实现简单Spring基于XML的配置程序

定义一个容器，使用ConcurrentHashMap 做为单例对象的容器

先解析beans.xml
得到第一个bean对象的信息，id，class，属性和属性值
使用反射生成对象，并赋值
将创建好的bean对象放入到singletonObjects集合中
提供getBean(id)方法可以返回对应的bean对象

monster bean

public class Monster {private Integer id;private String name;private String skill;public Monster() {}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSkill() {return skill;}public void setSkill(String skill) {this.skill = skill;}@Overridepublic String toString() {return "Monster{" +"id=" + id +", name='" + name + '\'' +", skill='" + skill + '\'' +'}';}
}

package com.sparrow.spring.application;import com.sparrow.spring.bean.Monster;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;import java.io.File;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;/*** @Author: 诉衷情の麻雀* @Description: TODO* @DateTime: 2023/7/24 8:09**/
public class SpaApplicationContext {private ConcurrentHashMap<String, Object> singletonObjects = new ConcurrentHashMap<>();//构造器 接收一个容器的配置文件public SpaApplicationContext(String iocBeanXmlFile) throws Exception {//1. 得到类加载路径String path = this.getClass().getResource("/").getPath();//2.创建SaxReaderSAXReader saxReader = new SAXReader();//3.得到Document对象Document document = saxReader.read(new File(path + iocBeanXmlFile));//4.得到rootElementElement rootElement = document.getRootElement();List<Element> elements = rootElement.elements("bean");for (Element bean : elements) {String id = bean.attributeValue("id");String classFullPath = bean.attributeValue("class");Integer monsterId = null;String name = "";String skill = "";//遍历bean下面的property属性List<Element> property = bean.elements("property");for (Element elementProperty : property) {//如果是id把值存起来if ("id".equalsIgnoreCase(elementProperty.attributeValue("name"))) {monsterId = Integer.valueOf(elementProperty.attributeValue("value"));} else if ("name".equalsIgnoreCase(elementProperty.attributeValue("name"))) {name = elementProperty.attributeValue("value");} else if ("skill".equalsIgnoreCase(elementProperty.attributeValue("name"))) {skill = elementProperty.attributeValue("value");}//利用反射 根据类的全路径 进行实例化Class<?> aClass = Class.forName(classFullPath);Monster o = (Monster) aClass.newInstance();o.setId(monsterId);o.setName(name);o.setSkill(skill);//放入容器中singletonObjects.put(id, o);}}}public Object getBean(String id) {return singletonObjects.get(id);}
}

beans.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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean class="com.sparrow.spring.bean.Monster" id="monster01"><property name="id" value="1"/><property name="name" value="白骨精"/><property name="skill" value="吃唐僧"/></bean><bean class="com.sparrow.spring.bean.Monster" id="monster02"><property name="id" value="2"/><property name="name" value="老鼠精"/><property name="skill" value="吸血"/></bean></beans>

public class Test {public static void main(String[] args) throws Exception {SpaApplicationContext spaApplicationContext = new SpaApplicationContext("beans.xml");Monster monster02 = (Monster) spaApplicationContext.getBean("monster02");Monster monster01 = (Monster) spaApplicationContext.getBean("monster01");System.out.println(monster02);System.out.println(monster01);}
}