private Map<String, Object> beanMap = new HashMap<>();

public SimpleIOC(String location) throws Exception {

loadBean(location);

}

public Object getBean(String name) {

Object bean = beanMap.get(name);

if (bean == null) {

throw new IllegalArgumentException("there is no bean with name" + name);

}

return bean;

}

private void loadBean(String location) throws Exception {

// 加载xml配置文件

InputStream inputStream = new FileInputStream(location);

// docbuilder factory

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

// doc builder

DocumentBuilder documentBuilder = factory.newDocumentBuilder();

// doc

Document document = documentBuilder.parse(inputStream);

// element

Element element = document.getDocumentElement();

// nodes

NodeList nodes = element.getChildNodes();

// 便利<bean>标签

for (int i = 0; i < nodes.getLength(); i++) {

Node node = nodes.item(i);

if (node instanceof Element) {

Element ele = (Element) node;

String id = ele.getAttribute("id");

String className = ele.getAttribute("class");

// 加载beanClass

Class beanClass = null;

try {

beanClass = Class.forName(className);

} catch (ClassNotFoundException e) {

e.printStackTrace();

return;

}

// 创建bean

Object bean = beanClass.newInstance();

// 遍历<property>标签

NodeList propertyNodes = ele.getElementsByTagName("property");

for (int j = 0; j < propertyNodes.getLength(); j++) {

Node propertyNode = propertyNodes.item(j);

if (propertyNode instanceof Element) {

Element propertyElement = (Element) propertyNode;

String name = propertyElement.getAttribute("name");

String value = propertyElement.getAttribute("value");

// 利用反射将 bean 相关字段访问权限设为可访问

Field declaredField = bean.getClass().getDeclaredField(name);

declaredField.setAccessible(true);

if (value != null && value.length() > 0) {

// 将属性值填充到相关字段中

declaredField.set(bean, value);

} else {

String ref = propertyElement.getAttribute("ref");

if (ref == null || ref.length() == 0) {

throw new IllegalArgumentException("ref config error");

}

// 将引用填充到相关字段中

declaredField.set(bean, getBean(ref));

}

}

// 将 bean 注册到 bean 容器中

registerBean(id, bean);

}

}

}

}

private void registerBean(String id, Object bean) {

beanMap.put(id, bean);

}