手写高仿真Spring框架-MVC

手写高仿真Spring框架

流行词：顶层设计 MVC

参考代码：https://gitee.com/li-lixiang/lean-spring-2.0.git

 

MVC实现

1. 初始化ApplicationContext
2. 初始化Spring MVC九大组件

    private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception{
        //1、通过从request中拿到URL，去匹配一个HandlerMapping
        GPHandlerMapping handler = getHandler(req);
        if(handler == null){
            processDispatchResult(req,resp,new GPModelAndView("404"));
            return;
        }

        //2、准备调用前的参数
        GPHandlerAdapter ha = getHandlerAdapter(handler);

        //3、真正的调用方法,返回ModelAndView存储了要穿页面上值，和页面模板的名称
        GPModelAndView mv = ha.handle(req,resp,handler);

        //这一步才是真正的输出
        processDispatchResult(req, resp, mv);
    }

初始化ApplicationContext在前面blog中已经说明实现原理和主要逻辑

context = new GPApplicationContext(config.getInitParameter(CONTEXT_CONFIG_LOCATION));

Spring MVC 中必须实现的方法

initHandlerMappings：将url与对应的方法封装成HandlerMapping对象，缓存起来。

    private void initHandlerMappings(GPApplicationContext context) {
        String [] beanNames = context.getBeanDefinitionNames();
        try {
            for (String beanName : beanNames) {
                Object controller = context.getBean(beanName);
                Class clazz = controller.getClass();
                if(!clazz.isAnnotationPresent(GPController.class)){
                    continue;
                }
                String baseUrl = "";
                //获取Controller的url配置
                if(clazz.isAnnotationPresent(GPRequestMapping.class)){
                    GPRequestMapping requestMapping = clazz.getAnnotation(GPRequestMapping.class);
                    baseUrl = requestMapping.value();
                }
                //获取Method的url配置
                Method[] methods = clazz.getMethods();
                for (Method method : methods) {
                    //没有加RequestMapping注解的直接忽略
                    if(!method.isAnnotationPresent(GPRequestMapping.class)){ continue; }
                    //映射URL
                    GPRequestMapping requestMapping = method.getAnnotation(GPRequestMapping.class);
                    String regex = ("/" + baseUrl + "/" + requestMapping.value().replaceAll("\\*",".*")).replaceAll("/+", "/");
                    Pattern pattern = Pattern.compile(regex);
                    this.handlerMappings.add(new GPHandlerMapping(pattern,controller,method));
                    log.info("Mapped " + regex + "," + method);
                }
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }

initHandlerAdapters：初始化适配器，适配器模式，HandlerAdapter将一个请求的所有数据变成访问某个方法

    private void initHandlerAdapters(GPApplicationContext context) {

        //把一个requet请求变成一个handler，参数都是字符串的，自动配到handler中的形参

        //可想而知，他要拿到HandlerMapping才能干活
        //就意味着，有几个HandlerMapping就有几个HandlerAdapter
        for (GPHandlerMapping handlerMapping : this.handlerMappings) {
            this.handlerAdapters.put(handlerMapping,new GPHandlerAdapter());
        }


    }

实现HandlerAdapter接口

主要实现方法：

boolean supports(Object handler);

以及方法：

ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;

supports方法获取该适配器是否支持。

handle方法进行主要逻辑处理，将request转换成某个方法进行调用后，返回ModelAndView。

    GPModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception{
        GPHandlerMapping handlerMapping = (GPHandlerMapping)handler;

        //把方法的形参列表和request的参数列表所在顺序进行一一对应
        Map paramIndexMapping = new HashMap();


        //提取方法中加了注解的参数
        //把方法上的注解拿到，得到的是一个二维数组
        //因为一个参数可以有多个注解，而一个方法又有多个参数
        Annotation[] [] pa = handlerMapping.getMethod().getParameterAnnotations();
        for (int i = 0; i < pa.length ; i ++) {
            for(Annotation a : pa[i]){
                if(a instanceof GPRequestParam){
                    String paramName = ((GPRequestParam) a).value();
                    if(!"".equals(paramName.trim())){
                        paramIndexMapping.put(paramName, i);
                    }
                }
            }
        }

        //提取方法中的request和response参数
        Class [] paramsTypes = handlerMapping.getMethod().getParameterTypes();
        for (int i = 0; i < paramsTypes.length ; i ++) {
            Class type = paramsTypes[i];
            if(type == HttpServletRequest.class ||
                    type == HttpServletResponse.class){
                paramIndexMapping.put(type.getName(),i);
            }
        }

        //获得方法的形参列表
        Map params = request.getParameterMap();

        //实参列表
        Object [] paramValues = new Object[paramsTypes.length];

        for (Map.Entry parm : params.entrySet()) {
            String value = Arrays.toString(parm.getValue()).replaceAll("\\[|\\]","")
                    .replaceAll("\\s",",");

            if(!paramIndexMapping.containsKey(parm.getKey())){continue;}

            int index = paramIndexMapping.get(parm.getKey());
            paramValues[index] = caseStringValue(value,paramsTypes[index]);
        }

        if(paramIndexMapping.containsKey(HttpServletRequest.class.getName())) {
            int reqIndex = paramIndexMapping.get(HttpServletRequest.class.getName());
            paramValues[reqIndex] = request;
        }

        if(paramIndexMapping.containsKey(HttpServletResponse.class.getName())) {
            int respIndex = paramIndexMapping.get(HttpServletResponse.class.getName());
            paramValues[respIndex] = response;
        }

        Object result = handlerMapping.getMethod().invoke(handlerMapping.getController(),paramValues);
        if(result == null || result instanceof Void){ return null; }

        boolean isModelAndView = handlerMapping.getMethod().getReturnType() == GPModelAndView.class;
        if(isModelAndView){
            return (GPModelAndView) result;
        }
        return null;
    }

回到doDispatch方法中调用processDispatchResult方法

该方法将ModelAndView处理成最后response。主要通过View.render方法渲染成前端能识别的字符串。

    private void processDispatchResult(HttpServletRequest req, HttpServletResponse resp, GPModelAndView mv) throws Exception{
        //把给我的ModleAndView变成一个HTML、OuputStream、json、freemark、veolcity
        //ContextType
        if(null == mv){return;}

        //如果ModelAndView不为null，怎么办？
        if(this.viewResolvers.isEmpty()){return;}

        for (GPViewResolver viewResolver : this.viewResolvers) {
            GPView view = viewResolver.resolveViewName(mv.getViewName(),null);
            view.render(mv.getModel(),req,resp);
            return;
        }
    }

至此，MVC整个已实现。

下面进行调试：

1、启动时，报错80端口被绑定。修改pom文件中启动的端口为81，启动成功。

2、发现返回中文直接乱码

3、发现action直接out到响应中，做一下处理，将out里面返回html格式