30个类手写Spring核心原理之MVC映射功能（4）

本文节选自《Spring 5核心原理》

接下来我们来完成MVC模块的功能，应该不需要再做说明。Spring MVC的入口就是从DispatcherServlet开始的，而前面的章节中已完成了web.xml的基础配置。下面就从DispatcherServlet开始添砖加瓦。

1 MVC顶层设计

1.1 GPDispatcherServlet

我们已经了解到Servlet的生命周期由init()到service()再到destory()组成，destory()方法我们不做实现。前面我们讲过，这是J2EE中模板模式的典型应用。下面先定义好全局变量：

package com.tom.spring.formework.webmvc.servlet;import com.tom.spring.formework.annotation.GPController;import com.tom.spring.formework.annotation.GPRequestMapping;import com.tom.spring.formework.context.GPApplicationContext;import com.tom.spring.formework.webmvc.*;import lombok.extern.slf4j.Slf4j;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.lang.reflect.Method;import java.util.*;import java.util.regex.Matcher;import java.util.regex.Pattern;//Servlet只是作为一个MVC的启动入口@Slf4jpublic class GPDispatcherServlet extends HttpServlet {private  final String LOCATION = "contextConfigLocation";//读者可以思考一下这样设计的经典之处//GPHandlerMapping最核心的设计，也是最经典的//它直接干掉了Struts、Webwork等MVC框架private List<GPHandlerMapping> handlerMappings = new ArrayList<GPHandlerMapping>();private Map<GPHandlerMapping,GPHandlerAdapter> handlerAdapters = new HashMap<GPHandlerMapping, GPHandlerAdapter>();private List<GPViewResolver> viewResolvers = new ArrayList<GPViewResolver>();private GPApplicationContext context;}下面实现init()方法，我们主要完成IoC容器的初始化和Spring MVC九大组件的初始化。@Overridepublic void init(ServletConfig config) throws ServletException {//相当于把IoC容器初始化了context = new GPApplicationContext(config.getInitParameter(LOCATION));initStrategies(context);}protected void initStrategies(GPApplicationContext context) {//有九种策略//针对每个用户请求，都会经过一些处理策略处理，最终才能有结果输出//每种策略可以自定义干预，但是最终的结果都一致// =============  这里说的就是传说中的九大组件 ================initMultipartResolver(context);//文件上传解析，如果请求类型是multipart，将通过MultipartResolver进行文件上传解析initLocaleResolver(context);//本地化解析initThemeResolver(context);//主题解析/** 我们自己会实现 *///GPHandlerMapping 用来保存Controller中配置的RequestMapping和Method的对应关系initHandlerMappings(context);//通过HandlerMapping将请求映射到处理器/** 我们自己会实现 *///HandlerAdapters 用来动态匹配Method参数，包括类转换、动态赋值initHandlerAdapters(context);//通过HandlerAdapter进行多类型的参数动态匹配initHandlerExceptionResolvers(context);//如果执行过程中遇到异常，将交给HandlerExceptionResolver来解析initRequestToViewNameTranslator(context);//直接将请求解析到视图名/** 我们自己会实现 *///通过ViewResolvers实现动态模板的解析//自己解析一套模板语言initViewResolvers(context);//通过viewResolver将逻辑视图解析到具体视图实现initFlashMapManager(context);//Flash映射管理器}private void initFlashMapManager(GPApplicationContext context) {}private void initRequestToViewNameTranslator(GPApplicationContext context) {}private void initHandlerExceptionResolvers(GPApplicationContext context) {}private void initThemeResolver(GPApplicationContext context) {}private void initLocaleResolver(GPApplicationContext context) {}private void initMultipartResolver(GPApplicationContext context) {}//将Controller中配置的RequestMapping和Method进行一一对应private void initHandlerMappings(GPApplicationContext context) {//按照我们通常的理解应该是一个Map//Map<String,Method> map;//map.put(url,Method)//首先从容器中获取所有的实例String [] beanNames = context.getBeanDefinitionNames();try {for (String beanName : beanNames) {//到了MVC层，对外提供的方法只有一个getBean()方法//返回的对象不是BeanWrapper，怎么办？Object controller = context.getBean(beanName);//Object controller = GPAopUtils.getTargetObject(proxy);Class<?> clazz = controller.getClass();if (!clazz.isAnnotationPresent(GPController.class)) {continue;}String baseUrl = "";if (clazz.isAnnotationPresent(GPRequestMapping.class)) {GPRequestMapping requestMapping = clazz.getAnnotation(GPRequestMapping.class);baseUrl = requestMapping.value();}//扫描所有的public类型的方法Method[] methods = clazz.getMethods();for (Method method : methods) {if (!method.isAnnotationPresent(GPRequestMapping.class)) {continue;}GPRequestMapping requestMapping = method.getAnnotation(GPRequestMapping.class);String regex = ("/" + baseUrl + requestMapping.value().replaceAll("\\\\*", ".*")).replaceAll("/+", "/");Pattern pattern = Pattern.compile(regex);this.handlerMappings.add(new GPHandlerMapping(pattern, controller, method));log.info("Mapping: " + regex + " , " + method);}}}catch (Exception e){e.printStackTrace();}}private void initHandlerAdapters(GPApplicationContext context) {//在初始化阶段，我们能做的就是，将这些参数的名字或者类型按一定的顺序保存下来//因为后面用反射调用的时候，传的形参是一个数组//可以通过记录这些参数的位置index，逐个从数组中取值，这样就和参数的顺序无关了for (GPHandlerMapping handlerMapping : this.handlerMappings){//每个方法有一个参数列表，这里保存的是形参列表this.handlerAdapters.put(handlerMapping,new GPHandlerAdapter());}}private void initViewResolvers(GPApplicationContext context) {//在页面中输入http://localhost/first.html//解决页面名字和模板文件关联的问题String templateRoot = context.getConfig().getProperty("templateRoot");String templateRootPath = this.getClass().getClassLoader().getResource (templateRoot).getFile();File templateRootDir = new File(templateRootPath);for (File template : templateRootDir.listFiles()) {this.viewResolvers.add(new GPViewResolver(templateRoot));}}

在上面的代码中，我们只实现了九大组件中的三大核心组件的基本功能，分别是HandlerMapping、HandlerAdapter、ViewResolver，完成MVC最核心的调度功能。其中HandlerMapping就是策略模式的应用，用输入URL间接调用不同的Method已达到获取结果的目的。顾名思义，HandlerAdapter应用的是适配器模式，将Request的字符型参数自动适配为Method的Java实参，主要实现参数列表自动适配和类型转换功能。ViewResolver也算一种策略，根据不同的请求选择不同的模板引擎来进行页面的渲染。接下来看service()方法，它主要负责接收请求，得到Request和Response对象。在Servlet子类中service()方法被拆分成doGet()方法和doPost()方法。我们在doGet()方法中直接调用doPost()方法，在doPost()方法中调用doDispatch()方法，真正的调用逻辑由doDispatch()来执行。

@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doPost(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {try {doDispatch(req, resp);}catch (Exception e){resp.getWriter().write("<font size=\'25\' color=\'blue\'>500 Exception</font><br/>Details: <br/>" + Arrays.toString(e.getStackTrace()).replaceAll("\\\\[|\\\\]","").replaceAll("\\\\s","\\r\\n") +  "<font color=\'green\'><i>Copyright@GupaoEDU </i></font>");e.printStackTrace();}}private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception{//根据用户请求的URL来获得一个HandlerGPHandlerMapping handler = getHandler(req);if(handler == null){processDispatchResult(req,resp,new GPModelAndView("404"));return;}GPHandlerAdapter ha = getHandlerAdapter(handler);//这一步只是调用方法，得到返回值GPModelAndView mv = ha.handle(req, resp, handler);//这一步才是真的输出processDispatchResult(req,resp, mv);}private void processDispatchResult(HttpServletRequest request,HttpServletResponse response, GPModelAndView mv) throws Exception {//调用viewResolver的resolveViewName()方法if(null == mv){ return;}if(this.viewResolvers.isEmpty()){ return;}if (this.viewResolvers != null) {for (GPViewResolver viewResolver : this.viewResolvers) {GPView view = viewResolver.resolveViewName(mv.getViewName(), null);if (view != null) {view.render(mv.getModel(),request,response);return;}}}}private GPHandlerAdapter getHandlerAdapter(GPHandlerMapping handler) {if(this.handlerAdapters.isEmpty()){return  null;}GPHandlerAdapter ha = this.handlerAdapters.get(handler);if (ha.supports(handler)) {return ha;}return null;}private GPHandlerMapping getHandler(HttpServletRequest req) {if(this.handlerMappings.isEmpty()){ return  null;}String url = req.getRequestURI();String contextPath = req.getContextPath();url = url.replace(contextPath,"").replaceAll("/+","/");for (GPHandlerMapping handler : this.handlerMappings) {Matcher matcher = handler.getPattern().matcher(url);if(!matcher.matches()){ continue;}return handler;}return null;}

GPDisptcherServlet的完整代码请关注微信公众号回复“Spring”。下面补充实现上面的代码中缺失的依赖类。

1.2 GPHandlerMapping

我们已经知道HandlerMapping主要用来保存URL和Method的对应关系，这里其实使用的是策略模式。

package com.tom.spring.formework.webmvc;import java.lang.reflect.Method;import java.util.regex.Pattern;public class GPHandlerMapping {private Object controller; //目标方法所在的contrller对象private Method method; //URL对应的目标方法private Pattern pattern;  //URL的封装public GPHandlerMapping(Pattern pattern,Object controller, Method method) {this.controller = controller;this.method = method;this.pattern = pattern;}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;}}

1.3 GPHandlerAdapter

原生Spring的HandlerAdapter主要完成请求传递到服务端的参数列表与Method实参列表的对应关系，完成参数值的类型转换工作。核心方法是handle()，在handle()方法中用反射来调用被适配的目标方法，并将转换包装好的参数列表传递过去。

package com.tom.spring.formework.webmvc;import com.tom.spring.formework.annotation.GPRequestParam;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.lang.annotation.Annotation;import java.util.Arrays;import java.util.HashMap;import java.util.Map;//专人干专事public class GPHandlerAdapter {public boolean supports(Object handler){return (handler instanceof GPHandlerMapping);}public GPModelAndView handle(HttpServletRequest req, HttpServletResponse resp, Object handler) throws Exception{GPHandlerMapping handlerMapping = (GPHandlerMapping)handler;//每个方法有一个参数列表，这里保存的是形参列表Map<String,Integer> paramMapping = new HashMap<String, Integer>();//这里只是给出命名参数Annotation[][] pa = handlerMapping.getMethod().getParameterAnnotations();for (int i = 0; i < pa.length ; i ++) {for (Annotation a : pa[i]) {if(a instanceof GPRequestParam){String paramName = ((GPRequestParam) a).value();if(!"".equals(paramName.trim())){paramMapping.put(paramName,i);}}}}//根据用户请求的参数信息，跟Method中的参数信息进行动态匹配//resp 传进来的目的只有一个：将其赋值给方法参数，仅此而已//只有当用户传过来的ModelAndView为空的时候，才会新建一个默认的//1. 要准备好这个方法的形参列表//方法重载时形参的决定因素：参数的个数、参数的类型、参数顺序、方法的名字//只处理Request和ResponseClass<?>[] paramTypes = handlerMapping.getMethod().getParameterTypes();for (int i = 0;i < paramTypes.length; i ++) {Class<?> type = paramTypes[i];if(type == HttpServletRequest.class ||type == HttpServletResponse.class){paramMapping.put(type.getName(),i);}}//2. 得到自定义命名参数所在的位置//用户通过URL传过来的参数列表Map<String,String[]> reqParameterMap = req.getParameterMap();//3. 构造实参列表Object [] paramValues = new Object[paramTypes.length];for (Map.Entry<String,String[]> param : reqParameterMap.entrySet()) {String value = Arrays.toString(param.getValue()).replaceAll("\\\\[|\\\\]",""). replaceAll("\\\\s","");if(!paramMapping.containsKey(param.getKey())){continue;}int index = paramMapping.get(param.getKey());//因为页面传过来的值都是String类型的，而在方法中定义的类型是千变万化的//所以要针对我们传过来的参数进行类型转换paramValues[index] = caseStringValue(value,paramTypes[index]);}if(paramMapping.containsKey(HttpServletRequest.class.getName())) {int reqIndex = paramMapping.get(HttpServletRequest.class.getName());paramValues[reqIndex] = req;}if(paramMapping.containsKey(HttpServletResponse.class.getName())) {int respIndex = paramMapping.get(HttpServletResponse.class.getName());paramValues[respIndex] = resp;}//4. 从handler中取出Controller、Method，然后利用反射机制进行调用Object result = handlerMapping.getMethod().invoke(handlerMapping.getController(), paramValues);if(result == null){ return  null; }boolean isModelAndView = handlerMapping.getMethod().getReturnType() == GPModelAndView.class;if(isModelAndView){return (GPModelAndView)result;}else{return null;}}private Object caseStringValue(String value,Class<?> clazz){if(clazz == String.class){return value;}else if(clazz == Integer.class){return  Integer.valueOf(value);}else if(clazz == int.class){return Integer.valueOf(value).intValue();}else {return null;}}}

1.4 GPModelAndView

原生Spring中ModelAndView类主要用于封装页面模板和要往页面传送的参数的对应关系。

package com.tom.spring.formework.webmvc;import java.util.Map;public class GPModelAndView {private String viewName; //页面模板的名称private Map<String,?> model; //往页面传送的参数public GPModelAndView(String viewName) {this(viewName,null);}public GPModelAndView(String viewName, Map<String, ?> model) {this.viewName = viewName;this.model = model;}public String getViewName() {return viewName;}public void setViewName(String viewName) {this.viewName = viewName;}public Map<String, ?> getModel() {return model;}public void setModel(Map<String, ?> model) {this.model = model;}}

1.5 GPViewResolver

原生Spring中的ViewResolver主要完成模板名称和模板解析引擎的匹配。通过在Serlvet中调用resolveViewName()方法来获得模板所对应的View。在这个Mini版本中简化了实现，只实现了一套默认的模板引擎，语法也是完全自定义的。

package com.tom.spring.formework.webmvc;import java.io.File;import java.util.Locale;//设计这个类的主要目的是：//1. 将一个静态文件变为一个动态文件//2. 根据用户传送不同的参数，产生不同的结果//最终输出字符串，交给Response输出public class GPViewResolver {private final String DEFAULT_TEMPLATE_SUFFIX = ".html";private File templateRootDir;private String viewName;public GPViewResolver(String templateRoot){String templateRootPath = this.getClass().getClassLoader().getResource(templateRoot). getFile();this.templateRootDir = new File(templateRootPath);}public GPView resolveViewName(String viewName, Locale locale) throws Exception {this.viewName = viewName;if(null == viewName || "".equals(viewName.trim())){ return null;}viewName = viewName.endsWith(DEFAULT_TEMPLATE_SUFFIX) ? viewName : (viewName + DEFAULT_TEMPLATE_SUFFIX);File templateFile = new File((templateRootDir.getPath() + "/" + viewName).replaceAll ("/+", "/"));return new GPView(templateFile);}public String getViewName() {return viewName;}}

1.6 GPView

这里的GPView就是前面所说的自定义模板解析引擎，其核心方法是render()。在render()方法中完成对模板的渲染，最终返回浏览器能识别的字符串，通过Response输出。

package com.tom.spring.formework.webmvc;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.RandomAccessFile;import java.util.Map;import java.io.File;import java.util.regex.Matcher;import java.util.regex.Pattern;public class GPView {public static final String DEFAULT_CONTENT_TYPE = "text/html;charset=utf-8";private File viewFile;public GPView(File viewFile){this.viewFile = viewFile;}public String getContentType(){return DEFAULT_CONTENT_TYPE;}public void render(Map<String, ?> model,HttpServletRequest request, HttpServletResponse response) throws Exception{StringBuffer sb = new StringBuffer();RandomAccessFile ra = new RandomAccessFile(this.viewFile,"r");try {String line = null;while (null != (line = ra.readLine())) {line = new String(line.getBytes("ISO-8859-1"),"utf-8");Pattern pattern = Pattern.compile("￥\\\\{[^\\\\}]+\\\\}",Pattern.CASE_INSENSITIVE);Matcher matcher = pattern.matcher(line);while (matcher.find()) {String paramName = matcher.group();paramName = paramName.replaceAll("￥\\\\{|\\\\}","");Object paramValue = model.get(paramName);if (null == paramValue) { continue; }//要把￥{}中间的这个字符串取出来line = matcher.replaceFirst(makeStringForRegExp(paramValue.toString()));matcher = pattern.matcher(line);}sb.append(line);}}finally {ra.close();}response.setCharacterEncoding("utf-8");//response.setContentType(DEFAULT_CONTENT_TYPE);response.getWriter().write(sb.toString());}//处理特殊字符public static String makeStringForRegExp(String str) {return str.replace("\\\\", "\\\\\\\\").replace("*", "\\\\*").replace("+", "\\\\+").replace("|", "\\\\|").replace("{", "\\\\{").replace("}", "\\\\}").replace("(", "\\\\(").replace(")", "\\\\)").replace("^", "\\\\^").replace("$", "\\\\$").replace("[", "\\\\[").replace("]", "\\\\]").replace("?", "\\\\?").replace(",", "\\\\,").replace(".", "\\\\.").replace("&", "\\\\&");}}

从上面的代码可以看出，GPView是基于HTML文件来对页面进行渲染的。但是加入了一些自定义语法，例如在模板页面中扫描到￥这样的表达式，就会从ModelAndView的Model中找到name所对应的值，并且用正则表达式将其替换（外国人喜欢用美元符号$，我们的模板引擎就用人民币符号￥）。

2 业务代码实现

2.1 IQueryService

定义一个负责查询业务的顶层接口IQueryService，提供一个query()方法：

package com.tom.spring.demo.service;/*** 查询业务**/public interface IQueryService  {/*** 查询*/public String query(String name);}

2.2 QueryService

查询业务的实现QueryService也非常简单，就是打印一下调用时间和传入的参数，并封装为JSON格式返回：

package com.tom.spring.demo.service.impl;import java.text.SimpleDateFormat;import java.util.Date;import com.tom.spring.demo.service.IQueryService;import com.tom.spring.formework.annotation.GPService;import lombok.extern.slf4j.Slf4j;/*** 查询业务**/@GPService@Slf4jpublic class QueryService implements IQueryService {/*** 查询*/public String query(String name) {SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");String time = sdf.format(new Date());String json = "{name:\\"" + name + "\\",time:\\"" + time + "\\"}";log.info("这是在业务方法中打印的：" + json);return json;}}

2.3 IModifyService

定义一个增、删、改业务的顶层接口IModifyService：

package com.tom.spring.demo.service;/*** 增、删、改业务*/public interface IModifyService {/*** 增加*/public String add(String name, String addr) ;/*** 修改*/public String edit(Integer id, String name);/*** 删除*/public String remove(Integer id);}

2.4 ModifyService

增、删、改业务的实现ModifyService也非常简单，主要是打印传过来的参数：

package com.tom.spring.demo.service.impl;import com.tom.spring.demo.service.IModifyService;import com.tom.spring.formework.annotation.GPService;/*** 增、删、改业务*/@GPServicepublic class ModifyService implements IModifyService {/*** 增加*/public String add(String name,String addr) {return "modifyService add,name=" + name + ",addr=" + addr;}/*** 修改*/public String edit(Integer id,String name) {return "modifyService edit,id=" + id + ",name=" + name;}/*** 删除*/public String remove(Integer id) {return "modifyService id=" + id;}}

2.5 MyAction

Controller的主要功能是负责调度，不做业务实现。业务实现方法全部在Service层，一般我们会将Service实例注入Controller。MyAction中主要实现对IQueryService和IModifyService的调度，统一返回结果：

package com.tom.spring.demo.action;import java.io.IOException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.tom.spring.demo.service.IModifyService;import com.tom.spring.demo.service.IQueryService;import com.tom.spring.formework.annotation.GPAutowired;import com.tom.spring.formework.annotation.GPController;import com.tom.spring.formework.annotation.GPRequestMapping;import com.tom.spring.formework.annotation.GPRequestParam;import com.tom.spring.formework.webmvc.GPModelAndView;/*** 公布接口URL*/@GPController@GPRequestMapping("/web")public class MyAction {@GPAutowired IQueryService queryService;@GPAutowired IModifyService modifyService;@GPRequestMapping("/query.json")public GPModelAndView query(HttpServletRequest request, HttpServletResponse response,@GPRequestParam("name") String name){String result = queryService.query(name);return out(response,result);}@GPRequestMapping("/add*.json")public GPModelAndView add(HttpServletRequest request,HttpServletResponse response,@GPRequestParam("name") String name,@GPRequestParam("addr") String addr){String result = modifyService.add(name,addr);return out(response,result);}@GPRequestMapping("/remove.json")public GPModelAndView remove(HttpServletRequest request,HttpServletResponse response,@GPRequestParam("id") Integer id){String result = modifyService.remove(id);return out(response,result);}@GPRequestMapping("/edit.json")public GPModelAndView edit(HttpServletRequest request,HttpServletResponse response,@GPRequestParam("id") Integer id,@GPRequestParam("name") String name){String result = modifyService.edit(id,name);return out(response,result);}private GPModelAndView out(HttpServletResponse resp,String str){try {resp.getWriter().write(str);} catch (IOException e) {e.printStackTrace();}return null;}}

2.6 PageAction

专门设计PageAction是为了演示Mini版Spring对模板引擎的支持，实现从Controller层到View层的传参，以及对模板的渲染进行最终输出：

package com.tom.spring.demo.action;import java.util.HashMap;import java.util.Map;import com.tom.spring.demo.service.IQueryService;import com.tom.spring.formework.annotation.GPAutowired;import com.tom.spring.formework.annotation.GPController;import com.tom.spring.formework.annotation.GPRequestMapping;import com.tom.spring.formework.annotation.GPRequestParam;import com.tom.spring.formework.webmvc.GPModelAndView;/*** 公布接口URL*/@GPController@GPRequestMapping("/")public class PageAction {@GPAutowired IQueryService queryService;@GPRequestMapping("/first.html")public GPModelAndView query(@GPRequestParam("teacher") String teacher){String result = queryService.query(teacher);Map<String,Object> model = new HashMap<String,Object>();model.put("teacher", teacher);model.put("data", result);model.put("token", "123456");return new GPModelAndView("first.html",model);}}

3 定制模板页面

为了更全面地演示页面渲染效果，分别定义了first.html对应PageAction中的first.html请求、404.html默认页和500.html异常默认页。

3.1 first.html

first.html定义如下：

<!DOCTYPE html><html lang="zh-cn"><head><meta charset="utf-8"><title>SpringMVC模板引擎演示</title></head><center><h1>大家好，我是￥{teacher}老师<br/>欢迎大家一起来探索Spring的世界</h1><h3>Hello,My name is ￥{teacher}</h3><div>￥{data}</div>Token值：￥{token}</center></html>

3.2 404.html

404.html定义如下：

<!DOCTYPE html><html lang="zh-cn"><head><meta charset="utf-8"><title>页面去火星了</title></head><body><font size=\'25\' color=\'red\'>404 Not Found</font><br/><font color=\'green\'><i>Copyright @GupaoEDU</i></font></body></html>

3.3 500.html

500.html定义如下：

<!DOCTYPE html><html lang="zh-cn"><head><meta charset="utf-8"><title>服务器好像累了</title></head><body><font size=\'25\' color=\'blue\'>500 服务器好像有点累了，需要休息一下</font><br/><b>Message:￥{detail}</b><br/><b>StackTrace:￥{stackTrace}</b><br/><font color=\'green\'><i>Copyright@GupaoEDU</i></font></body></html>