手写Spring IOC XML版本注入bean

public class ClassPathXmlApplicationContext {
	// xml路径地址
	private String xmlPath;

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

	public Object getBean(String beanId) throws Exception {
		// 1. 读取配置文件
		List elements = readerXml();
		if (elements == null) {
			throw new Exception("该配置文件没有子元素");
		}
		// 2. 使用beanId查找对应的class地址
		String beanClass = findXmlByIDClass(elements, beanId);
		if (StringUtils.isEmpty(beanClass)) {
			throw new Exception("未找到对应的class地址");
		}
		// 3. 使用反射机制初始化，对象
		Class forName = Class.forName(beanClass);
		return forName.newInstance();
	}

	// 读取配置文件信息
	public List readerXml() throws documentException {
		SAXReader saxReader = new SAXReader();
		if (StringUtils.isEmpty(xmlPath)) {
			new Exception("xml路径为空...");
		}
		document read = saxReader.read(getClassXmlInputStream(xmlPath));
		// 获取根节点信息
		Element rootElement = read.getRootElement();
		// 获取子节点
		List elements = rootElement.elements();
		if (elements == null || elements.isEmpty()) {
			return null;
		}
		return elements;
	}

	// 使用beanid查找该Class地址
	public String findXmlByIDClass(List elements, String beanId) throws Exception {
		for (Element element : elements) {
			// 读取节点上是否有value
			String beanIdValue = element.attributevalue("id");
			if (beanIdValue == null) {
				throw new Exception("使用该beanId为查找到元素");
			}
			if (!beanIdValue.equals(beanId)) {
				continue;
			}
			// 获取Class地址属性
			String classPath = element.attributevalue("class");
			if (!StringUtils.isEmpty(classPath)) {
				return classPath;
			}
		}
		return null;
	}

	// 读取xml配置文件
	public InputStream getClassXmlInputStream(String xmlPath) {
		InputStream resourceAsStream = getClass().getClassLoader().getResourceAsStream(xmlPath);
		return resourceAsStream;
	}

}