mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

这行代码开始就到了去反射调用业务逻辑方法，看看具体如何调用：

org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#handleInternal

org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#invokeHandlerMethod

org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod#invokeAndHandle

//核心代码非常关键

org.springframework.web.method.support.InvocableHandlerMethod#invokeForRequest

    @Nullable
    public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
            Object... providedArgs) throws Exception {
​
        Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
        if (logger.isTraceEnabled()) {
            logger.trace("Arguments: " + Arrays.toString(args));
        }
        return doInvoke(args);
    }

org.springframework.web.method.support.InvocableHandlerMethod#getMethodArgumentValues

protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
            Object... providedArgs) throws Exception {
​
        MethodParameter[] parameters = getMethodParameters();
        if (ObjectUtils.isEmpty(parameters)) {
            return EMPTY_ARGS;
        }
        //这个是解析method里面的参数，而不是url后面的参数
        Object[] args = new Object[parameters.length];
        for (int i = 0; i < parameters.length; i++) {
            MethodParameter parameter = parameters[i];
            parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
            args[i] = findProvidedArgument(parameter, providedArgs);
            if (args[i] != null) {
                continue;
            }
            //支持26种参数解析，这里会通过缓存获取，大大提高效率
            if (!this.resolvers.supportsParameter(parameter)) {
                throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));
            }
            try {
                args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
            }
            

//注意这里都会从缓存中去获取参数，提高效率

org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver#resolveArgument

public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
            NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
​
        NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);
        MethodParameter nestedParameter = parameter.nestedIfOptional();
​
        Object resolvedName = resolveEmbeddedValuesAndExpressions(namedValueInfo.name);
        if (resolvedName == null) {
            throw new IllegalArgumentException(
                    "Specified name must not resolve to null: [" + namedValueInfo.name + "]");
        }
​
        Object arg = resolveName(resolvedName.toString(), nestedParameter, webRequest);
        if (arg == null) {
            //是否有默认参数
            if (namedValueInfo.defaultValue != null) {
                arg = resolveEmbeddedValuesAndExpressions(namedValueInfo.defaultValue);
            }
            //是否必须
            else if (namedValueInfo.required && !nestedParameter.isOptional()) {
                handleMissingValue(namedValueInfo.name, nestedParameter, webRequest);
            }
            //处理null
            arg = handleNullValue(namedValueInfo.name, arg, nestedParameter.getNestedParameterType());
        }
        else if ("".equals(arg) && namedValueInfo.defaultValue != null) {
            arg = resolveEmbeddedValuesAndExpressions(namedValueInfo.defaultValue);
        }
​
        if (binderFactory != null) {
            WebDataBinder binder = binderFactory.createBinder(webRequest, null, namedValueInfo.name);
            try {
            //进行参数转换
                arg = binder.convertIfNecessary(arg, parameter.getParameterType(), parameter);
            }
            catch (ConversionNotSupportedException ex) {
                throw new MethodArgumentConversionNotSupportedException(arg, ex.getRequiredType(),
                        namedValueInfo.name, parameter, ex.getCause());
            }
            catch (TypeMismatchException ex) {
                throw new MethodArgumentTypeMismatchException(arg, ex.getRequiredType(),
                        namedValueInfo.name, parameter, ex.getCause());
            }
        }
​
        handleResolvedValue(arg, namedValueInfo.name, parameter, mavContainer, webRequest);
​
        return arg;
    }

注意参数的三大属性：name required defaultValue

org.springframework.web.method.annotation.RequestParamMethodArgumentResolver#resolveName

处理url后面的参数

protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest request) throws Exception {
        HttpServletRequest servletRequest = request.getNativeRequest(HttpServletRequest.class);
​
        if (servletRequest != null) {
            Object mpArg = MultipartResolutionDelegate.resolveMultipartArgument(name, parameter, servletRequest);
            if (mpArg != MultipartResolutionDelegate.UNRESOLVABLE) {
                return mpArg;
            }
        }
​
        Object arg = null;
        //判断是否文件请求
        MultipartRequest multipartRequest = request.getNativeRequest(MultipartRequest.class);
        if (multipartRequest != null) {
            List<MultipartFile> files = multipartRequest.getFiles(name);
            if (!files.isEmpty()) {
                arg = (files.size() == 1 ? files.get(0) : files);
            }
        }
        if (arg == null) {
        //获取请求url的参数，核心的代码
            String[] paramValues = request.getParameterValues(name);
            if (paramValues != null) {
                arg = (paramValues.length == 1 ? paramValues[0] : paramValues);
            }
        }
        return arg;
    }