springmvc简易框架（项目中肯定不能用，只是为了了解原理)的实现思路如下:
手写spring框架
1.配置阶段
配置web.xml DispatcherServlet
设定init-param contextConfigLoacation = classpath:application.xml
设定url-pattern /*
配置Annotation @Controller @Service @Autowirted @RequestMapping …
2.初始化阶段
调用init()方法 加载配置文件
IOC容器初始化 Map<String,Object>
扫描相关的类 scan-package=“com.hfl.demo”
ioc:创建实例化并保存至容器 通过反射机制将类实例化放入IOC容器中
DI:进行DI操作:扫描IOC容器中的实例，给没有赋值的属性自动赋值
3.运行阶段
调用doPost()/doGet() - Web容器调用doPost/doGet方法，获得request/response对象
匹配HandlerMapping - 从request对象中获得用户输入的url，找到其对应的Method
反射调用method.invoker() - 利用反射调用方法并返回结果
response.getWrite().write - 将返回结果输出到浏览器
代码部分
1.配置阶段
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0"> <display-name>Gupao Web Application</display-name> <servlet> <servlet-name>hflmvc</servlet-name> <servlet-class>com.hfl.mvcframework.servlet.v1.HfDispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>application.properties</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>hflmvc</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> </web-app>
包结构:
application.properties
scanPackage=com.hfl.demo
配置注解
@Target({ElementType.FIELD}) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface HfAutowired { String value() default ""; }
其他注解类相同，只是注解名不一样.
初始化阶段
HfDispatcherServlet package com.hfl.mvcframework.servlet.v1; import com.hfl.mvcframework.annotation.HfAutowired; import com.hfl.mvcframework.annotation.HfController; import com.hfl.mvcframework.annotation.HfRequestMapping; import com.hfl.mvcframework.annotation.HfService; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.net.URL; import java.util.Arrays; import java.util.HashMap; import java.util.Map; import java.util.Properties; /** * Title: HfDispatcherServlet * Description: TODO * * @author hfl * @version V1.0 * @date 2020-06-17 */ //所有的核心逻辑全部写在一个init()方法中。 public class HfDispatcherServlet extends HttpServlet { private Map<String, Object> mapping = new HashMap<String, Object>(); @Override public void init(ServletConfig config) throws ServletException { //读取初始化参数中的 配置文件信息（为了获取扫描的基础包名） InputStream is = null; try { Properties configContext = new Properties(); is = this.getClass().getClassLoader().getResourceAsStream(config.getInitParameter("contextConfigLocation")); configContext.load(is); String scanPackage = configContext.getProperty("scanPackage"); // 扫描包下的类 加入容器中 doScanner(scanPackage); //注入bean带注解的bean 并初始化 for (String className : mapping.keySet()) { if (!className.contains(".")) { continue; } Class<?> clazz = Class.forName(className); //将<url，method>加入到mapping中 if (clazz.isAnnotationPresent(HfController.class)) { mapping.put(className, clazz.newInstance()); String baseUrl = ""; if (clazz.isAnnotationPresent(HfRequestMapping.class)) { HfRequestMapping requestMapping = clazz.getAnnotation(HfRequestMapping.class); baseUrl = requestMapping.value(); } //如果controller下的方法有 路径，则拼接到 map的value中去 Method[] methods = clazz.getMethods(); for (Method method : methods) { if (!method.isAnnotationPresent(HfRequestMapping.class)) { continue; } HfRequestMapping requestMapping = method.getAnnotation(HfRequestMapping.class); String url = (baseUrl + "/" + requestMapping.value()).replaceAll("/+", "/"); mapping.put(url, method); System.out.println("Mapped " + url + "," + method); } } else if (clazz.isAnnotationPresent(HfService.class)) { //注解中有别名 有别名替换key HfService service = clazz.getAnnotation(HfService.class); String beanName = service.value(); if (!"".equals(beanName)) { beanName = clazz.getName(); } //初始化bean Object instance = clazz.newInstance(); mapping.put(beanName, instance); //将service实现的接口也注入到bean中 for (Class<?> i : clazz.getInterfaces()) { mapping.put(i.getName(), instance); } } } //根据 autowired实例化bean 这里只实现了controller层的注入 for (Object object : mapping.values()) { if (object == null) { continue; } Class<?> clazz = object.getClass(); if (clazz.isAnnotationPresent(HfController.class)) { Field[] fields = clazz.getDeclaredFields(); for (Field field : fields) { if (!field.isAnnotationPresent(HfAutowired.class)) { continue; } HfAutowired autowired = field.getAnnotation(HfAutowired.class); String beanName = autowired.value(); if ("".equals(beanName)) { beanName = field.getType().getName(); } field.setAccessible(true); try { field.set(mapping.get(clazz.getName()), mapping.get(beanName)); } catch (Exception e) { e.printStackTrace(); } } } } } catch (Exception e) { } } /** * 扫描包下的类 加入容器中 * * @param scanPackage */ private void doScanner(String scanPackage) { // 将包路径转成url路径 URL url = this.getClass().getClassLoader().getResource("/" + scanPackage.replaceAll("\\.", "/")); File classFile = new File(url.getFile()); //遍历文件下的所有子文件 加入到容器中 for (File file : classFile.listFiles()) { //如果是文件夹 递归继续遍历，如果不是则将类加入到容器中 if (file.isDirectory()) { //递归扫描 doScanner(scanPackage + "." + file.getName()); } else { //如果不是class文件 则继续跳过循环 if (!file.getName().endsWith(".class")) { continue; } String className = (scanPackage + "." + file.getName()).replace(".class", ""); //将类名作为key 加入到map集合中 mapping.put(className, null); } } } }
3.运行阶段
HfDispatcherServlet
@Override public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { try { doDispatch(req, resp); } catch (Exception e) { resp.getWriter().write("500 Exception " + Arrays.toString(e.getStackTrace())); } } @Override public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws IOException, InvocationTargetException, IllegalAccessException { //请求的url String url = req.getRequestURI(); String contextPath = req.getContextPath(); url = url.replace(contextPath, "").replaceAll("/+", "/"); if (!this.mapping.containsKey(url)) { resp.getWriter().write("404 Not Found!"); return; } Method method = (Method) this.mapping.get(url); Map<String, String[]> params = req.getParameterMap(); method.invoke(this.mapping.get(method.getDeclaringClass().getName()), new Object[]{req, resp, params.get("name")[0]}); }
测试
@HfController @HfRequestMapping("/demo") public class DemoAction { @HfAutowired private IDemoService demoService; @HfRequestMapping("/query.*") public void query(HttpServletRequest req, HttpServletResponse resp, @HfRequestParam("name") String name){ // String result = demoService.get(name); String result = "My name is " + name; try { resp.getWriter().write(result); } catch (IOException e) { e.printStackTrace(); } } }
结果如下: 已经跳转到action中的方法中了。
这个版本很多东西都是写死的，主要为了了解整个扫描包，加入容器管理，初始化bean，请求url根据反射调用action的方法的逻辑。
