package com.lonely.wolf.note.springboot.demo;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/hello")
public class HelloController {
    @GetMapping("/demo")
    public String helloWorld(String name){
        return "Hello：" + name;
    }
}

package com.lonely.wolf.note.springboot;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication(scanBasePackages = "com.lonely.wolf.note.springboot")
class MySpringBootApplication {
    public static void main(String[] args) {
        SpringApplication.run(MySpringBootApplication.class, args);
    }
}

package com.lonely.wolf.mini.spring.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * 原始Servlet接口编写，一般需要实现GET和POST方法，其他方法可以视具体情况选择性继承
 */
public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().write("Hello：" + request.getParameter("name"));
    }
}

package com.lonely.wolf.mini.spring.annotation;

import java.lang.annotation.*;

@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface WolfAutowired {
    String value() default "";
}

package com.lonely.wolf.mini.spring.annotation;

import java.lang.annotation.*;

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

package com.lonely.wolf.mini.spring.annotation;

import java.lang.annotation.*;

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

package com.lonely.wolf.mini.spring.annotation;

import java.lang.annotation.*;

@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface WolfRequestParam {
    String value() default "";
}

package com.lonely.wolf.mini.spring.annotation;

import java.lang.annotation.*;

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

package com.lonely.wolf.mini.spring.v1;

import com.lonely.wolf.mini.spring.annotation.*;
import com.lonely.wolf.mini.spring.v1.config.MyConfig;
import org.apache.commons.lang3.StringUtils;

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.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.*;

public class MyDispatcherServlet extends HttpServlet {
    private MyConfig myConfig = new MyConfig();
    private List<String> classNameList = new ArrayList<String>();

    private Map<String,Object> iocContainerMap = new HashMap<>();
    private Map<String,HandlerMapping> handlerMappingMap = new HashMap<>();

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            this.doDispatch(request, response);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception{
        String requestUrl = this.formatUrl(request.getRequestURI());
        HandlerMapping handlerMapping = handlerMappingMap.get(requestUrl);
        if (null == handlerMapping){
            response.getWriter().write("404 Not Found");
            return;
        }

        //获取方法中的参数类型
        Class<?>[] paramTypeArr = handlerMapping.getMethod().getParameterTypes();
        Object[] paramArr = new Object[paramTypeArr.length];

        for (int i=0;i<paramTypeArr.length;i++){
            Class<?> clazz = paramTypeArr[i];
            //参数只考虑三种类型，其他不考虑
            if (clazz == HttpServletRequest.class){
                paramArr[i] = request;
            }else if (clazz == HttpServletResponse.class){
                paramArr[i] = response;
            } else if (clazz == String.class){
                Map<Integer,String> methodParam = handlerMapping.getMethodParams();
                paramArr[i] = request.getParameter(methodParam.get(i));
            }else{
                System.out.println("暂不支持的参数类型");
            }
        }
        //反射调用controller方法
        handlerMapping.getMethod().invoke(handlerMapping.getTarget(), paramArr);
    }

    private String formatUrl(String requestUrl) {
        requestUrl = requestUrl.replaceAll("/+","/");
        if (requestUrl.lastIndexOf("/") == requestUrl.length() -1){
            requestUrl = requestUrl.substring(0,requestUrl.length() -1);
        }
        return requestUrl;
    }


    @Override
    public void init(ServletConfig config) throws ServletException {
        //1.加载配置文件
        try {
            doLoadConfig(config.getInitParameter("defaultConfig"));
        } catch (Exception e) {
            System.out.println("加载配置文件失败");
            return;
        }

        //2.根据获取到的扫描路径进行扫描
        doScanPacakge(myConfig.getBasePackages());

        //3.将扫描到的类进行初始化，并存放到IOC容器
        doInitializedClass();

        //4.依赖注入
        doDependencyInjection();

        System.out.println("DispatchServlet Init End..." );
    }


    private void doDependencyInjection() {
        if (iocContainerMap.size() == 0){
            return;
        }
        //循环IOC容器中的类
        Iterator<Map.Entry<String,Object>> iterator = iocContainerMap.entrySet().iterator();

        while (iterator.hasNext()){
            Map.Entry<String,Object> entry = iterator.next();
            Class<?> clazz = entry.getValue().getClass();
            Field[] fields = clazz.getDeclaredFields();

            //属性注入
            for (Field field : fields){
                //如果属性有WolfAutowired注解则注入值（暂时不考虑其他注解）
                if (field.isAnnotationPresent(WolfAutowired.class)){
                    String value = toLowerFirstLetterCase(field.getType().getSimpleName());//默认bean的value为类名首字母小写
                    if (field.getType().isAnnotationPresent(WolfService.class)){
                        WolfService wolfService = field.getType().getAnnotation(WolfService.class);
                        value = wolfService.value();
                    }
                    field.setAccessible(true);
                    try {
                        Object target = iocContainerMap.get(beanName);
                        if (null == target){
                            System.out.println(clazz.getName() + "required bean:" + beanName + ",but we not found it");
                        }
                        field.set(entry.getValue(),iocContainerMap.get(beanName));//初始化对象，后面注入
                    } catch (IllegalAccessException e) {
                        e.printStackTrace();
                    }
                }
            }

            //初始化HanderMapping
            String requestUrl = "";
            //获取Controller类上的请求路径
            if (clazz.isAnnotationPresent(WolfController.class)){
                requestUrl = clazz.getAnnotation(WolfController.class).value();
            }

            //循环类中的方法，获取方法上的路径
            Method[] methods = clazz.getMethods();
            for (Method method : methods){
                //假设只有WolfGetMapping这一种注解
                if(!method.isAnnotationPresent(WolfGetMapping.class)){
                    continue;
                }
                WolfGetMapping wolfGetMapping = method.getDeclaredAnnotation(WolfGetMapping.class);
                requestUrl = requestUrl + "/" + wolfGetMapping.value();//拼成完成的请求路径

                //不考虑正则匹配路径/xx/* 的情况，只考虑完全匹配的情况
                if (handlerMappingMap.containsKey(requestUrl)){
                    System.out.println("重复路径");
                    continue;
                }

                Annotation[][] annotationArr = method.getParameterAnnotations();//获取方法中参数的注解

                Map<Integer,String> methodParam = new HashMap<>();//存储参数的顺序和参数名
                retryParam:
                for (int i=0;i<annotationArr.length;i++){
                    for (Annotation annotation : annotationArr[i]){
                        if (annotation instanceof WolfRequestParam){
                            WolfRequestParam wolfRequestParam = (WolfRequestParam) annotation;
                            methodParam.put(i,wolfRequestParam.value());//存储参数的位置和注解中定义的参数名
                            continue retryParam;
                        }
                    }
                }

                requestUrl = this.formatUrl(requestUrl);//主要是防止路径多了/导致路径匹配不上
                HandlerMapping handlerMapping = new HandlerMapping();
                handlerMapping.setRequestUrl(requestUrl);//请求路径
                handlerMapping.setMethod(method);//请求方法
                handlerMapping.setTarget(entry.getValue());//请求方法所在controller对象
                handlerMapping.setMethodParams(methodParam);//请求方法的参数信息
                handlerMappingMap.put(requestUrl,handlerMapping);//存入hashmap
            }
        }
    }


    /**
     * 初始化类，并放入容器iocContainerMap内
     */
    private void doInitializedClass() {
        if (classNameList.isEmpty()){
            return;
        }
        for (String className : classNameList){
            if (StringUtils.isEmpty(className)){
                continue;
            }
            Class clazz;
            try {
                clazz = Class.forName(className);//反射获取对象
                if (clazz.isAnnotationPresent(WolfController.class)){
                    String value = ((WolfController)clazz.getAnnotation(WolfController.class)).value();
                    //如果直接指定了value则取value，否则取首字母小写类名作为key值存储类的实例对象
                    iocContainerMap.put(StringUtils.isBlank(value) ? toLowerFirstLetterCase(clazz.getSimpleName()) : value,clazz.newInstance());
                }else if(clazz.isAnnotationPresent(WolfService.class)){
                    String value = ((WolfService)clazz.getAnnotation(WolfService.class)).value();
                    iocContainerMap.put(StringUtils.isBlank(value) ? toLowerFirstLetterCase(clazz.getSimpleName()) : value,clazz.newInstance());
                }else{
                    System.out.println("不考虑其他注解的情况");
                }
            } catch (Exception e) {
                e.printStackTrace();
                System.out.println("初始化类失败，className为" + className);
            }
        }

    }

    /**
     * 将首字母转换为小写
     * @param className
     * @return
     */
    private String toLowerFirstLetterCase(String className) {
        if (StringUtils.isBlank(className)){
            return "";
        }
        String firstLetter = className.substring(0,1);
        return firstLetter.toLowerCase() + className.substring(1);
    }


    /**
     * 扫描包下所有文件获取全限定类名
     * @param basePackages
     */
    private void doScanPacakge(String basePackages) {
        if (StringUtils.isBlank(basePackages)){
            return;
        }
        //把包名的.替换为/
        String scanPath = "/" + basePackages.replaceAll("\\.","/");
        URL url = this.getClass().getClassLoader().getResource(scanPath);//获取到当前包所在磁盘的全路径
        File files = new File(url.getFile());//获取当前路径下所有文件
        for (File file : files.listFiles()){//开始扫描路径下的所有文件
            if (file.isDirectory()){//如果是文件夹则递归
                doScanPacakge(basePackages + "." + file.getName());
            }else{//如果是文件则添加到集合。因为上面是通过类加载器获取到的文件路径，所以实际上是class文件所在路径
                classNameList.add(basePackages + "." + file.getName().replace(".class",""));
            }
        }

    }


    /**
     * 加载配置文件
     * @param configPath - 配置文件所在路径
     */
    private void doLoadConfig(String configPath) {
        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream(configPath);
        Properties properties = new Properties();
        try {
            properties.load(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("加载配置文件失败");
        }

        properties.forEach((k, v) -> {
            try {
                Field field = myConfig.getClass().getDeclaredField((String)k);
                field.setAccessible(true);
                field.set(myConfig,v);
            } catch (Exception e) {
                e.printStackTrace();
                System.out.println("初始化配置类失败");
                return;
            }
        });
    }
}

package com.lonely.wolf.mini.spring.v1;

import java.lang.reflect.Method;
import java.util.Map;

//省略了getter/setter方法
public class HandlerMapping {
    private String requestUrl;
    private Object target;//保存方法对应的实例
    private Method method;//保存映射的方法
    private Map<Integer,String> methodParams;//记录方法参数
}

package com.lonely.wolf.mini.spring.controller;

import com.lonely.wolf.mini.spring.annotation.WolfAutowired;
import com.lonely.wolf.mini.spring.annotation.WolfController;
import com.lonely.wolf.mini.spring.annotation.WolfGetMapping;
import com.lonely.wolf.mini.spring.annotation.WolfRequestParam;
import com.lonely.wolf.mini.spring.service.HelloService;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WolfController
public class HelloController {
    @WolfAutowired
    private HelloService helloService;

    @WolfGetMapping("/hello")
    public void query(HttpServletRequest request,HttpServletResponse response, @WolfRequestParam("name") String name) throws IOException {
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().write("Hello：" + name);
    }
}

package com.lonely.wolf.mini.spring.service;

import com.lonely.wolf.mini.spring.annotation.WolfService;

@WolfService(value = "hello_service")//为了演示能否正常取value属性
public class HelloService {
}