public interface HandlerMapping {
     ...  
	@Nullable
	HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
}

public interface HandlerAdapter {
	boolean supports(Object handler);
	
	@Nullable
	ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
	
	@Deprecated
	long getLastModified(HttpServletRequest request, Object handler);
}

                ....
				mappedHandler = getHandler(processedRequest);
				if (mappedHandler == null) {
					noHandlerFound(processedRequest, response);
					return;
				}
                ....
				//寻找上面返回的handler对应的HandlerAdapter 
				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

	protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
		if (this.handlerAdapters != null) {
			for (HandlerAdapter adapter : this.handlerAdapters) {
				if (adapter.supports(handler)) {
					return adapter;
				}
			}
		}
		throw new ServletException("No adapter for handler [" + handler +
				"]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
	}

				// Determine handler adapter for the current request.
				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

				// Process last-modified header, if supported by the handler.
				String method = request.getMethod();
				boolean isGet = HttpMethod.GET.matches(method);
				if (isGet || HttpMethod.HEAD.matches(method)) {
					long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
					if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
						return;
					}
				}

				if (!mappedHandler.applyPreHandle(processedRequest, response)) {
					return;
				}

				//通过HandlerAdapter的handle方法返回一个ModelAndView
				mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

@Handler
public class AnyType{}

public class SimpleControllerHandlerAdapter implements HandlerAdapter {

	@Override
	public boolean supports(Object handler) {
		return (handler instanceof Controller);
	}

	@Override
	@Nullable
	public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {

		return ((Controller) handler).handleRequest(request, response);
	}

	@Override
	@SuppressWarnings("deprecation")
	public long getLastModified(HttpServletRequest request, Object handler) {
		if (handler instanceof LastModified) {
			return ((LastModified) handler).getLastModified(request);
		}
		return -1L;
	}

}

	private void initHandlerAdapters(ApplicationContext context) {
		this.handlerAdapters = null;
        //默认会去搜索容器内所有类型为HandlerAdapter的Bean 
		if (this.detectAllHandlerAdapters) {
			Map<String, HandlerAdapter> matchingBeans =
					BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerAdapter.class, true, false);
			//如果用户往容器中放入了相关HandlerAdapter实现Bean		
			if (!matchingBeans.isEmpty()) {
				this.handlerAdapters = new ArrayList<>(matchingBeans.values());
				//排序---order接口
				AnnotationAwareOrderComparator.sort(this.handlerAdapters);
			}
		}
		else {
			try {
			   //如果我们将detectAllHandlerAdapters设置为false,那么默认只会去容器中
			   //寻找beanName为handlerAdapter的Bean
				HandlerAdapter ha = context.getBean(HANDLER_ADAPTER_BEAN_NAME, HandlerAdapter.class);
				this.handlerAdapters = Collections.singletonList(ha);
			}
			catch (NoSuchBeanDefinitionException ex) {
				// Ignore, we'll add a default HandlerAdapter later.
			}
		}

		//如果没找到,那么采用默认的策略
		if (this.handlerAdapters == null) {
			this.handlerAdapters = getDefaultStrategies(context, HandlerAdapter.class);
			if (logger.isTraceEnabled()) {
				logger.trace("No HandlerAdapters declared for servlet '" + getServletName() +
						"': using default strategies from DispatcherServlet.properties");
			}
		}
	}

	protected <T> List<T> getDefaultStrategies(ApplicationContext context, Class<T> strategyInterface) {
	//第一次进来时,首先初始化
		if (defaultStrategies == null) {
			try {
			//加载DispatcherServlet类路径下的DispatcherServlet.properties文件
				ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class);
				//加载该文件
				defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
			}
			catch (IOException ex) {
				throw new IllegalStateException("Could not load '" + DEFAULT_STRATEGIES_PATH + "': " + ex.getMessage());
			}
		}
        //key就是要寻找的默认类路径---这里对应上面为handlerAdapter的全类名
		String key = strategyInterface.getName();
		//去配置文件中定位默认组件---如果存在多个,使用逗号分割
		String value = defaultStrategies.getProperty(key);
		if (value != null) {
		//如果默认配置存在的话，按照逗号分割,拿到所有默认实现类的每一个全类名
			String[] classNames = StringUtils.commaDelimitedListToStringArray(value);
			List<T> strategies = new ArrayList<>(classNames.length);
			for (String className : classNames) {
				try {
					Class<?> clazz = ClassUtils.forName(className, DispatcherServlet.class.getClassLoader());
					//实例化后,放入容器中
					Object strategy = createDefaultStrategy(context, clazz);
					strategies.add((T) strategy);
				}
				catch (ClassNotFoundException ex) {
					throw new BeanInitializationException(
							"Could not find DispatcherServlet's default strategy class [" + className +
							"] for interface [" + key + "]", ex);
				}
				catch (LinkageError err) {
					throw new BeanInitializationException(
							"Unresolvable class definition for DispatcherServlet's default strategy class [" +
							className + "] for interface [" + key + "]", err);
				}
			}
			return strategies;
		}
		else {
			return Collections.emptyList();
		}
	}

public class AnnoHandlerMapping extends AbstractHandlerMapping implements InitializingBean {
   //封装扫描到的所有标注了@Controller注解的handler
    private static List<ControllerHolder> controllerHolders;


    @Override
    public void afterPropertiesSet() throws Exception {
        ApplicationContext app = getApplicationContext();
        if (app != null) {
            //扫描+解析
            Set<Map.Entry<String, Object>> handlers = app.getBeansWithAnnotation(Controller.class).entrySet();
            controllerHolders=new ArrayList<>();
            for (Map.Entry<String, Object> handler : handlers) {
                controllerHolders.add(ControllerHolder.parserController(handler.getValue()));
            }
        }
    }

   
    @Override
    protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
        String reqURI = request.getRequestURI();
        for (ControllerHolder controllerHolder : controllerHolders) {
            Method method = controllerHolder.getMappings().get(reqURI);
            if(method==null){
                continue;
            }
            //设置当前正在执行的方法和方法实参列表值
            controllerHolder.setCurMethod(method);
            controllerHolder.setParamsVal(request);
            //返回ControllerHolder 
            return controllerHolder;
        }
        return null;
    }


    @Data
    public static class ControllerHolder{
       //封装目标对象
        private Object controller;
      //处理当前请求的方法
        private Method curMethod;
     //方法实参    
        private Object[] paramsVal;
    //当前目标handler对象中请求路径和方法的映射关系 
        private Map<String,Method> mappings;
    //方法和当前方法中参数信息封装     
        private Map<Method,List<MethodParam>> methodParams;
     //用于类型转换
         private TypeConverter typeConverter=new SimpleTypeConverter();

        public ControllerHolder(Object controller, Map<String, Method> mappings, Map<Method,List<MethodParam>> methodParams) {
            this.controller = controller;
            this.mappings = mappings;
            this.methodParams=methodParams;
        }
       
       //解析controller对象   
        public static ControllerHolder parserController(Object controller){
            Method[] methods = controller.getClass().getMethods();
            Map<String,Method> mappings=new HashMap<>();
            Map<Method,List<MethodParam>> methodParams=new HashMap<>();
            //解析controller对象中所有方法
            for (Method method : methods) {
                //获取方法上标注的@RequestMapping注解
                RequestMapping req = method.getAnnotation(RequestMapping.class);
                //没有标注该注解的方法不会被作为处理请求的方法
                if(req==null){
                    continue;
                }
                //当前方法和对应请求的映射
                mappings.put(req.value()[0],method);
                //当前方法和对应方法参数信息的封装
                methodParams.put(method,parseMethodParam(method));
            }
            return new ControllerHolder(controller,mappings,methodParams);
        }

        private static List<MethodParam> parseMethodParam(Method method) {
            List<MethodParam> paramNames=new ArrayList<>();
             //方法参数挨个解析--MethodParam封装方法参数名和对应的方法参数类型
            for (Parameter parameter : method.getParameters()) {
                RequestParam annotation = parameter.getAnnotation(RequestParam.class);
                Assert.notNull(annotation,"方法参数上必须要标注@RequestParam注解");
                paramNames.add(new MethodParam(annotation.value(), parameter.getType()));
            }
            return paramNames;
        }

        public void setParamsVal(HttpServletRequest request) {
            this.paramsVal=getParamValue(methodParams.get(curMethod),request);
        }

        private Object[] getParamValue(List<MethodParam> methodParams, HttpServletRequest request) {
         //从request的请求参数集合中取出当参数值,然后根据参数类型判断是否需要进行类型转换
            Object[] paramVals = new Object[methodParams.size()];
            for (int i = 0; i < methodParams.size(); i++) {
                MethodParam methodParam = methodParams.get(i);                     paramVals[i]=typeConverter.convertIfNecessary(request.getParameter(methodParams.get(i).paramName),methodParam.paramClass);
            }
            return paramVals;
        }
    }

    @Data
    @AllArgsConstructor
    public static class MethodParam{
        private String paramName;
        private Class<?> paramClass;
    }
}

public class AnnoHandlerAdaptor implements HandlerAdapter {
    @Override
    public boolean supports(Object handler) {
        return handler.getClass().isAssignableFrom(AnnoHandlerMapping.ControllerHolder.class);
    }

    @Override
    public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        AnnoHandlerMapping.ControllerHolder controllerHolder = (AnnoHandlerMapping.ControllerHolder) handler;
        //触发方法的调用,将返回值进行封装
        Object res = controllerHolder.getCurMethod().invoke(controllerHolder.getController(), controllerHolder.getParamsVal());
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.addObject(res);
        //例如我们自定义的JsonView将返回结果输出为JSON后返回
        modelAndView.setView(new JsonView());
        return modelAndView;
    }

    @Override
    public long getLastModified(HttpServletRequest request, Object handler) {
        return -1;
    }
}

@Slf4j
public class JsonView extends AbstractView {
    private ObjectMapper objectMapper = new ObjectMapper();
    private JsonEncoding encoding=JsonEncoding.UTF8;

    public JsonView() {
        setContentType("application/json");
    }

    @Override
    protected void renderMergedOutputModel(Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
            writeContent(outputStream,model,null);
            writeToResponse(response,outputStream);
    }


    protected void writeContent(OutputStream stream, Object value, String jsonPrefix) throws IOException {
        JsonGenerator generator = this.objectMapper.getJsonFactory().createJsonGenerator(stream, this.encoding);

        if (this.objectMapper.isEnabled(SerializationFeature.INDENT_OUTPUT)) {
            generator.useDefaultPrettyPrinter();
        }

        if (jsonPrefix != null) {
            generator.writeRaw(jsonPrefix);
        }

        this.objectMapper.writeValue(generator, value);
    }
}

     <bean id="handlerMapping" class="com.example.AnnoHandlerMapping"/>
     <bean id="handlerAdaptor" class="com.example.AnnoHandlerAdaptor"/>
     <bean id="helloController" class="com.example.HelloController"/>

@Controller
public class HelloController {
    @RequestMapping("/hello")
    public Stu sayHello(@RequestParam("name") String name, @RequestParam("age") Integer age){
        return new Stu(name,age);
    }
}