Spring IOC容器模拟实现-优快云博客

本文链接：https://blog.youkuaiyun.com/u012500127/article/details/18423371

持久层部分请参考前面hibernate demo一文

services.xml ：

<?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/aop
 http://www.springframework.org/schema/aop/spring-aop-3.0.xsd ">
	<bean id="daoimpl" class="com.darcy.note.persistance.UserDAOImpl"></bean>
	<bean id="chinese" class="com.darcy.note.spring.Chinese">
		<property name="name">
			<value>小明</value>
		</property>
		<property name="age">
			<value>12</value>
		</property>
		<property name="list">
			<list>
				<value>aa</value>
				<value>bb</value>
			</list>
		</property>
		<property name="dao">
			<ref bean="daoimpl" />
		</property>
	</bean>
	<bean id="american" class="com.darcy.note.spring.American">
		<constructor-arg index="0">
			<ref bean="daoimpl" />
		</constructor-arg>
		<property name="sb">
			<value>sbbb</value>
		</property>
	</bean>
</beans>

模拟spring核心的 BeanPool.java ：

package com.darcy.note.spring;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.LinkedList;
import java.util.List;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class BeanPool {
	private String path;

	public BeanPool(String path) {
		this.path = path;
	}

	public Object getBean(String beanid) throws Exception {
		InputStream stream = this.getClass().getResourceAsStream(path);
		Document document = getDoc(stream);
		if (document == null) {
			return null;
		}
		return getBean(beanid, document);
	}

	private Document getDoc(InputStream stream) {
		try {
			return DocumentBuilderFactory.newInstance().newDocumentBuilder()
					.parse(stream);
		} catch (SAXException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ParserConfigurationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;
	}

	private Object getBean(String beanid, Document doc) throws Exception {
		Element root = doc.getDocumentElement();
		Element bean = getElement(root, "bean", "id", beanid);
		Object ret = getBean(bean);
		return ret;
	}

	private Object getBean(Element bean) throws Exception {
		if (bean != null) {
			String clazz = bean.getAttribute("class");
			if (clazz != null) {
				// 仅模拟简单情况，不支持构造器注入参数
				Object obj = Class.forName(clazz).newInstance();
				List<Element> properties = getElements(bean, "property");
				for (Element e : properties) {
					String name = e.getAttribute("name");
					if (name == null) {
						continue;
					}
					setValue(obj, name, e);
				}
				return obj;
			}
		}
		return null;
	}

	private void setValue(Object obj, String name, Element element)
			throws Exception {
		String setMethod = getSetMethodName(name);
		List<Element> valueList = getElements(element, "value");
		// value
		if (!valueList.isEmpty()) {
			String value = valueList.get(0).getTextContent();
			Field f = obj.getClass().getDeclaredField(name);
			// 支持Integer类型和String类型
			if (f.getType().getName().equals("int")) {
				obj.getClass().getMethod(setMethod, int.class)
						.invoke(obj, Integer.parseInt(value));
			} else {
				obj.getClass().getMethod(setMethod, String.class)
						.invoke(obj, value);
			}
		} else {
			List<Element> listList = getElements(element, "list");
			// list
			if (!listList.isEmpty()) {
				List<Element> values = getElements(listList.get(0), "value");
				List<String> list = new LinkedList<String>();
				for (Element value : values) {
					list.add(value.getTextContent());
				}
				obj.getClass().getMethod(setMethod, List.class)
						.invoke(obj, list);
			} else {
				// ref
				String beanid = getElements(element, "ref").get(0)
						.getAttribute("bean");
				Object refObj = getBean(beanid, element.getOwnerDocument());
				Method[] methods = obj.getClass().getMethods();
				for (Method method : methods) {
					if (method.getName().equals(setMethod)) {
						method.invoke(obj, refObj);
						break;
					}
				}
			}
		}
	}

	private String getSetMethodName(String name) {
		return "set" + name.substring(0, 1).toUpperCase() + name.substring(1);
	}

	private Element getElement(Element root, String tagName, String attr,
			String attrValue) {
		NodeList list = root.getElementsByTagName(tagName);
		for (int i = 0; i < list.getLength(); i++) {
			Node node = list.item(i);
			if (node.getNodeType() == Node.ELEMENT_NODE) {
				Element e = (Element) node;
				String value = e.getAttribute(attr);
				if (value != null && value.equals(attrValue)) {
					return e;
				}
			}
		}
		return null;
	}

	private List<Element> getElements(Element root, String tagName) {
		NodeList list = root.getChildNodes();
		List<Element> elist = new LinkedList<Element>();
		for (int i = 0; i < list.getLength(); i++) {
			Node node = list.item(i);
			if (node.getNodeName().equals(tagName)
					&& node.getNodeType() == Node.ELEMENT_NODE) {
				Element e = (Element) node;
				elist.add(e);
			}
		}
		return elist;
	}
}

接口 Person.java ：

package com.darcy.note.spring;

public interface Person {
	void speak();
}

服务实例 Chinese.java ：

package com.darcy.note.spring;

import java.util.List;

import com.darcy.note.persistance.User;
import com.darcy.note.persistance.UserDAO;

public class Chinese implements Person {
	private String name;
	private int age;
	private List<String> list;
	private UserDAO dao;

	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 void speak() {
		System.out.println("a chinese name " + this.name + ", age " + this.age
				+ ", list " + list.get(0));
		User user = new User();
		user.setName(name);
		user.setPassword(String.valueOf(age));
		user.setType(null);
		dao.save(user);
	}

	public List<String> getList() {
		return list;
	}

	public void setList(List<String> list) {
		this.list = list;
	}

	public UserDAO getDao() {
		return dao;
	}

	public void setDao(UserDAO dao) {
		this.dao = dao;
	}
}

测试类：

package com.darcy.note.spring;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
	public static void main(String[] args) throws Exception {
		// ApplicationContext context = new ClassPathXmlApplicationContext(
		// "/services.xml");
		BeanPool context = new BeanPool("/services.xml");
		Person p = (Person) context.getBean("chinese");
		p.speak();
		// p = (Person) context.getBean("american");
		// p.speak();
	}
}

spring demo