手写spring ioc框架

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user.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans>
   <bean id="user1" class="com.huishao.entity.UserEntity">
       <property name="userId" value="0001"></property>
       <property name="userName" value="张三"></property>
   </bean>
   <bean id="user2" class="com.huishao.entity.UserEntity">
       <property name="userId" value="0002"></property>
       <property name="userName" value="李四"></property>
   </bean>
</beans>

userEntity.java

package com.huishao.entity;

public class UserEntity {
   private String userId;
   private String userName;
   public UserEntity(){
       System.out.println("使用反射技术，执行无参数构造函数");
   }
   public UserEntity(String userId) {
       this.userId=userId;
      System.out.println("使用反射技术执行有参构造函数 userId:"+userId);
   }

   public String getUserId() {

       return userId;
   }

   public void setUserId(String userId) {

       this.userId = userId;
   }

   public String getUserName() {

       return userName;
   }

   public void setUserName(String userName) {

       this.userName = userName;
   }

}

ClassPathXmlApplicationContext.java

package com.huishao.spring;

import java.lang.reflect.Field;
import java.util.List;

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

import com.huishao.entity.UserEntity;

public class ClassPathXmlApplicationContext {
   private String xmlPath;

   public ClassPathXmlApplicationContext(String xmlPath) {
       this.xmlPath = xmlPath;
   }

public Object getBean(String beanId) throws DocumentException, ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchFieldException, SecurityException {
       //1、读取xml配置文件
       // 获取xml解析器
       SAXReader saxReader = new SAXReader();
       // 获得document对象
       Document read = saxReader.read(this.getClass().getClassLoader().getResourceAsStream(xmlPath));
       // 获得根节点
       Element rootElement = read.getRootElement();
       System.out.println("根节点的名称: " +rootElement.getName());
       //获得元素对象
       List<Element> elements = rootElement.elements();
       Object obj = null;
       for (Element sonEle : elements) {
           //2、获取到每个bean配置，获得class地址
           //获得每个bean配置获取class地址
           String sonBeanId = sonEle.attributeValue("id");
           if(!beanId.equals(sonBeanId)){
               continue;
           }
           String beanClassPath = sonEle.attributeValue("class");
           //3、拿到class地址，进行反射技术实例化对象，使用反射api为私有属性赋值
           Class<?> forName = Class.forName(beanClassPath);
           obj = forName.newInstance();
           //拿到成员属性
           List<Element> sonSoneleme = sonEle.elements();
           for (Element element : sonSoneleme) {
               String name = element.attributeValue("name");
               String value = element.attributeValue("value");
               //使用反射技术为私有属性赋值
               Field declaredField = forName.getDeclaredField(name);
               //运行往私有属性赋值
               declaredField.setAccessible(true);
               declaredField.set(obj, value);
           }
       }
       return obj;
   }
   public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchFieldException, SecurityException, DocumentException {
       ClassPathXmlApplicationContext classPathXmlApplicationContext = new ClassPathXmlApplicationContext("user.xml");
       UserEntity user = (UserEntity) classPathXmlApplicationContext.getBean("user1");
       System.out.println(user.getUserId() + "---" +user.getUserName());
   }
}

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