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声明：

本文实现SpringMVC基本功能，注释加在代码里面，本文最后有gitee上源码地址

Main

public class Main {//类一加载就执行这个静态块static {//当前类所在的路径String path = Main.class.getResource("").getPath();//当前类所在的包名String packageName = Main.class.getPackage().getName();HeaboyMvc.scanner(path,packageName);}public static void main(String[] args) {HeaboyMvc.exec("","");HeaboyMvc.exec("test","index1");HeaboyMvc.exec("test","");System.out.println("Hello World!");}
}

• 我们执行程序从这个类开始，类加载的时候，先执行静态块（扫描所有的文件，把类文件的实例和类文件的方法 用HashMap存起来）
• main方法中的exec是模拟调用接口，第一个参数是类的@RequestMapping的value值，第二个参数是方法的@ReqeustMapping的value值
   

HeaboyMvc

public class HeaboyMvc {//存类的方法private static HashMap<String, Map<String,Method>> map=new HashMap<>();//存类的实例private static HashMap<String, Object> objMap=new HashMap<>();public static void exec(String classPath,String methodPath){if(objMap.get(classPath)==null){System.out.println("没有这个类 404");}else {if(map.get(classPath).get(methodPath)==null){System.out.println("没有这个方法 404");}else {try {map.get(classPath).get(methodPath).invoke(objMap.get(classPath));} catch (IllegalAccessException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();}}}}public static void scanner(String path,String packageName){//扫描目录下所有的文件夹//拿到了所有文件的路径List<String> paths = traverseFolder2(path);for (String p : paths) {//拿到文件的名p=p.substring(path.length()-1);try {//用包名和一些替换加上文件名得到全限定名String className=packageName+"."+p.replaceAll( Matcher.quoteReplacement(File.separator),".");String replace = className.replace(".class", "");//拿到类的信息Class<?> cl = ClassLoader.getSystemClassLoader().loadClass(replace);//判断是否为Controllerif(isController(cl)){//判断是否加RequestMappingif(isRequestMapping(cl)){//拿到注解RequestMapping requestMapping = getRequestMapping(cl);//判断注解中的值是否重复if(map.containsKey(requestMapping.value())){throw  new RuntimeException("类多注解值："+requestMapping.value());}else {//没有重复就把类放两个map进去map.put(requestMapping.value(),new HashMap<>());objMap.put(requestMapping.value(),cl.newInstance());}//拿到类中的方法Method[] declaredMethods = cl.getDeclaredMethods();//遍历类中的方法for (Method declaredMethod : declaredMethods) {if(isRequestMapping(declaredMethod)){RequestMapping mapping = getRequestMapping(declaredMethod);if(map.get(requestMapping.value()).containsKey(mapping.value())){throw  new RuntimeException("方法多注解值："+requestMapping.value());}else {//把当前的类方法存起来map.get(requestMapping.value()).put(mapping.value(),declaredMethod);}}}}else {throw  new RuntimeException("类无requestMapping");}}} catch (ClassNotFoundException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (InstantiationException e) {e.printStackTrace();}}}private static boolean isController(Class cl){Annotation annotation = cl.getAnnotation(Controller.class);if(annotation!=null){return  true;}return false;}private static boolean isRequestMapping(Class cl){Annotation annotation = cl.getAnnotation(RequestMapping.class);if(annotation!=null){return  true;}return false;}private  static boolean isRequestMapping(Method method){Annotation annotation = method.getAnnotation(RequestMapping.class);if(annotation!=null){return  true;}return false;}private static RequestMapping getRequestMapping(Class cl){Annotation annotation = cl.getAnnotation(RequestMapping.class);if(annotation instanceof  RequestMapping){return  (RequestMapping) annotation;}return null;}private static RequestMapping getRequestMapping(Method method){Annotation annotation = method.getAnnotation(RequestMapping.class);if(annotation instanceof  RequestMapping){return  (RequestMapping) annotation;}return null;}private static List<String> traverseFolder2(String path) {//路径转化为文件File file = new File(path);List<String> classFiles=new ArrayList<>();if (file.exists()) {//新建list用来存放文件LinkedList<File> list = new LinkedList<File>();File[] files = file.listFiles();//遍历for (File file2 : files) {//只要是文件夹就添加进listif (file2.isDirectory()) {list.add(file2);} else {//不是文件夹就放到classFiles中classFiles.add(file2.getAbsolutePath());}}File temp_file;//如果文件夹不空，就一直循环找文件while (!list.isEmpty()) {temp_file = list.removeFirst();files = temp_file.listFiles();for (File file2 : files) {if (file2.isDirectory()) {list.add(file2);} else {classFiles.add(file2.getAbsolutePath());}}}} else {}//获得所有文件的路径return classFiles;}
}

• 先扫包，如果是文件夹就放到list中，如果不是文件夹就是文件就放到classFiles中，判断list是否为空，如果不为空就把存进的文件夹的文件展示出来继续遍历，同时把此文件夹从list中取出，经过几次之后，就可以获得所有得到类文件的路径  
• 遍历classFiles，拿到包名，对遍历出的类文件的路径进行替换和截取，获得了类的全限定名，判断加没加@Controller注解，再判断加没加@RequestMapping注解，判断@RequeatMapping注解中的value是否重复，如果不重复就把此value存起来，并对此类中的方法进行遍历，如果方法加了@RequestMapping，就用map把方法的value也存起来

注解 

Controller

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @ interface Controller {
}

RequestMapping 

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE,ElementType.METHOD})
public @interface RequestMapping {/**** @return*/String value() default "";
}

TestController

@Controller
@RequestMapping("test")
public class TestController {@RequestMappingpublic  String index(){System.out.println("test->index");return "";}@RequestMapping("index1")public  String index1(){System.out.println("test->index1");return "";}
}