本文节选自《Spring 5外围原理》
1 自定义配置
1.1 配置application.properties文件
为了解析不便，咱们用application.properties来代替application.xml文件，具体配置内容如下：
scanPackage=com.tom.demo1.2 配置web.xml文件
大家都晓得，所有依赖于Web容器的我的项目都是从读取web.xml文件开始的。咱们先配置好web.xml中的内容：
<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:javaee="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4"> <display-name>Gupao Web Application</display-name> <servlet> <servlet-name>gpmvc</servlet-name> <servlet-class>com.tom.mvcframework.v1.servlet.GPDispatcherServlet</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>gpmvc</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping></web-app>其中的GPDispatcherServlet是模仿Spring实现的外围性能类。
1.3 自定义注解
@GPService注解如下：
package com.tom.mvcframework.annotation;import java.lang.annotation.*;@Target({ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface GPService { String value() default "";}@GPAutowired注解如下：
package com.tom.mvcframework.annotation;import java.lang.annotation.*;@Target({ElementType.FIELD})@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface GPAutowired { String value() default "";}@GPController注解如下：
package com.tom.mvcframework.annotation;import java.lang.annotation.*;@Target({ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface GPController { String value() default "";}@GPRequestMapping注解如下：
package com.tom.mvcframework.annotation;import java.lang.annotation.*;@Target({ElementType.TYPE,ElementType.METHOD})@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface GPRequestMapping { String value() default "";}@GPRequestParam注解如下：
package com.tom.mvcframework.annotation;import java.lang.annotation.*;@Target({ElementType.PARAMETER})@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface GPRequestParam { String value() default "";}1.4 配置注解
配置业务实现类DemoService：
package com.tom.demo.service.impl;import com.tom.demo.service.IDemoService;import com.tom.mvcframework.annotation.GPService;/** * 外围业务逻辑 */@GPServicepublic class DemoService implements IDemoService{ public String get(String name) { return "My name is " + name; }}配置申请入口类DemoAction：
package com.tom.demo.mvc.action;import java.io.IOException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.tom.demo.service.IDemoService;import com.tom.mvcframework.annotation.GPAutowired;import com.tom.mvcframework.annotation.GPController;import com.tom.mvcframework.annotation.GPRequestMapping;import com.tom.mvcframework.annotation.GPRequestParam;@GPController@GPRequestMapping("/demo")public class DemoAction { @GPAutowired private IDemoService demoService; @GPRequestMapping("/query") public void query(HttpServletRequest req, HttpServletResponse resp, @GPRequestParam("name") String name){ String result = demoService.get(name); try { resp.getWriter().write(result); } catch (IOException e) { e.printStackTrace(); } } @GPRequestMapping("/add") public void add(HttpServletRequest req, HttpServletResponse resp, @GPRequestParam("a") Integer a, @GPRequestParam("b") Integer b){ try { resp.getWriter().write(a + "+" + b + "=" + (a + b)); } catch (IOException e) { e.printStackTrace(); } } @GPRequestMapping("/remove") public void remove(HttpServletRequest req,HttpServletResponse resp, @GPRequestParam("id") Integer id){ }}至此，配置全副实现。
2 容器初始化1.0版本
所有的外围逻辑全副写在init()办法中，代码如下：
package com.tom.mvcframework.v1.servlet;import com.tom.mvcframework.annotation.GPAutowired;import com.tom.mvcframework.annotation.GPController;import com.tom.mvcframework.annotation.GPRequestMapping;import com.tom.mvcframework.annotation.GPService;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.Method;import java.net.URL;import java.util.*;public class GPDispatcherServlet extends HttpServlet { private Map<String,Object> mapping = new HashMap<String, Object>(); @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doPost(req,resp);} @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {} @Override public void init(ServletConfig config) throws ServletException { InputStream is = null; try{ Properties configContext = new Properties(); is = this.getClass().getClassLoader().getResourceAsStream(config.getInitParameter ("contextConfigLocation")); configContext.load(is); String scanPackage = configContext.getProperty("scanPackage"); doScanner(scanPackage); for (String className : mapping.keySet()) { if(!className.contains(".")){continue;} Class<?> clazz = Class.forName(className); if(clazz.isAnnotationPresent(GPController.class)){ mapping.put(className,clazz.newInstance()); String baseUrl = ""; if (clazz.isAnnotationPresent(GPRequestMapping.class)) { GPRequestMapping requestMapping = clazz.getAnnotation (GPRequestMapping.class); baseUrl = requestMapping.value(); } Method[] methods = clazz.getMethods(); for (Method method : methods) { if(!method.isAnnotationPresent(GPRequestMapping.class)){ continue; } GPRequestMapping requestMapping = method.getAnnotation (GPRequestMapping.class); String url = (baseUrl + "/" + requestMapping.value()).replaceAll("/+", "/"); mapping.put(url, method); System.out.println("Mapped " + url + "," + method); } }else if(clazz.isAnnotationPresent(GPService.class)){ GPService service = clazz.getAnnotation(GPService.class); String beanName = service.value(); if("".equals(beanName)){beanName = clazz.getName();} Object instance = clazz.newInstance(); mapping.put(beanName,instance); for (Class<?> i : clazz.getInterfaces()) { mapping.put(i.getName(),instance); } }else {continue;} } for (Object object : mapping.values()) { if(object == null){continue;} Class clazz = object.getClass(); if(clazz.isAnnotationPresent(GPController.class)){ Field [] fields = clazz.getDeclaredFields(); for (Field field : fields) { if(!field.isAnnotationPresent(GPAutowired.class)){continue; } GPAutowired autowired = field.getAnnotation(GPAutowired.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 (IllegalAccessException e) { e.printStackTrace(); } } } } } catch (Exception e) { }finally { if(is != null){ try {is.close();} catch (IOException e) { e.printStackTrace(); } } } System.out.print("GP MVC Framework is init"); } private void doScanner(String scanPackage) { URL url = this.getClass().getClassLoader().getResource("/" + scanPackage.replaceAll ("\\.","/")); File classDir = new File(url.getFile()); for (File file : classDir.listFiles()) { if(file.isDirectory()){ doScanner(scanPackage + "." + file.getName());}else { if(!file.getName().endsWith(".class")){continue;} String clazzName = (scanPackage + "." + file.getName().replace(".class","")); mapping.put(clazzName,null); } } }}3 申请执行
重点实现doGet()和doPost()办法，实际上就是在doGet()和doPost()办法中调用doDispatch()办法，具体代码如下：
public class GPDispatcherServlet extends HttpServlet { private Map<String,Object> mapping = new HashMap<String, Object>(); @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doPost(req,resp);} @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { try { doDispatch(req,resp); } catch (Exception e) { resp.getWriter().write("500 Exception " + Arrays.toString(e.getStackTrace())); } } private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception { 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]}); } @Override public void init(ServletConfig config) throws ServletException { ... }}4 优化并实现2.0版本
在1.0版本上进行优化，采纳罕用的设计模式（工厂模式、单例模式、委派模式、策略模式），将init()办法中的代码进行封装。依照之前的实现思路，先搭根底框架，再“填肉注血”，具体代码如下：
//初始化阶段@Overridepublic void init(ServletConfig config) throws ServletException { //1. 加载配置文件 doLoadConfig(config.getInitParameter("contextConfigLocation")); //2. 扫描相干的类 doScanner(contextConfig.getProperty("scanPackage")); //3. 初始化扫描到的类，并且将它们放入IoC容器中 doInstance(); //4. 实现依赖注入 doAutowired(); //5. 初始化HandlerMapping initHandlerMapping(); System.out.println("GP Spring framework is init.");}申明全局成员变量，其中IoC容器就是注册时单例的具体案例：
//保留application.properties配置文件中的内容private Properties contextConfig = new Properties();//保留扫描的所有的类名private List<String> classNames = new ArrayList<String>();//传说中的IoC容器，咱们来揭开它的神秘面纱//为了简化程序，临时不思考ConcurrentHashMap//次要还是关注设计思维和原理private Map<String,Object> ioc = new HashMap<String,Object>();//保留url和Method的对应关系private Map<String,Method> handlerMapping = new HashMap<String,Method>();实现doLoadConfig()办法：
//加载配置文件private void doLoadConfig(String contextConfigLocation) { //间接通过类门路找到Spring主配置文件所在的门路 //并且将其读取进去放到Properties对象中 //相当于将scanPackage=com.tom.demo保留到了内存中 InputStream fis = this.getClass().getClassLoader().getResourceAsStream(contextConfigLocation); try { contextConfig.load(fis); } catch (IOException e) { e.printStackTrace(); }finally { if(null != fis){ try { fis.close(); } catch (IOException e) { e.printStackTrace(); } } }}实现doScanner()办法：
//扫描相干的类private void doScanner(String scanPackage) { //scanPackage = com.tom.demo ，存储的是包门路 //转换为文件门路，实际上就是把.替换为/ URL url = this.getClass().getClassLoader().getResource("/" + scanPackage.replaceAll ("\\.","/")); File classPath = new File(url.getFile()); for (File file : classPath.listFiles()) { if(file.isDirectory()){ doScanner(scanPackage + "." + file.getName()); }else{ if(!file.getName().endsWith(".class")){ continue;} String className = (scanPackage + "." + file.getName().replace(".class","")); classNames.add(className); } }}实现doInstance()办法，doInstance()办法就是工厂模式的具体实现：
private void doInstance() { //初始化，为DI做筹备 if(classNames.isEmpty()){return;} try { for (String className : classNames) { Class<?> clazz = Class.forName(className); //什么样的类才须要初始化呢？ //加了注解的类才初始化，怎么判断？ //为了简化代码逻辑，次要领会设计思维，只用@Controller和@Service举例， //@Componment等就不一一举例了 if(clazz.isAnnotationPresent(GPController.class)){ Object instance = clazz.newInstance(); //Spring默认类名首字母小写 String beanName = toLowerFirstCase(clazz.getSimpleName()); ioc.put(beanName,instance); }else if(clazz.isAnnotationPresent(GPService.class)){ //1. 自定义的beanName GPService service = clazz.getAnnotation(GPService.class); String beanName = service.value(); //2. 默认类名首字母小写 if("".equals(beanName.trim())){ beanName = toLowerFirstCase(clazz.getSimpleName()); } Object instance = clazz.newInstance(); ioc.put(beanName,instance); //3. 依据类型主动赋值，这是投机取巧的形式 for (Class<?> i : clazz.getInterfaces()) { if(ioc.containsKey(i.getName())){ throw new Exception("The “" + i.getName() + "” is exists!!"); } //把接口的类型间接当成key ioc.put(i.getName(),instance); } }else { continue; } } }catch (Exception e){ e.printStackTrace(); }}为了解决不便，本人实现了toLowerFirstCase()办法，来实现类名首字母小写，具体代码如下：
//将类名首字母改为小写private String toLowerFirstCase(String simpleName) { char [] chars = simpleName.toCharArray(); //之所以要做加法，是因为大、小写字母的ASCII码相差32 //而且大写字母的ASCII码要小于小写字母的ASCII码 //在Java中，对char做算术运算实际上就是对ASCII码做算术运算 chars[0] += 32; return String.valueOf(chars);}实现doAutowired()办法：
//主动进行依赖注入private void doAutowired() { if(ioc.isEmpty()){return;} for (Map.Entry<String, Object> entry : ioc.entrySet()) { //获取所有的字段，包含private、protected、default类型的 //失常来说，一般的OOP编程只能取得public类型的字段 Field[] fields = entry.getValue().getClass().getDeclaredFields(); for (Field field : fields) { if(!field.isAnnotationPresent(GPAutowired.class)){continue;} GPAutowired autowired = field.getAnnotation(GPAutowired.class); //如果用户没有自定义beanName，默认就依据类型注入 //这个中央省去了对类名首字母小写的状况的判断，这个作为课后作业请“小伙伴们”本人去实现 String beanName = autowired.value().trim(); if("".equals(beanName)){ //取得接口的类型，作为key，稍后用这个key到IoC容器中取值 beanName = field.getType().getName(); } //如果是public以外的类型，只有加了@Autowired注解都要强制赋值 //反射中叫作暴力拜访 field.setAccessible(true); try { //用反射机制动静给字段赋值 field.set(entry.getValue(),ioc.get(beanName)); } catch (IllegalAccessException e) { e.printStackTrace(); } } }}实现initHandlerMapping()办法，HandlerMapping就是策略模式的利用案例：
//初始化url和Method的一对一关系private void initHandlerMapping() { if(ioc.isEmpty()){ return; } for (Map.Entry<String, Object> entry : ioc.entrySet()) { Class<?> clazz = entry.getValue().getClass(); if(!clazz.isAnnotationPresent(GPController.class)){continue;} //保留写在类下面的@GPRequestMapping("/demo") String baseUrl = ""; if(clazz.isAnnotationPresent(GPRequestMapping.class)){ GPRequestMapping requestMapping = clazz.getAnnotation(GPRequestMapping.class); baseUrl = requestMapping.value(); } //默认获取所有的public类型的办法 for (Method method : clazz.getMethods()) { if(!method.isAnnotationPresent(GPRequestMapping.class)){continue;} GPRequestMapping requestMapping = method.getAnnotation(GPRequestMapping.class); //优化 String url = ("/" + baseUrl + "/" + requestMapping.value()) .replaceAll("/+","/"); handlerMapping.put(url,method); System.out.println("Mapped :" + url + "," + method); } }}到这里初始化的工作实现，接下来实现运行的逻辑，来看doGet()和doPost()办法的代码：
@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doPost(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //运行阶段 try { doDispatch(req,resp); } catch (Exception e) { e.printStackTrace(); resp.getWriter().write("500 Exection,Detail : " + Arrays.toString(e.getStackTrace())); }}doPost()办法中用了委派模式，委派模式的具体逻辑在doDispatch()办法中实现：
private void doDispatch(HttpServletRequest req, HttpServletResponse resp)throws Exception { String url = req.getRequestURI(); String contextPath = req.getContextPath(); url = url.replaceAll(contextPath,"").replaceAll("/+","/"); if(!this.handlerMapping.containsKey(url)){ resp.getWriter().write("404 Not Found!!"); return; } Method method = this.handlerMapping.get(url); //第一个参数：办法所在的实例 //第二个参数：调用时所须要的实参 Map<String,String[]> params = req.getParameterMap(); //投机取巧的形式 String beanName = toLowerFirstCase(method.getDeclaringClass().getSimpleName()); method.invoke(ioc.get(beanName),new Object[]{req,resp,params.get("name")[0]}); //System.out.println(method);}在以上代码中，doDispatch()尽管实现了动静委派并进行了反射调用，但对url参数的解决还是动态的。要实现url参数的动静获取，其实有些简单。咱们能够优化doDispatch()办法的实现，代码如下：
private void doDispatch(HttpServletRequest req, HttpServletResponse resp)throws Exception { String url = req.getRequestURI(); String contextPath = req.getContextPath(); url = url.replaceAll(contextPath,"").replaceAll("/+","/"); if(!this.handlerMapping.containsKey(url)){ resp.getWriter().write("404 Not Found!!"); return; } Method method = this.handlerMapping.get(url); //第一个参数：办法所在的实例 //第二个参数：调用时所须要的实参 Map<String,String[]> params = req.getParameterMap(); //获取办法的形参列表 Class<?> [] parameterTypes = method.getParameterTypes(); //保留申请的url参数列表 Map<String,String[]> parameterMap = req.getParameterMap(); //保留赋值参数的地位 Object [] paramValues = new Object[parameterTypes.length]; //依据参数地位动静赋值 for (int i = 0; i < parameterTypes.length; i ++){ Class parameterType = parameterTypes[i]; if(parameterType == HttpServletRequest.class){ paramValues[i] = req; continue; }else if(parameterType == HttpServletResponse.class){ paramValues[i] = resp; continue; }else if(parameterType == String.class){ //提取办法中加了注解的参数 Annotation[] [] pa = method.getParameterAnnotations(); for (int j = 0; j < pa.length ; j ++) { for(Annotation a : pa[i]){ if(a instanceof GPRequestParam){ String paramName = ((GPRequestParam) a).value(); if(!"".equals(paramName.trim())){ String value = Arrays.toString(parameterMap.get(paramName)) .replaceAll("\\[|\\]","") .replaceAll("\\s",","); paramValues[i] = value; } } } } } } //投机取巧的形式 //通过反射取得Method所在的Class，取得Class之后还要取得Class的名称 //再调用toLowerFirstCase取得beanName String beanName = toLowerFirstCase(method.getDeclaringClass().getSimpleName()); method.invoke(ioc.get(beanName),new Object[]{req,resp,params.get("name")[0]});}关注微信公众号『 Tom弹架构 』回复“Spring”可获取残缺源码。
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