));
			}else if("float".equals(fieldType)){
				field.setFloat(obj, new Float(value));
			}else{
				field.set(obj,value);
			}
		}
		catch(Exception e){
			e.printStackTrace();
		}
		
	}
	
	private void setFieldValue(Object obj, Field field, Object bean) {
		try {
			field.set(obj, bean);
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		}
	}
	
	
/*************************以下是标签处理器***************************************/
	
	/**
	 * 处理/beans/bean标签
	 * */
	class BeanHandler implements ElementHandler {

		private Object obj=null;
		
		public void onStart(ElementPath path) {
			
			Element beanElement=path.getCurrent();      //获取当前的元素
			Attribute classAttribute=beanElement.attribute("class");  //获取class属性
			
			Class<?> bean=null;
			
			try{
				//根据类名通过反射构造一个class
				bean=Class.forName(classAttribute.getText()); 
			}
			catch(ClassNotFoundException e){
				e.printStackTrace();
			}
			//获取bean中的所有的域
			Field fields[]=bean.getDeclaredFields();
			Map<String,Field> fieldMap=new HashMap<String,Field>();
			
			//所有的域放在一个map中
			for(Field field:fields){
				fieldMap.put(field.getName(), field);
			}
			
			try{
				obj=bean.newInstance(); //构造出一个bean实例对象
			}
			catch(Exception e){
				e.printStackTrace();
			}
			
			//为property标签增加handler
			path.addHandler("property", new PropertyHandler(fieldMap,obj));

		}




		public void onEnd(ElementPath path) {
			Element currentElement=path.getCurrent();
			Attribute idAttribute=currentElement.attribute("id");
			beanMap.put(idAttribute.getText(), obj);
			
			//去掉property处理器
			path.removeHandler("property");
			
		}

	}
	
	
	/**
	 * 处理property标签
	 * */
	class PropertyHandler implements ElementHandler {
		
		private Map<String,Field> fieldMap;
		private Object obj;
		
		public PropertyHandler(Map<String,Field> fieldMap,Object obj){
			this.fieldMap=fieldMap;
			this.obj=obj;
			
		}

		public void onEnd(ElementPath path) {
			path.removeHandler("value");
			path.removeHandler("ref");

		}

		public void onStart(ElementPath path) {
			Element propertyElement=path.getCurrent();
			Attribute nameAttribute=propertyElement.attribute("name");
			path.addHandler("value", new ValueHandler(fieldMap,obj,nameAttribute));
			path.addHandler("ref", new RefHandler(fieldMap,obj,nameAttribute));

		}

	}
	
	
	
	/**
	 * 处理value标签
	 * */
	class ValueHandler implements ElementHandler{
		
		private Map<String,Field> fieldMap;
		private Object obj;
		private Attribute nameAttribute;
		
		public ValueHandler(Map<String,Field> fieldMap,Object obj,Attribute nameAttribute){
			this.fieldMap=fieldMap;
			this.obj=obj;
			this.nameAttribute=nameAttribute;
			
		}

		public void onEnd(ElementPath path) {
			Element valueElement=path.getCurrent();
			String strValue=valueElement.getText();
			Field tempField=fieldMap.get(nameAttribute.getValue());
			if(tempField!=null){
				tempField.setAccessible(true);
				
				//设置bean的属性的值
				setFieldValue(obj,tempField,strValue);
			}
			
		}

		public void onStart(ElementPath arg0) {
		}
		
	}
	
	

	/**
	 * 处理ref标签
	 * */
	class RefHandler implements ElementHandler{
		
		private Map<String,Field> fieldMap;
		private Object obj;
		private Attribute nameAttribute;
		private Object bean;
		
		public RefHandler(Map<String,Field> fieldMap,Object obj,Attribute nameAttribute){
			this.fieldMap=fieldMap;
			this.obj=obj;
			this.nameAttribute=nameAttribute;
			
		}

		public void onEnd(ElementPath arg0) {
			Field tempField=fieldMap.get(nameAttribute.getValue());
			if(tempField!=null){
				tempField.setAccessible(true);
				
				//设置bean的属性的值
				setFieldValue(obj,tempField,bean);
			}
			
		}

		public void onStart(ElementPath path) {
			Element refElement=path.getCurrent();
			Attribute beanAttribute=refElement.attribute("bean");
			bean=getBean(beanAttribute.getValue());
			
			
		}

		
	}
	
	

}

 

 

第四步：通过测试单元来进行测试

package com.ioc.bean;

import com.ioc.factory.BeanFactory;

import junit.framework.TestCase;

public class TestIOC extends TestCase {
	
	public void TestIOCBeans(){
		String xmlUrl="src/ioc_config.xml";
		BeanFactory factory=new BeanFactory();
		factory.init(xmlUrl);
		Person me=(Person)factory.getBean("me");
		System.out.println("me's name:"+me.getName());
		System.out.println("me's age:"+me.getAge());
		System.out.println("me's height:"+me.getHeight());
		
		
		Person you=(Person)factory.getBean("you");
		System.out.println("you's name:"+you.getName());
		System.out.println("you's age:"+you.getAge());
		System.out.println("you's height:"+you.getHeight());
		
		Persons us=(Persons)factory.getBean("us");
		System.out.println(us.getI());
		System.out.println(us.getYou());
		System.out.println(us.getI().equals(me));
		System.out.println(us.getYou().equals(you));
	}

}

 

 

测试结果如下:

me's name:chenpeng
me's age:24
me's height:1.78
you's name:ying
you's age:22
you's height:1.58
com.ioc.bean.Person@4b035d
com.ioc.bean.Person@ca0115
true
true

 

 

不知道什么原因，工程文件老是上传不成功，上传到一半就显示找不到页面了