spring ioc简易实现

深碍√TFBOYSˉ_ 2023-06-15 07:07 19阅读 0赞

### **手写spring ioc简易实现: 反射 + dom4j** ###

**beanXml的配置文件**

<?xml version="1.0" encoding="UTF-8"?>
    <beans>
    	<bean id="user1" class="com.java.es.pojo.UserEntity">
    		<property name="userId" value="0001"></property>
    		<property name="userName" value="花哥"></property>
    	</bean>
    	<bean id="user2" class="com.java.es.pojo.UserEntity">
    		<property name="userId" value="0002"></property>
    		<property name="userName" value="花少"></property>
    	</bean>
    </beans>

package com.java.es.pojo;
    
    public class UserEntity {
    	private String userId;
    	private String userName;
    
    	public UserEntity() {
    		System.out.println("使用反射执行无参数构造函数");
    	}
    
    	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;
    	}
    
    }

**实现代码**

package com.java.es.pojo;
    
    import org.dom4j.Document;
    import org.dom4j.Element;
    import org.dom4j.io.SAXReader;
    
    import java.lang.reflect.Field;
    import java.util.ArrayList;
    import java.util.List;
    
    /**
     * @author jiangli
     * @date 2019/11/20 22:40
     * 手写spring ioc实现: 反射 + dom4j
     */
    public class SpringIOC {
    	private String xmlPath;
    
    	public SpringIOC(String xmlPath) {
    		this.xmlPath = xmlPath;
    	}
    
    	public static void main(String[] args) throws Exception{
    		SpringIOC ctx = new SpringIOC("user.xml");
    		List<Object> bean = ctx.getBean();
    		for (Object o : bean) {
    			UserEntity user = (UserEntity) o;
    			System.out.println(user.getUserId() + "----" + user.getUserName());
    		}
    	}
    
    	private List<Object> getBean() throws Exception{
    		// spring 加载过程 或者spring ioc实现原理
    		// 1.读取xml配置文件
    		// 获取xml解析器
    		SAXReader saxReader = new SAXReader();
    		// this.getClass().getClassLoader().getResourceAsStream("xmlPath")
    		// 获取当前项目路径
    		Document document = saxReader.read(this.getClass().getClassLoader().getResourceAsStream(xmlPath));
    		// 获取跟节点对象
    		Element root = document.getRootElement();
    		// 获取所有子节点
    		List<Element> elements = root.elements();
    		List<Object> objects = new ArrayList<>();
    		for (Element element : elements) {
    			//使用反射创建bean
    			String className = element.attributeValue("class");
    			Class<?> forName = Class.forName(className);
    			Object object = forName.newInstance();
    			// 取所有成员属性
    			List<Element> filedElements = element.elements();
    			for (Element filedElement : filedElements) {
    				//为属性赋值
    				String name = filedElement.attributeValue("name");
    				String value = filedElement.attributeValue("value");
    				Field declaredField = forName.getDeclaredField(name);
    				//y允许为私有成员赋值
    				declaredField.setAccessible(true);
    				declaredField.set(object, value);
    			}
    			objects.add(object);
    		}
    		return objects;
    	}
    }

![20191120231300333.png][]![20191120231312768.png][]

**执行结果 **

![20191120231932264.png][]

[20191120231300333.png]: https://img-blog.csdnimg.cn/20191120231300333.png
[20191120231312768.png]: https://img-blog.csdnimg.cn/20191120231312768.png
[20191120231932264.png]: https://img-blog.csdnimg.cn/20191120231932264.png