SpringMVC简单仿写

我会带着你远行 2024-03-26 20:08 40阅读 0赞

> 之前我分享过SpringMVC的基本原理与配置（原文链接：[https://blog.csdn.net/L170311/article/details/129339120][https_blog.csdn.net_L170311_article_details_129339120]）,为了更深层次的学习，精益求精，手动仿写了一个MVC原理实现demo，一起学习一下吧

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### 结构目录： ###

![c96180d05b6e4bebb817407cf5eb505b.png][]

两个自定义注解，两个Controller,核心ImitateSpringMVC，以及测试Main

#### @Controller和@RequestMapping ####

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

@Documented

该注解的作用就是在生产文档的时候，保留自定义注解的存在，例如：

\-d doc Test.java ； 如果Test.java中有自定义的注解，然后该注解上面有@Documented，那么生成的文档中就会包含自定义注解部分，反之就没有。

@Retention(RetentionPolicy.RUNTIME)

![fa6a7251a6de4b348386b4d0b23a7566.png][]  
@Target(ElementType.TYPE)

> target英文有目标、目的的意思。 @Target在java中是注释类。@Target作用于修饰的注释可以修饰的类型范围
> 
> @Target包含一个ElementType\[\]元素类型的数组。ElementType\[\]数组值value，表明Target修饰的注释可以修饰的类型范围。ElementType枚举值包含方法、属性、类等等。
> 
> ANNOTATION\_TYPE: 注解只能修饰注解，不能修饰其他的东西
> 
> CONSTRUCTOR: 注解只能修饰构造方法
> 
> FIELD: 注解只能修饰属性(成员变量) 字段加解密注解标记拦截
> 
> LOCAL\_VARIABLE: 注解只能修饰局部变量
> 
> METHOD: 注解只能修饰方法 对应的方法进行拦截
> 
> PACKAGE: 注解只能修饰包
> 
> PARAMETER: 注解只能修饰方法的参数
> 
> TYPE: 注解只能修饰类、接口、枚举

#### TestController ####

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

#### 核心：ImitateSpringMVC ####

public class ImitateSpringMVC {
        private static HashMap<String, Map<String, Method>> map=new HashMap<>();
        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){
            //遍历当前路径下的所有文件
            List<String> paths = traverseFolder2(path);
            for (String p : paths) {
                p=p.substring(path.length()-1);
                try {
                    String className=packageName+"."+p.replaceAll( Matcher.quoteReplacement(File.separator),".");
                    String replace = className.replace(".class", "");
    
                    //通过类加载器加载类信息
                    Class<?> cl = ClassLoader.getSystemClassLoader().loadClass(replace);
                    if(isController(cl)){
                        if(isRequestMapping(cl)){
    
                            //获得我们设置在@RequestMapping里的值
                            RequestMapping requestMapping = getRequestMapping(cl);
    
                            //如果注解值重复，抛异常
                            if(map.containsKey(requestMapping.value())){
                                throw  new RuntimeException("类多注解值："+requestMapping.value());
                            }else {
                                map.put(requestMapping.value(),new HashMap<>());
                                objMap.put(requestMapping.value(),cl.newInstance());
                            }
    
                            //获得当前类对象声明的所有方法
                            Method[] declaredMethods = cl.getDeclaredMethods();
                            for (Method declaredMethod : declaredMethods) {
    
                                //遍历，判定方法是否带有@RequestMapping注解
                                if(isRequestMapping(declaredMethod)){
                                    RequestMapping mapping = getRequestMapping(declaredMethod);
    
                                    //判定方法的注解值是否重复
                                    if(map.get(requestMapping.value()).containsKey(mapping.value())){
                                        throw  new RuntimeException("方法多注解值："+requestMapping.value());
                                    }else {
                                        map.get(requestMapping.value()).put(mapping.value(),declaredMethod);
                                        //现在的map<K,V>中k是我们获取到类对象的@RequestMapping的值，V是类对象方法的@RequestMapping的值，组成的一个集合
                                    }
                                }
                            }
                        }else {
                            throw  new RuntimeException("类无requestMapping");
                        }
                    }
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                } catch (InstantiationException e) {
                    e.printStackTrace();
                }
            }
    
    
        }
    
        //判定类文件是否带有@Controller注解
        private static boolean isController(Class cl){
            Annotation annotation = cl.getAnnotation(Controller.class);
            if(annotation!=null){
                return  true;
            }
            return false;
        }
        //判定类文件是否带有@RequestMapping注解
        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) {
            File file = new File(path);
            List<String> classFiles=new ArrayList<>();
            //如果文件存在，开始遍历
            if (file.exists()) {
                LinkedList<File> list = new LinkedList<File>();
                File[] files = file.listFiles();
                for (File file2 : files) {
                    //如果文件是文件夹的形式，放入list
                    if (file2.isDirectory()) {
                        list.add(file2);
                    } else {
                        classFiles.add(file2.getAbsolutePath());
                    }
                }
                File temp_file;
                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 {
    
            }
    
            return classFiles;
        }
    }

![896f5da7f74246b994e32a67a6f6a0c7.png][]

![736c04ca9a5d404c941ff97499fb4ed8.png][]

#### IndexController ####

@Controller
    @RequestMapping
    public class IndexController {
        @RequestMapping
        public  void index(){
            System.out.println("index -> index");
        }
    
    }

#### Main ####

public class Main {
        static {
            //获得当前类的路径
            String path = Main.class.getResource("").getPath();
            //获得当前类的包名
            String packageName = Main.class.getPackage().getName();
            //传入到MVC的方法中
            ImitateSpringMVC.scanner(path,packageName);
        }
    
        public static void main(String[] args) {
            ImitateSpringMVC.exec("","");
            ImitateSpringMVC.exec("test","index1");
            ImitateSpringMVC.exec("test","");
            System.out.println("SpringMVC！");
        }
    
    
    }

--------------------

demo已上传gitee平台：[https://gitee.com/dont-live-in-the-past/spring-mvc-simple-imitation][https_gitee.com_dont-live-in-the-past_spring-mvc-simple-imitation]

![35d269ace3f04419a62cb18d13e787a3.jpeg][]

[https_blog.csdn.net_L170311_article_details_129339120]: https://blog.csdn.net/L170311/article/details/129339120
[c96180d05b6e4bebb817407cf5eb505b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/344c760b637746d59dd19679191338ab.png
[fa6a7251a6de4b348386b4d0b23a7566.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/073666e7f9744e11a992f5fea7b121f4.png
[896f5da7f74246b994e32a67a6f6a0c7.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/4161ee781b784e53965d4927498005d4.png
[736c04ca9a5d404c941ff97499fb4ed8.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/1217f844927245c3b98462a941f4c1bc.png
[https_gitee.com_dont-live-in-the-past_spring-mvc-simple-imitation]: https://gitee.com/dont-live-in-the-past/spring-mvc-simple-imitation
[35d269ace3f04419a62cb18d13e787a3.jpeg]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/9ce2d7c04722484c87e63046592e4c76.png