简单实现spring里的BeanFactory实现原理

首先我们先创建一个BeanFactory借口：

/*** Project Name:springAnalog* File Name:BeanFactory.java* Package Name:com.iflytek.beanfactory* Date:2015-11-20下午09:40:50* Copyright (c) 2015, [e-mail] All Rights Reserved.**/package com.iflytek.beanfactory;public interface BeanFactory{    /**     * getBean:(定义一个获取bean的方法). <br/>     * @author syzhao     * @param id      * @return     * @since JDK 1.6     */    public Object getBean(String id);}

我们继续在创建一个实现BeanFactory类 ClassPathXmlApplicationContext这是最重要的：

/*** Project Name:springAnalog* File Name:ClassPathXmlApplicationContext.java* Package Name:com.iflytek.beanfactory* Date:2015-11-20下午09:43:20* Copyright (c) 2015, [e-mail] All Rights Reserved.**/package com.iflytek.beanfactory;import java.util.HashMap;import java.util.List;import java.util.Map;import org.dom4j.Document;import org.dom4j.DocumentException;import org.dom4j.Element;import org.dom4j.io.SAXReader;public class ClassPathXmlApplicationContext implements BeanFactory{    //定义一个filePath变量    private String filePath;        //首先定义Map 目的来存放生产的对象    Map<String, Object> map = new HashMap<String, Object>();        public ClassPathXmlApplicationContext(String filePath)    {        //获取配置文件路径        this.filePath = filePath;        //初始化        try        {            this.readFile();        }        catch (Exception e)        {            e.printStackTrace();        }    }        /**     * readFile:(读取文件). <br/>     * @author syzhao     * @throws DocumentException      * @throws ClassNotFoundException      * @throws IllegalAccessException      * @throws InstantiationException      * @since JDK 1.6     */    private void readFile()        throws DocumentException, InstantiationException, IllegalAccessException, ClassNotFoundException    {        //接下来，用dom4j来解析，，，dom4j下载地址：http://sourceforge.net/projects/dom4j        SAXReader reader = new SAXReader();        //获取根节点        Document document = reader.read(this.getClass().getClassLoader().getResourceAsStream(filePath));        //获取bean所有的元素        List<Element> list = document.selectNodes("/beans/bean");        for (int i = 0; i < list.size(); i++)        {            //获取bean的id            String id = list.get(i).attributeValue("id");            //获取bean的class也就是类的路径            String classpath = list.get(i).attributeValue("class");            //利用反射获取对象  有三种方式，，，我们通过类的全名+包名来生成            Object object = Class.forName(classpath).newInstance();                        //放到我们定义的map里 key =id ,vlaue =获取的对象，为下面getBean（）取对象提供条件            map.put(id, object);        }    }        @Override    public Object getBean(String id)    {        //这里根据id来获取对于的对象既可        return map.get(id);    }    }

接下来我们定义一个person借口

/*** Project Name:springAnalog* File Name:Person.java* Package Name:com.iflytek.person* Date:2015-11-20下午10:39:27* Copyright (c) 2015, [e-mail] All Rights Reserved.**/package com.iflytek.person;public interface Person{    public void work();}

我们用student和teacher实现person借口：

Student类：

/*** Project Name:springAnalog* File Name:Student.java* Package Name:com.iflytek.person* Date:2015-11-20下午10:40:42* Copyright (c) 2015, [e-mail] All Rights Reserved.**/package com.iflytek.person;public class Student implements Person{    @Override    public void work()    {        //输出一句话        System.out.println("学生的工作是：认真学习！");    }    }

Teacher类：

/*** Project Name:springAnalog* File Name:Teacher.java* Package Name:com.iflytek.person* Date:2015-11-20下午10:41:42* Copyright (c) 2015, [e-mail] All Rights Reserved.**/package com.iflytek.person;public class Teacher implements Person{    @Override    public void work()    {        //输出一句话        System.out.println("老师的工作是：认真教书！！");            }    }

接下来我们创建一个xml：applicationContext.xm

 

<?xml version="1.0" encoding="UTF-8"?><beans>    <bean id="student" class="com.iflytek.person.Student"/>    <bean id="teacher" class="com.iflytek.person.Teacher"/></beans>

好了，我们进行测试：

创建test类：

/*** Project Name:springAnalog* File Name:Test.java* Package Name:com.iflytek* Date:2015-11-20下午10:45:20* Copyright (c) 2015, [e-mail] All Rights Reserved.**/package com.iflytek;import com.iflytek.beanfactory.BeanFactory;import com.iflytek.beanfactory.ClassPathXmlApplicationContext;import com.iflytek.person.Person;public class Test{    /**     * main:(这里用一句话描述这个方法的作用). <br/>     * @author syzhao     * @param args     * @since JDK 1.6     */    public static void main(String[] args)    {        BeanFactory beanFactory = new ClassPathXmlApplicationContext("applicationContext.xml");        Person person = (Person)beanFactory.getBean("student");        person.work();        person = (Person)beanFactory.getBean("teacher");        person.work();    }    }

当你运行时报了 java.lang.ClassNotFoundException: org.jaxen.JaxenException这个异常，不用怕，，

因为你少了，dom4j的另一个jar包：jaxen-1.1-beta-6.jar   这个在dom4j-1.6.1\lib下把jaxen-1.1-beta-6.jar引入既可以了，，

好了在运行一次：

结果完美呈现：

以上就是模拟了一下，，，其实spring内部远比这个复杂，需要大家努力去研究，，，，