手寫springIOC(基於dom4j解析xml)

applicationContext.xml

<beans>
    <bean id="user1" class="com.company.User">
        <property name="userId" value="1"></property>
        <property name="userName" value="李四"></property>
    </bean>
    <bean id="user2" class="com.company.User">
        <property name="userId" value="2"></property>
        <property name="userName" value="張三"></property>
    </bean>
</beans>

User.java

package com.company;

/**
 * 手寫springioc
 * 
 * @author 000
 *
 */
public class User {
	private String userId;
	private String userName;

	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;
	}

	@Override
	public String toString() {
		return "User [userId=" + userId + ", userName=" + userName + "]";
	}

}

ClassPathXmlApplicationContext.java

package com.company;

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

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

public class ClassPathXmlApplicationContext {
	private String configFilePath;

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

	/*
	 * dom4j解析
	 */
	public Object getBean(String id) throws Exception {
		// 解析xml
		SAXReader reader = new SAXReader();
		InputStream inputStream = ClassLoader.getSystemResourceAsStream(configFilePath);
		Document document = reader.read(inputStream);
		if (document == null) {
			return null;
		}
		// 從項目根目錄下讀取
		Element root = document.getRootElement();

		// 獲取節點資源
		List<Element> list = root.elements();
		if (list.size() <= 0) {
			return null;
		}
		Object obj = null;
		for (Element element : list) {
			String idString = element.attributeValue("id");
			if (!id.equals(idString)) {
				continue;
			}
			// 獲取bean的class地址
			String classString = element.attributeValue("class");
			// 發射實例化bean
			Class<?> class1 = Class.forName(classString);
			obj = class1.newInstance();
			// 獲取子類對象
			List<Element> elements = element.elements();
			if (elements.size() <= 0) {
				return null;
			}
			for (Element element2 : elements) {
				String name = element2.attributeValue("name");
				System.out.println(name);
				String value = element2.attributeValue("value");
				// 使用反射爲對象賦值
				Field field = class1.getDeclaredField(name);
				field.setAccessible(true);
				field.set(obj, value);
			}
		}
		return obj;

	}

}