前言

前面几篇文章中，我们讲解了Spring MVC执⾏的⼤致原理及关键组件的源码解析，今天，我们来模仿它⼿写⾃⼰的mvc框架。

先梳理一下需要实现的功能点：

tomcat加载配置文件web.xml；
调用web.xml中指定的前端控制器DispatcherServlet加载指定的配置文件（一般为springmvc.xml，本文中的为springmvc.properties）；
扫描相关的类，扫描注解（@Controller，@Service，@RequestMapping，@Autowired）；
IOC容器进行相应Bean初始化以及依赖注入维护；
Spring MVC相关组件的初始化，建立url与method之间的映射关系——HandlerMapping（处理器映射器）；
等待请求进来，处理请求。

实现过程

闲话少说，直接来看代码。

1、注解开发

HardyController：

package com.hardy.edu.mvcframework.annotations;import java.lang.annotation.*;@Documented // 表明这个注解应该被 javadoc 工具记录@Target(ElementType.TYPE)   // 用于设定注解使用范围，ElementType.TYPE标明该注解可用于类或者接口上，用于描述类、接口(包括注解类型) 或enum声明@Retention(RetentionPolicy.RUNTIME) // 指定生存周期，运行时有效public @interface HardyController {String value() default \"\";}

HardyService：

package com.hardy.edu.mvcframework.annotations;import java.lang.annotation.*;@Documented@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)public @interface HardyService {String value() default \"\";}

HardyRequestMapping：

package com.hardy.edu.mvcframework.annotations;import java.lang.annotation.*;@Documented@Target({ElementType.TYPE,ElementType.METHOD})  // 可用于类、接口或方法上@Retention(RetentionPolicy.RUNTIME)public @interface HardyRequestMapping {String value() default \"\";}

HardyAutowired：

package com.hardy.edu.mvcframework.annotations;import java.lang.annotation.*;@Documented@Target(ElementType.FIELD)  // 可用于域上，用于描述域@Retention(RetentionPolicy.RUNTIME)public @inte56crface HardyAutowired {String value() default \"\";}

2、Pojo类Handler

package com.hardy.edu.mvcframework.pojo;import java.lang.reflect.Method;import java.util.HashMap;import java.util.Map;import java.util.regex.Pattern;/*** @author HardyYao* @date 2021/5/13* @description 封装handler方法相关的信息*/public class Handler {private Object controller; // method.invoke(obj,)private Method method;private Pattern pattern; // spring中url是支持正则的private Map<String,Integer> paramIndexMapping; // 参数顺序,是为了进行参数绑定，key是参数名，value代表是第几个参数 此次测试中我们传递的参数那么的map为：<name,2>public Handler(Object controller, Method method, Pattern pattern) {this.controller = controller;this.method = method;this.pattern = pattern;this.paramIndexMapping = new HashMap<>();}public Object getController() {return controller;}public void setController(Object controller) {this.controller = controller;}public Method getMethod() {return method;}public void setMethod(Method method) {this.method = method;}public Pattern getPattern() {return pattern;}public void setPattern(Pattern pattern) {this.pattern = pattern;}public Map<String, Integer> getParamIndexMapping() {return paramIndexMapping;}public void setParamIndexMapping(Map<String, Integer> paramIndexMapping) {this.paramIndexMapping = paramIndexMapping;}}

3、前端控制器实现

package com.hardy.edu.mvcframework.servlet;import com.hardy.edu.mvcframework.annotations.HardyAutowired;import com.hardy.edu.mvcframework.annotations.HardyController;import com.hardy.edu.mvcframework.annotations.HardyRequestMapping;import com.hardy.edu.mvcframework.annotations.HardyService;import com.hardy.edu.mvcframework.pojo.Handler;import org.apache.commons.lang3.StringUtils;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.lang.reflect.Parameter;import java.util.*;import java.util.regex.Matcher;import java.util.regex.Pattern;/*** @author HardyYao* @date 2021/5/13* @description 前端控制器*/public class HardyDispatcherServlet extends HttpServlet {private Properties properties = new Properties();// 缓存扫描到的类的全限定类名private List<String> classNames = new ArrayList<>();// ioc容器private Map<String,Object> ioc = new HashMap<>();// handlerMappingprivate List<Handler> handlerMapping = new ArrayList<>();@Overridepublic void init(ServletConfig config) throws ServletException {// 1 加载配置文件 springmvc.propertiesString contextConfigLocation = config.getInitParameter(\"contextConfigLocation\");doLoadConfig(contextConfigLocation);// 2 扫描相关的类，扫描注解doScan(properties.getProperty(\"scanPackage\"));// 3 初始化bean对象（实现ioc容器，基于注解）doInstance();// 4 实现依赖注入doAutoWired();// 5 构造一个HandlerMapping处理器映射器，将配置好的url和Method建立映射关系initHandlerMapping();System.out.println(\"hardy mvc 初始化完成....\");// 6 等待请求进入，处理请求}/*** 构造一个HandlerMapping处理器映射器* 这是最关键的环节* 目的：将url和method建立关联*/private void initHandlerMapping() {if (ioc.isEmpty()) {return ;}for(Map.Entry<String,Object> entry: ioc.entrySet()) {// 获取ioc中当前遍历的对象的class类型Class<?> aClass = entry.getValue().getClass();if(!aClass.isAnnotationPresent(HardyController.class)) {continue;}String baseUrl = \"\";if(aClass.isAnnotationPresent(HardyRequestMapping.class)) {HardyRequestMapping annotation = aClass.getAnnotation(HardyRequestMapping.class);baseUrl = annotation.value(); // 等同于/demo}// 获取方法Method[] methods = aClass.getMethods();for (int i = 0; i < methods.length; i++) {Method method = methods[i];//  方法没有标识HardyRequestMapping，就不处理if(!method.isAnnotationPresent(HardyRequestMapping.class)) {continue;}// 如果标识，就处理HardyRequestMapping annotation = method.getAnnotation(HardyRequestMapping.class);String methodUrl = annotation.value();  // /queryString url = baseUrl + methodUrl;    // 计算出来的url /demo/query// 把method所有信息及url封装为一个HandlerHandler handler = new Handler(entry.getValue(),method, Pattern.compile(url));// 计算方法的参数位置信息  // query(HttpServletRequest request, HttpServletResponse response,String name)Parameter[] parameters = method.getParameters();for (int j = 0; j < parameters.length; j++) {Parameter parameter = parameters[j];if(parameter.getType() == HttpServletRequest.class || parameter.getType() == HttpServletResponse.class) {// 如果是request和response对象，那么参数名称写HttpServletRequest和HttpServletResponsehandler.getParamIndexMapping().put(parameter.getType().getSimpleName(),j);}else{handler.getParamIndexMapping().put(parameter.getName(),j);  // <name,2>}}// 建立url和method之间的映射关系（map缓存起来）handlerMapping.add(handler);}}}/*** 实现依赖注入*/private void doAutoWired() {// 如果对象为空，则直接返回if (ioc.isEmpty()) {return ;}// 有对象，则进行依赖注入处理// 遍历ioc中所有对象，查看对象中的字段，是否有@HardyAutowired注解，如果有需要维护依赖注入关系for (Map.Entry<String,Object> entry: ioc.entrySet()) {// 获取bean对象中的字段信息Field[] declaredFields = entry.getValue().getClass().getDeclaredFields();// 遍历判断处理for (int i = 0; i < declaredFields.length; i++) {Field declaredField = declaredFields[i];   //  @HardyAutowired  private IDemoService demoService;if (!declaredField.isAnnotationPresent(HardyAutowired.class)) {continue;}// 有该注解HardyAutowired annotation = declaredField.getAnn564otation(HardyAutowired.class);String beanName = annotation.value();  // 需要注入的bean的idif (\"\".equals(beanName.trim())) {// 没有配置具体的bean id，那就需要根据当前字段类型注入（接口注入）  IDemoServicebeanName = declaredField.getType().getName();}// 开启赋值declaredField.setAccessible(true);try {declaredField.set(entry.getValue(), ioc.get(beanName));} catch (IllegalAccessExce56cption e) {e.printStackTrace();}}}}/*** ioc容器：基于classNames缓存的类的全限定类名，以及反射技术，完成对象创建和管理**/private void doInstance()  {if (classNames.size() == 0) {return ;}try{for (int i = 0; i < classNames.size(); i++) {String className =  classNames.get(i);  // com.hardy.demo.controller.DemoController// 反射Class<?> aClass = Class.forName(className);// 区分controller，区分service\'if(aClass.isAnnotationPresent(HardyController.class)) {// controller的id此处不做过多处理，不取value了，就拿类的首字母小写作为id，保存到ioc中String simpleName = aClass.getSimpleName();// DemoControllerString lowerFirstSimpleName = lowerFirst(simpleName); // demoControllerObject o = aClass.newInstance();ioc.put(lowerFirstSimpleName,o);}else if(aClass.isAn1b1cnotationPresent(HardyService.class)) {HardyService annotation = aClass.getAnnotation(HardyService.class);//获取注解value值String beanName = annotation.value();// 如果指定了id，就以指定的为准if(!\"\".equals(beanName.trim())) {ioc.put(beanName,aClass.newInstance());}else{// 如果没有指定，就以类名首字母小写beanName = lowerFirst(aClass.getSimpleName());ioc.put(beanName,aClass.newInstance());}// service层往往是有接口的，面向接口开发，此时再以接口名为id，放入一份对象到ioc中，便于后期根据接口类型注入Class<?>[] interfaces = aClass.getInterfaces();for (int j = 0; j < interfaces.length; j++) {Class<?> anInterface = interfaces[j];// 以接口的全限定类名作为id放入ioc.put(anInterface.getName(),aClass.newInstance());}} else{continue;}}} catch (Exception e) {e.printStackTrace();}}/*** 首字母小写方法* @param str* @return*/public String lowerFirst(String str) {char[] chars = str.toCharArray();if (\'A\' <= chars[0] && chars[0] <= \'Z\') {chars[0] += 32;}return String.valueOf(chars);}/*** 扫描类：scanPackage: com.hardy.demo  package---->  磁盘上的文件夹（File）  com/hardy/demo* @param scanPackage*/private void doScan(String scanPackage) {String scanPackagePath = Thread.currentThread().getContextClassLoader().getResource(\"\").getPath() + scanPackage.replaceAll(\"\\\\.\", \"/\");File pack = new File(scanPackagePath);File[] files = pack.listFiles();if (files != null && files.length > 0) {for (File file: files) {if(file.isDirectory()) { // 子package// 递归doScan(scanPackage + \".\" + file.getName());  // com.hardy.demo.controller}else if(file.getName().endsWith(\".class\")) {String className = scanPackage + \".\" + file.getName().replaceAll(\".class\", \"\");classNames.add(className);}}}}/*** 加载配置文件* @param contextConfigLocation*/private void doLoadConfig(String contextConfigLocation) {InputStream resourceAsStream = this.getClass().getClassLoader().getResourceAsStream(contextConfigLocation);try {properties.load(resourceAsStream);} catch (IOException e) {e.printStackTrace();}}/***  接收处理请求* @param req* @param resp* @throws ServletException* @throws IOException*/@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doPost(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 处理请求：根据url，找到对应的Method方法，进行调用// 获取uri//        String requestURI = req.getRequestURI();//        Method method = handlerMapping.get(requestURI);// 获取到一个反射的方法// 反射调用，需要传入对象，需要传入参数，此处无法完成调用，没有把对象缓存起来，也没有参数！！！！改造initHandlerMapping();//        method.invoke() //// 根据uri获取到能够处理当前请求的hanlder（从handlermapping中（list））Handler handler = getHandler(req);// handler为空则返回：404 not foundif (handler == null) {resp.getWriter().write(\"404 not found\");return;}// 参数绑定// 获取所有参数类型数组，这个数组的长度就是我们最后要传入的args数组的长度Class<?>[] parameterTypes = handler.getMethod().getParameterTypes();// 根据上述数组长度创建一个新的数组（参数数组，是要传入反射调用的）Object[] paraValues = new Object[parameterTypes.length];// 以下就是为了向参数数组中塞值，而且还得保证参数的顺序和方法中形参顺序一致Map<String, String[]> parameterMap = req.getParameterMap();// 遍历request中所有参数  （填充除了request，response之外的参数）for (Map.Entry<String,String[]> param: parameterMap.entrySet()) {// name=1&name=2   name [1,2]String value = StringUtils.join(param.getValue(), \",\");  // 如同 1,2// 如果参数和方法中的参数匹配上了，填充数据if (!handler.getParamIndexMapping().containsKey(param.getKey())) {continue ;}// 方法形参确实有该参数，找到它的索引位置，对应的把参数值放入paraValuesInteger index = handler.getParamIndexMapping().get(param.getKey());//name在第 2 个位置paraValues[index] = value;  // 把前台传递过来的参数值填充到对应的位置去}int requestIndex = handler.getParamIndexMapping().get(HttpServletRequest.class.getSimpleName()); // 0paraValues[requestIndex] = req;int responseIndex = handler.getParamIndexMapping().get(HttpServletResponse.class.getSimpleName()); // 1paraValues[responseIndex] = resp;// 最终调用handler的method属性try {handler.getMethod().invoke(handler.getController(), paraValues);} catch (IllegalAccessException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();}}private Handler getHandler(HttpServletRequest req) {// 为空则直接返回nullif (handlerMapping.isEmpty()) {return null;}String url = req.getRequestURI();// 遍历handlerMappingfor (Handler handler : handlerMapping) {// pattern封装了url，判断其是否匹配urlMatcher matcher = handler.getPattern().matcher(url);// 不匹配则跳过if (!matcher.matches()) {continue;}// 匹配则返回handlerreturn handler;}return null;}}

4、web.xml配置

<!DOCTYPE web-app PUBLIC\"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN\"\"http://java.sun.com/dtd/web-app_2_3.dtd\" ><web-app><display-name>Archetype Created Web Application</display-name><!--  配置servlet  --><servlet><servlet-name>hardymvc</servlet-name><servlet-class>com.hardy.edu.mvcframework.servlet.HardyDispatcherServlet</servlet-class><!-- servlet需要加载的配置文件--><init-param><param-name>contextConfigLocation</param-name><param-value>springmvc.properties</param-value></init-param></servlet><!--  配置映射，拦截所有  --><servlet-mapping>&lad8t;servlet-name>hardymvc</servlet-name><url-pattern>/*</url-pattern></servlet-mapping></web-app>

5、springmvc.properties

scanPackage=com.hardy.demo

调用过程

IDemoService：

package com.hardy.demo.service;/*** @author HardyYao* @date 2021/5/13* @description*/public interface IDemoService {String get(String name);
}

DemoServiceImpl：

package com.hardy.demo.service.impl;import com.hardy.demo.service.IDemoService;import com.hardy.edu.mvcframework.annotations.HardyService;/*** @author HardyYao* @date 2021/5/13* @description*/@HardyService(\"demoService\")public class DemoServiceImpl implements IDemoService {@Overridepublic String get(String name) {System.out.println(\"service 实现类中的name参数：\" + name) ;return name;}}

DemoController：

package com.hardy.demo.controller;import com.hardy.demo.service.IDemoService;import com.hardy.edu.mvcframework.annotations.HardyAutowired;import com.hardy.edu.mvcframework.annotations.HardyController;import com.hardy.edu.mvcframework.annotations.HardyRequestMapping;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/*** @author HardyYao* @date 2021/5/13* @description*/@HardyController@HardyRequestMapping(\"/demo\")public class DemoController {@HardyAutowiredprivate IDemoService demoService;/*** URL: /demo/query?name=zhangsan* @param request* @param response* @param name* @return*/@HardyRequestMapping(\"/query\")public String query(HttpServletRequest request, HttpServletResponse response, String name) {return demoService.get(name);}}

完整的项目结构如下所示：