装逼必备！手写springMVC（附详解）

mac2024-05-22 29

之前提到过的ssm流程原理今天就从底层解开ssm的面纱首先准备几个常用的annotation（也就是注解）： 1.Hcontroller（controller）

package annotation; import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; @Target(ElementType.TYPE)//表示注解运行在哪里 @Retention(RetentionPolicy.RUNTIME)//用来说明该注解类的生命周期 @Documented public @interface HController { /** * 表示给controller注册别名 * @author hxz * @return */ String value() default ""; }

2.HRequestMapping(RequestMapping)

package annotation; import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; @Target({ElementType.TYPE,ElementType.METHOD})//表示注解运行在哪里 @Retention(RetentionPolicy.RUNTIME)//用来说明该注解类的生命周期 @Documented public @interface HRequestMapping { /** * 表示访问该方法的url * @author hxz * @return */ String value() default ""; }

3.HRequestParam(RequestParam)

package annotation; import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; @Target({ElementType.TYPE,ElementType.METHOD})//表示注解运行在哪里 @Retention(RetentionPolicy.RUNTIME)//用来说明该注解类的生命周期 @Documented public @interface HRequestMapping { /** * 表示访问该方法的url * @author hxz * @return */ String value() default ""; }

这里只用了三个，当然还有很多，这里不祥解最重要的！最重要的！最重要的！ MyDispatcherServlet（spring MVC核心DispatcherServlet）

package servlet; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.lang.reflect.Method; import java.net.URL; import java.util.ArrayList; import java.util.Arrays; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.Properties; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import annotation.HController; import annotation.HRequestMapping; public class MyDispatcherServlet extends HttpServlet{ private Properties properties = new Properties(); private List<String> classNames = new ArrayList<String>(); private Map<String, Object> ioc = new HashMap<String, Object>(); private Map<String, Method> handlerMapping = new HashMap<String, Method>(); private Map<String, Object> controllerMap =new HashMap<String, Object>(); @Override public void init(ServletConfig config) throws ServletException { //1.加载配置文件 doLoadConfig(config.getInitParameter("contextConfigLocation")); //2.初始化所有相关联的类,扫描用户设定的包下面所有的类 doScanner(properties.getProperty("scanPackage")); //3.拿到扫描到的类,通过反射机制,实例化,并且放到ioc容器中(k-v beanName-bean) beanName默认是首字母小写 doInstance(); //4.初始化HandlerMapping(将url和method对应上) initHandlerMapping(); } @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 { //处理请求 doDispatch(req,resp); } catch (Exception e) { resp.getWriter().write("500!! Server Exception"); } } private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception { if(handlerMapping.isEmpty()){ return; } String url =req.getRequestURI(); String contextPath = req.getContextPath(); url=url.replace(contextPath, "").replaceAll("/+", "/"); if(!this.handlerMapping.containsKey(url)){ resp.getWriter().write("404 NOT FOUND!"); return; } Method method =this.handlerMapping.get(url); //获取方法的参数列表 Class<?>[] parameterTypes = method.getParameterTypes(); //获取请求的参数 Map<String, String[]> parameterMap = req.getParameterMap(); //保存参数值 Object [] paramValues= new Object[parameterTypes.length]; //方法的参数列表 for (int i = 0; i<parameterTypes.length; i++){ //根据参数名称，做某些处理 String requestParam = parameterTypes[i].getSimpleName(); if (requestParam.equals("HttpServletRequest")){ //参数类型已明确，这边强转类型 paramValues[i]=req; continue; } if (requestParam.equals("HttpServletResponse")){ paramValues[i]=resp; continue; } if(requestParam.equals("String")){ for (Entry<String, String[]> param : parameterMap.entrySet()) { String value =Arrays.toString(param.getValue()).replaceAll("\\[|\\]", "").replaceAll(",\\s", ","); paramValues[i]=value; } } } //利用反射机制来调用 try { method.invoke(this.controllerMap.get(url), paramValues);//第一个参数是method所对应的实例在ioc容器中 } catch (Exception e) { e.printStackTrace(); } } private void doLoadConfig(String location){ //把web.xml中的contextConfigLocation对应value值的文件加载到流里面 InputStream resourceAsStream = this.getClass().getClassLoader().getResourceAsStream(location); try { //用Properties文件加载文件里的内容 properties.load(resourceAsStream); } catch (IOException e) { e.printStackTrace(); }finally { //关流 if(null!=resourceAsStream){ try { resourceAsStream.close(); } catch (IOException e) { e.printStackTrace(); } } } } private void doScanner(String packageName) { //把所有的.替换成/ URL url =this.getClass().getClassLoader().getResource("/"+packageName.replaceAll("\\.", "/")); File dir = new File(url.getFile()); for (File file : dir.listFiles()) { if(file.isDirectory()){ //递归读取包 doScanner(packageName+"."+file.getName()); }else{ String className =packageName +"." +file.getName().replace(".class", ""); classNames.add(className); } } } private void doInstance() { if (classNames.isEmpty()) { return; } for (String className : classNames) { try { //把类搞出来,反射来实例化(只有加@MyController需要实例化) Class<?> clazz =Class.forName(className); if(clazz.isAnnotationPresent(HController.class)){ ioc.put(toLowerFirstWord(clazz.getSimpleName()),clazz.newInstance()); }else{ continue; } } catch (Exception e) { e.printStackTrace(); continue; } } } private void initHandlerMapping(){ if(ioc.isEmpty()){ return; } try { for (Entry<String, Object> entry: ioc.entrySet()) { Class<? extends Object> clazz = entry.getValue().getClass(); if(!clazz.isAnnotationPresent(HController.class)){ continue; } //拼url时,是controller头的url拼上方法上的url String baseUrl =""; if(clazz.isAnnotationPresent(HRequestMapping.class)){ HRequestMapping annotation = clazz.getAnnotation(HRequestMapping.class); baseUrl=annotation.value(); } Method[] methods = clazz.getMethods(); for (Method method : methods) { if(!method.isAnnotationPresent(HRequestMapping.class)){ continue; } HRequestMapping annotation = method.getAnnotation(HRequestMapping.class); String url = annotation.value(); url =(baseUrl+"/"+url).replaceAll("/+", "/"); handlerMapping.put(url,method); controllerMap.put(url,clazz.newInstance()); System.out.println(url+","+method); } } } catch (Exception e) { e.printStackTrace(); } } /** * 把字符串的首字母小写 * @param name * @return */ private String toLowerFirstWord(String name){ char[] charArray = name.toCharArray(); charArray[0] += 32; return String.valueOf(charArray); } }

还有web.xml和一个jar包依赖：

<?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/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">  <servlet> <servlet-name>MySpringMVC</servlet-name> <servlet-class>com.liugh.servlet.MyDispatcherServlet</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>MySpringMVC</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> </web-app> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>springmvc</groupId> <artifactId>springmvc</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>springmvc</name> <url>http://maven.apache.org</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency>  <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.0.1</version> <scope>provided</scope> </dependency> </dependencies> </project>

application.properties：

scanPackage=controller

这是我的整个项目结构流程详解 ⑴ 用户发送请求至前端控制器MyDispatcherServlet（xml拦截所有请求） ⑵ DispatcherServlet收到前台发出的请求调用HandlerMapping映射器。 ⑶ 处理器映射器根据请求url找到具体的映射器，生成处理器对象及处理器拦截器(如果有则生成)一并返回给DispatcherServlet。 ⑷ DispatcherServlet通过HandlerAdapter处理器适配器调用处理器 ⑸ 执行处理器(HController，也叫后端控制器)。 ⑹ HController执行完成返回ModelAndView ⑺ HandlerAdapter将Hcontroller执行结果ModelAndView返回给MyDispatcherServlet ⑻ MyDispatcherServlet将ModelAndView传给ViewReslover视图解析器 ⑼ ViewReslover解析后返回具体View ⑽ MyDispatcherServlet对View进行渲染视图（即将数据填充至视图中）。 ⑾ MyDispatcherServlet返回响应给用户。

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