nosum-spring/src/main/java/cn/nosum/framework/mvc/v4/servlet/DispatcherServlet.java

package cn.nosum.framework.mvc.v4.servlet;

import cn.nosum.framework.annotation.Controller;
import cn.nosum.framework.annotation.RequestMapping;
import cn.nosum.framework.context.ApplicationContext;
import cn.nosum.util.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.lang.reflect.Method;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class DispatcherServlet extends HttpServlet {

    private ApplicationContext applicationContext;
    private List<HandlerMapping> handlerMappings = new ArrayList<HandlerMapping>();
    private Map<HandlerMapping,HandlerAdapter> handlerAdapterMap=new HashMap<HandlerMapping, HandlerAdapter>();
    private List<ViewResolver> viewResolvers=new ArrayList<ViewResolver>();


    @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 {
        //6、调用，运行阶段
        try {
            doDispatch(req, resp);
        } catch (Exception e) {
            try{
                processDispatchResult(req,resp,new ModelAndView("500"));
            }catch (Exception e1){
                e.printStackTrace();
            }
        }
    }

    private void processDispatchResult(HttpServletRequest req, HttpServletResponse resp, ModelAndView modelAndView) throws Exception {
        if(null == modelAndView){return;}
        if(this.viewResolvers.isEmpty()){return;}
        for (ViewResolver viewResolver : this.viewResolvers) {
            View view = viewResolver.resolveViewName(modelAndView.getViewName());
            // 直接往浏览器输出
            view.render(modelAndView.getModel(),req,resp);
            return;
        }
    }

    private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception {
        // 通过 request 取得 URL，匹配 handlerMapping
        HandlerMapping handlerMapping=getHandler(req);
        if(handlerMapping == null){
            processDispatchResult(req,resp,new ModelAndView("404"));
            return;
        }
        HandlerAdapter handlerAdapter = getHandlerAdapter(handlerMapping);
        ModelAndView mv = handlerAdapter.handler(req,resp,handlerMapping);
        processDispatchResult(req,resp,mv);
    }

    private HandlerAdapter getHandlerAdapter(HandlerMapping handlerMapping) {
        if(this.handlerAdapterMap.isEmpty()){return null;}
        return this.handlerAdapterMap.get(handlerMapping);
    }

    private HandlerMapping getHandler(HttpServletRequest req) {
        if(this.handlerMappings.isEmpty()){return  null;}
        String url = req.getRequestURI();
        String contextPath = req.getContextPath();
        url = url.replaceAll(contextPath,"").replaceAll("/+","/");

        for (HandlerMapping mapping : handlerMappings) {
            Matcher matcher = mapping.getPattern().matcher(url);
            if(!matcher.matches()){continue;}
            return mapping;
        }
        return null;
    }

    @Override
    public void init(ServletConfig config) throws ServletException {
        //初始化Spring核心IoC容器
        applicationContext = new ApplicationContext(config.getInitParameter("contextConfigLocation"));
        //完成了IoC、DI和MVC部分对接
        //初始化九大组件
        initStrategies(applicationContext);
        System.out.println("Spring framework is init.");
    }

    private void initStrategies(ApplicationContext context) {
        //handlerMapping
        initHandlerMappings(context);
        //初始化参数适配器
        initHandlerAdapters(context);
        //初始化视图转换器
        initViewResolvers(context);
    }

    private void initViewResolvers(ApplicationContext context) {
        String templateRoot = context.getConfig().getProperty("templateRoot");
        String templateRootPath = this.getClass().getClassLoader().getResource(templateRoot).getFile();

        File templateRootDir = new File(templateRootPath);
        for (File file : templateRootDir.listFiles()) {
            this.viewResolvers.add(new ViewResolver(templateRoot));
        }
    }

    private void initHandlerAdapters(ApplicationContext context) {
        for (HandlerMapping handlerMapping : handlerMappings) {
            this.handlerAdapterMap.put(handlerMapping,new HandlerAdapter());
        }
    }

    private void initHandlerMappings(ApplicationContext context) {
        if (context.getBeanDefinitionCount()==0){return;}
        for (String beanName : this.applicationContext.getBeanDefinitionNames()) {
            Object instance = applicationContext.getBean(beanName);
            Class<?> clazz = instance.getClass();
            if(!clazz.isAnnotationPresent(Controller.class)){ continue; }
            // 提取 class 上配置的url
            String baseUrl = "";
            if(clazz.isAnnotationPresent(RequestMapping.class)){
                RequestMapping requestMapping = clazz.getAnnotation(RequestMapping.class);
                baseUrl = requestMapping.value();
            }
            //只获取public的方法
            for (Method method : clazz.getMethods()) {
                if(!method.isAnnotationPresent(RequestMapping.class)){continue;}
                //提取每个方法上面配置的url
                RequestMapping requestMapping = method.getAnnotation(RequestMapping.class);
                String regex = ("/" + baseUrl + "/" + requestMapping.value()
                        .replaceAll("\\*",".*")) // 将 * 替换成 .*
                        .replaceAll("/+","/"); // 将多个 / 替换为一个
                Pattern pattern = Pattern.compile(regex);
                handlerMappings.add(new HandlerMapping(pattern,instance,method));
                System.out.println("Mapped : " + regex + "," + method);
            }
        }
    }
}