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DispathcerServlet Spring Web 简易框架

   约 1328 字   预计阅读 3 分钟    次阅读  
目录

DispathcerServlet Spring Web 简易框架

  1. 准备 applicationContext.xml 对应 bean

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    <?xml version="1.0" encoding="UTF-8"?>
<beans>
    <bean id="fruitDao" class="com.test.dao.FruitDao"/>

    <bean id="fruitService" class="com.test.service.impl.FruitServiceImpl">
        <property name="fruitDao" ref="fruitDao"/>
    </bean>

    <bean id="fruit" class="com.test.controller.FruitController">
        <property name="fruitService" ref="fruitService"/>
    </bean>
</beans>

  2. 通过实现 ServletContextListener 监听器接口，并重写 contextInitialized 方法获取 BeanFactory 对象放入 ServletContext 域中

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    // 创建 BeanFactory 对象
BeanFactory beanFactory = new ClassPathXmlApplicationContext();
ServletContext application = ServletContextEvent.getServletContext();
// 放入应用域总中
application.setAttribute("beanFactory", beanFactory);

  3. 新建 BeanFactory 接口，并创建 ClassPathXmlApplicationContext 实现类通过 applicationContext.xml 文件获取相对应的 bean

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    // 转化 path 为流
InputStream is = this.getClass().getClassLoader().getResourceAsStream(path);
// 获取 document 对象
DocumentBuildFactory dbf = DocumentBuildFactory.newInstance();
DocumentBuild db = dbf.newDocumentBuild();
Document doc = db.parse(is);

  4. 遍历节点找到元素节点加入到 beanMap 中

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    // 获取 nodeList
NodeList nodeList = doc.getDocumentElement();
// 将 bean 节点放入 beanMap
for (int i = 0; i < nodeList.getLength(); i++) {
	Node node = NodeList.item(i);
		if (node.getNodeType() == Node.ELEMENT_NODE) {
			Element element = (Element) node;
			String id = element.getAttribute("id");
			String clazz = element.getAttribute("class");
			// 反射获取 class
			Object beanObj = Class.forName(clazz).newInstance();
			beanMap.put(id, beanObj);
	}
}

  5. 再次循环进行依赖注入

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    for (int i = 0; i < nodeList.getLength(); i++) {
	Node node = nodeList.item(i);
	if (node.getNodeType() == Node.ELEMENT_NODE) {
		// 获取子节点 property
		Element baseBean = (Element) node;
		String baseId = baseBean.getAttribute("id");
		NodeList childNodes = node.getChildNodes();
		for (int j = 0; j < childNodes.getLength(); j++) {
			Node property = childNodes.item(j);
			if (property.getNodeType() == Node.ELEMENT_NODE) {
				Element propertyEle = (Element) property;
				String name = propertyEle.getAttribute("name");
				String ref = propertyEle.getAttribute("ref");
				Object baseObj = beanMap.get(baseId);
				Object refObj = beanMap.get(ref);
				// 反射获取成员变量
				Field dependency = baseObj.getClass().getDeclaredField(name);
				dependency.setAccessible(true);
				// 设置依赖
				dependency.set(baseObj, refObj);
			}
		}
	}	
}

  6. 在 DispatcherServlet 类中继承 HttpServlet 并在 init() 方法中从 ServletContext 获取 beanFactory

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    public class DispatcherServlet implements HttpServlet {

	public BeanFactory beanFactory;

	@Override
	public void init () throw ServletException {
		ServletContext application = this.getServletContext();
		Object beanFactoryObj = application.getAttribute("beanFactory");
		if (beanFactoryObj != null) {
			beanFactory = (BeanFactory) beanFactory;	
		}else {
			throw new RuntimeException("Ioc 容器获取失败！");
		}
	}
}

  7. 在 DispatcherServlet service 方法中利用请求中的 operate 反射获取调用方法，并通过 url 地址从 beanFactory 获取操作的 Controller

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    public void service (HttpServletRequest request, HttpServletResponse response) throw ServletException, IOException, IllegalAccessException, InvocationTargetException {
	request.setCharacterEncoding("UTF-8");

	// 获取路径并分割
	String uri = request.getServletPath().substring(1); // /fruit?operate=add -> fruit?..
	String beanName = uri.contains("?") ? uri.substring(0, uri.indexOf("?") : uri);
	String operate = request.getParameter("operate");
	if (operate == null || "".equals(operate)) {
		operate = "index";
	}

	// 通过 beanName 获取对应实体类
	Object beanObj = Class.forName(beanName).newInstance();
	// 获取对应 operate
	Method[] methods = beanObj.getClass().getDeclaredMethods();
	for (Method method : methods) {
		String methodName = method.getName();
		if (operate.equals(methodName)) {
			// 获取参数
			Parameter[] parameter = method.getParameters();
			Object[] paramVal = new Object[parameter.length];
			for (int i = 0; i < parameters.length; i++) {
	      if (parameters[i].getType().getName().contains("request")) {
		      paramVal[i] = request;
	      } else if (parameters[i].getType().getName().contains("response")) {
		      paramVal[i] = response;
	      }
      }
			method.setAccessible(true);
			method.invoke(beanObj, paramVal);
		}
	}
}

  8. 完整代码

    • Listener

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      public class MyServletContextListener implements ServletContextListener () {

	@Override
	public void contextInitialized (ServletContextEvent servletContextEvent) {
		// 创建 BeanFactory 对象
		BeanFactory beanFactory = new ClassPathXmlApplicationContext();
		ServletContext application = ServletContextEvent.getServletContext();
		// 放入应用域总中
		application.setAttribute("beanFactory", beanFactory);
	}

	@Override
	public void contextDestroyed (ServletContextEvent servletContextEvent) {

	}
}

    • ClassPathXmlApplicationContext 实现

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      public interface BeanFactory {
	Object getBean(String id);
}

public class ClassPathXmlApplicationContext implements BeanFactory {

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

	public ClassPathXmlApplicationContext () {
		ClassPathXmlApplicationContext("applicationContext.xml");
	}
	// 初始化获取 beanMap
	public ClassPathXmlApplicationContext (String path) throw Exception {
		// 转化 path 为流
		InputStream is = this.getClass().getClassLoader().getResourceAsStream(path);
		// 获取 document 对象
		DocumentBuildFactory dbf = DocumentBuildFactory.newInstance();
		DocumentBuild db = dbf.newDocumentBuild();
		Document doc = db.parse(is);

		// 获取 nodeList
		NodeList nodeList = doc.getDocumentElement();
		// 将 bean 节点放入 beanMap
		for (int i = 0; i < nodeList.getLength(); i++) {
			Node node = NodeList.item(i);
			if (node.getNodeType() == Node.ELEMENT_NODE) {
				Element element = (Element) node;
				String id = element.getAttribute("id");
				String clazz = element.getAttribute("class");

				// 反射获取 class
				Object beanObj = Class.forName(clazz).newInstance();
				beanMap.put(id, beanObj);
			}
		}

		for (int i = 0; i < nodeList.getLength(); i++) {
			Node node = nodeList.item(i);
			if (node.getNodeType() == Node.ELEMENT_NODE) {
				// 获取子节点 property
				Element baseBean = (Element) node;
				String baseId = baseBean.getAttribute("id");
				NodeList childNodes = node.getChildNodes();
				for (int j = 0; j < childNodes.getLength(); j++) {
					Node property = childNodes.item(j);
					if (property.getNodeType() == Node.ELEMENT_NODE) {
						Element propertyEle = (Element) property;
						String name = propertyEle.getAttribute("name");
						String ref = propertyEle.getAttribute("ref");
						Object baseObj = beanMap.get(baseId);
						Object refObj = beanMap.get(ref);
						// 反射获取成员变量
						Field dependency = baseObj.getClass().getDeclaredField(name);
						dependency.setAccessible(true);

						// 设置依赖
						dependency.set(baseObj, refObj);
					}
				}
			}
		}

	}

	@Override
	public Object getBean (String id) {
		return beanMap.get(id);
	}
}

    • DispatcherServlet 中央控制器

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      public class DispatcherServlet implements HttpServlet {

	public BeanFactory beanFactory;

	@Override
	public void init () throw ServletException {
		ServletContext application = this.getServletContext();
		Object beanFactoryObj = application.getAttribute("beanFactory");
		if (beanFactoryObj != null) {
			beanFactory = (BeanFactory) beanFactory;	
		}else {
			throw new RuntimeException("Ioc 容器获取失败！");
		}
	}

	@Override
	public void service (HttpServletRequest request, HttpServletResponse response) throw ServletException, IOException, IllegalAccessException, InvocationTargetException {
		request.setCharacterEncoding("UTF-8");

		// 获取路径并分割
		String uri = request.getServletPath().substring(1); // /fruit?operate=add -> fruit?..
		String beanName = uri.contains("?") ? uri.substring(0, uri.indexOf("?") : uri);
		String operate = request.getParameter("operate");
		if (operate == null || "".equals(operate)) {
			operate = "index";
		}

		// 通过 beanName 获取对应实体类
		Object beanObj = Class.forName(beanName).newInstance();
		// 获取对应 operate
		Method[] methods = beanObj.getClass().getDeclaredMethods();
		for (Method method : methods) {
			String methodName = method.getName();
			if (operate.equals(methodName)) {
				// 获取参数
				Parameter[] parameter = method.getParameters();
				Object[] paramVal = new Object[parameter.length];
				for (int i = 0; i < parameters.length; i++) {
		      if (parameters[i].getType().getName().contains("request")) {
			      paramVal[i] = request;
		      } else if (parameters[i].getType().getName().contains("response")) {
			      paramVal[i] = response;
		      }
	      }
				method.setAccessible(true);
				method.invoke(beanObj, paramVal);
			}
		}
	}
}
更新于 2022-12-05
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