spring 加载xml 创建实例对象demo

第一次写博客，也不知道咋写。就直接上代码了。写完了这个demo后可以加深对spring 如何创建对象的理解

package org.example;

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

import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
 * 工厂接口实现类
 *
 *
 * */
public class MyClasssXmlComplacation implements MyFactory {
    //定义map对象用来存放id与class属性
    private Map<String, Object> beanMap=new HashMap<>();
    //定义集合存放配置文件中bean
    List<MyBean> myBeanList;
    public MyClasssXmlComplacation(String fileName) throws DocumentException, IllegalAccessException, InstantiationException, ClassNotFoundException {
//        解析配置文件
        parseXml(fileName);
        instanceBean();
    }
    private void instanceBean() throws ClassNotFoundException, IllegalAccessException, InstantiationException {
        for (MyBean myBean:myBeanList){
            Object o = Class.forName(myBean.getClazz()).newInstance();
            beanMap.put(myBean.getId(),o);
        }
    }
    private void parseXml(String fileName) throws DocumentException {
        SAXReader saxReader =new SAXReader();
        URL resource = this.getClass().getClassLoader().getResource(fileName);
        Document document =saxReader.read(resource);
        XPath xPath =document.createXPath("beans/bean");
        List<Element> elements =xPath.selectNodes(document);
        if(elements!=null&&elements.size()>0){
            myBeanList =new ArrayList<>();
            for (Element element:elements){
                String id = element.attributeValue("id");
                String aClass = element.attributeValue("class");
                MyBean myBean = new MyBean(id, aClass);
                myBeanList.add(myBean);
            }
        }
    }
    @Override
    public Object getBean(String id) {
        Object id1 = beanMap.get(id);
        return id1;
    }
}

package org.example;
//放取配置文件的id与class属性值

/**
 *实体类
 */
public class MyBean {
    private String id;
    private String clazz;

    public MyBean() {
    }

    public MyBean(String id, String clazz) {
        this.id = id;
        this.clazz = clazz;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getClazz() {
        return clazz;
    }

    public void setClazz(String clazz) {
        this.clazz = clazz;
    }

    @Override
    public String toString() {
        return "MyBean{" +
                "id='" + id + '\'' +
                ", clazz='" + clazz + '\'' +
                '}';
    }
}

/**
* 模拟工厂接口
*/

package org.example;

public interface MyFactory {

    public Object getBean (String id);
}

xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans>
    <bean id="userDao" class="org.example.UserDao"></bean>
    <bean id="user01Service" class="org.example.User01Service"></bean>
</beans>

maven依赖

 <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.4.RELEASE</version>
        </dependency>
<!--        读取配置文件-->
        <dependency>
            <groupId>dom4j</groupId>
            <artifactId>dom4j</artifactId>
            <version>1.6.1</version>
        </dependency>
        <dependency>
            <groupId>jaxen</groupId>
            <artifactId>jaxen</artifactId>
            <version>1.1.6</version>
        </dependency>
    </dependencies>
/**
*调用
*/

package org.example;

import org.dom4j.DocumentException;

public class Start {
    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, DocumentException, IllegalAccessException {
        //得到spring 上下文环境
//        ApplicationContext app=new ClassPathXmlApplicationContext("spring.xml");
//        UserService userService = (UserService) app.getBean("userService");
//        userService.test();
      MyFactory myFactory = new MyClasssXmlComplacation("spring01.xml");
        UserDao userDao = (UserDao) myFactory.getBean("userDao");
        userDao.test();

    }
}