自定义实现spring式的IOC

偏执的太偏执、 2022-08-09 14:45 174阅读 0赞

这两天想好好学习一下spring，对于spring的东西无非就是一些配置，但是不想只停留在应用的层面。一直以来对spring的内部的运行的原理非常好奇，想着研究一下源码，但是把源码拿过来如大海捞针，实在是无从下手，于是乎，自己综合查了的一些资料实现了spring式的IOC，感觉很有意思。下边把代码贴出来：

首先是定义了两个测试用的接口：

package com.ioc.dao;
    
    public interface Car {
    	
    	void cleanCar();
    	
    }

package com.ioc.dao;
    
    public interface CarService {
    	void sell();
    }

和两个接口的实现：

package com.ioc.dao.impl;
    
    import com.ioc.dao.Car;
    
    public class CarImpl implements Car {
    
    	@Override
    	public void cleanCar() {
    		System.out.println("正在进行洗车！");
    	}
    
    }

package com.ioc.dao.impl;
    
    import com.ioc.dao.Car;
    import com.ioc.dao.CarService;
    
    public class CarServiceImpl implements CarService {
    
    	private Car car;
    	
    	public Car getCar() {
    		return car;
    	}
    	public void setCar(Car car) {
    		this.car = car;
    	}
    	
    	@Override
    	public void sell() {
    		car.cleanCar();
    	}
    }

以上四个类或者是接口用于测试，主要是验证依赖注入

BeanObject这个类用于处理xml文件中bean的对象，List集合用于接收属性

package com.ioc.realize;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /**
     * 对应于xml文件中的
     * <bean id="car" class="com.ioc.dao.impl.CarImpl"></bean>  
     * Copyright 2015年10月27日
     * created by txxs
     * all right reserved
     */
    public class BeanObject {
    	
    	private String id;
    	private String className;
    	//属性集合
    	private List<AttributeObject> propertys = new ArrayList<AttributeObject>();
    	
    	public BeanObject(String id, String className) {
    		this.id = id;
    		this.className = className;
    	}
    	
    	public String getId() {
    		return id;
    	}
    	public void setId(String id) {
    		this.id = id;
    	}
    	public String getClassName() {
    		return className;
    	}
    	public void setClassName(String className) {
    		this.className = className;
    	}
    	public List<AttributeObject> getPropertys() {
    		return propertys;
    	}
    	public void setPropertys(List<AttributeObject> propertys) {
    		this.propertys = propertys;
    	}
    	
    }

AttributeObject这个类用来处理XML中的属性

package com.ioc.realize;
    
    /**
     * 存放属性的对象，对应
     *  <property name="car" ref="car"></property>
     * Copyright 2015年10月27日
     * created by txxs
     * all right reserved
     */
    public class AttributeObject {
    	
    	private String name;
    	private String ref;
    	
    	public AttributeObject(String name, String ref) {
    		this.name = name;
    		this.ref = ref;
    	}
    	
    	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;
    	}
    
    }

下边就是自己的上下文SelfClassPathXMLApplicationContext，首先读取XML文件，读取完成后建立bean和属性的集合，然后实例化bean，再将依赖的bean注入

package com.ioc.realize;
    
    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.dom4j.Document;
    import org.dom4j.Element;
    import org.dom4j.XPath;
    import org.dom4j.io.SAXReader;
    
    public class SelfClassPathXMLApplicationContext {
    	
    	private List<BeanObject> beanObjects = new ArrayList<BeanObject>();  
        private Map<String, Object> sigletons = new HashMap<String, Object>();  
          
        public SelfClassPathXMLApplicationContext(String filename){  
            this.readXML(filename);  
            this.instanceBeans();  
            this.injectObject();  
        }  
        /** 
         * 为bean对象的属性注入值 
         */  
        private void injectObject() {  
            for(BeanObject beanObject : beanObjects){  
                Object bean = sigletons.get(beanObject.getId());  
                if(bean!=null){  
                    try {  
                        PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();  
                        for(AttributeObject property : beanObject.getPropertys()){  
                            for(PropertyDescriptor properdesc : ps){  
                                if(property.getName().equals(properdesc.getName())){  
                                	Method setter = properdesc.getWriteMethod();//获取属性的setter方法   
                                    if(setter!=null){  
                                        Object value = sigletons.get(property.getRef());  
                                        setter.setAccessible(true);  
                                        setter.invoke(bean, value);//把引用对象注入到属性  
                                    }  
                                    break;  
                                }  
                            }  
                        }  
                    } catch (Exception e) {  
                    }  
                }  
            }  
        }  
        /** 
         * 完成bean的实例化 
         */  
        private void instanceBeans() {  
            for(BeanObject beanObject : beanObjects){  
                try {  
                	String aa = beanObject.getClassName().trim();
                    if(beanObject.getClassName()!=null && !"".equals(beanObject.getClassName().trim()))
                    	sigletons.put(beanObject.getId(),Class.forName(beanObject.getClassName()).newInstance());  
                } catch (Exception e) {  
                    e.printStackTrace();  
                }  
            }  
              
        }  
        /** 
         * 读取xml配置文件 
         * @param filename 
         */  
        private void readXML(String filename) {
        	//创建xml解析对象
        	SAXReader saxReader = new SAXReader();
            Document document=null;     
            try{  
               //filename不能以'/'开头时,path是从ClassPath根下获取
               URL xmlpath = this.getClass().getClassLoader().getResource(filename);  
               //读取XML文件,获得document对象
               document = saxReader.read(xmlpath);  
               Map<String,String> nsMap = new HashMap<String,String>(); 
               //加入命名空间
               nsMap.put("ns","http://www.yours.org/beans");  
               //创建beans/bean查询路径 
               XPath xsub = document.createXPath("//ns:beans/ns:bean"); 
               //设置命名空间  
               xsub.setNamespaceURIs(nsMap);
               //获取文档下所有bean节点  
               List<Element> beans = xsub.selectNodes(document); 
               for(Element element: beans){  
            	   	//获取id属性值  
            	   	String id = element.attributeValue("id");
            	   	//获取class属性值   
                    String clazz = element.attributeValue("class");        
                    BeanObject beanObject = new BeanObject(id, clazz);  
                    XPath propertysub =  element.createXPath("ns:property");
                    //设置命名空间  
                    propertysub.setNamespaceURIs(nsMap);
                    List<Element> propertys = propertysub.selectNodes(element);  
                    for(Element property : propertys){                    
                        String propertyName = property.attributeValue("name");//元素内部引用的属性也获取  
                        String propertyref = property.attributeValue("ref");  
                        AttributeObject attributeObject = new AttributeObject(propertyName, propertyref);  
                        beanObject.getPropertys().add(attributeObject);  
                    }  
                    beanObjects.add(beanObject);  
                 }   
                }catch(Exception e){     
                    e.printStackTrace();  
                }  
        }  
        /** 
         * 获取bean实例 
         * @param beanName 
         * @return 
         */  
        public Object getBean(String beanName){  
            return this.sigletons.get(beanName);  
        }  
    }

测试类：

package com.ioc.test;
    
    import com.ioc.dao.CarService;
    import com.ioc.realize.SelfClassPathXMLApplicationContext;
    
    public class SpringIocTest {
    	 
    	 public static void main(String args[]){
    		 SelfClassPathXMLApplicationContext ctx = new SelfClassPathXMLApplicationContext("IocConfig.xml");  
    		 CarService carService = (CarService)ctx.getBean("carService");  
    		 carService.sell();
    	 }
    }

输出结果：

正在进行洗车！

下边是一些资料：

http://uule.iteye.com/blog/2059920

http://dingjun1.iteye.com/blog/210165

http://lgbolgger.iteye.com/category/322988

http://www.iteye.com/topic/1125248