123.【SpringBoot 源码刨析B】（七）

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

// Actually invoke the handler.
//DispatcherServlet -- doDispatch
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

// RequestMappingHandlerAdapter 类
mav = invokeHandlerMethod(request, response, handlerMethod); //执行目标方法
//ServletInvocableHandlerMethod 类
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
//InvocableHandlerMethod 类 获取方法的参数值
Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);

============InvocableHandlerMethod 类种   ==========================
protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
      Object... providedArgs) throws Exception {
    MethodParameter[] parameters = getMethodParameters();
    if (ObjectUtils.isEmpty(parameters)) {
      return EMPTY_ARGS;
    }
    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;
      }
      if (!this.resolvers.supportsParameter(parameter)) {
        throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));
      }
      try {
        args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
      }
      catch (Exception ex) {
        // Leave stack trace for later, exception may actually be resolved and handled...
        if (logger.isDebugEnabled()) {
          String exMsg = ex.getMessage();
          if (exMsg != null && !exMsg.contains(parameter.getExecutable().toGenericString())) {
            logger.debug(formatArgumentError(parameter, exMsg));
          }
        }
        throw ex;
      }
    }
    return args;
  }

HandlerMethodArgumentResolverComposite 类
  @Nullable
  private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
    HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
    if (result == null) {
      for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) {
        if (resolver.supportsParameter(parameter)) {
          result = resolver;
          this.argumentResolverCache.put(parameter, result);
          break;
        }
      }
    }
    return result;
  }

InvocableHandlerMethod 类 进入这个方法
args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
调用各自 HandlerMethodArgumentResolver 的 resolveArgument 方法即可

BeanUtils  类
  /**
   * Check if the given type represents a "simple" value type: a primitive or
   * primitive wrapper, an enum, a String or other CharSequence, a Number, a
   * Date, a Temporal, a URI, a URL, a Locale, or a Class.
   * <p>{@code Void} and {@code void} are not considered simple value types.
   * @param type the type to check
   * @return whether the given type represents a "simple" value type
   * @see #isSimpleProperty(Class)
   */
  public static boolean isSimpleValueType(Class<?> type) {
    return (Void.class != type && void.class != type &&
        (ClassUtils.isPrimitiveOrWrapper(type) ||
        Enum.class.isAssignableFrom(type) ||
        CharSequence.class.isAssignableFrom(type) ||
        Number.class.isAssignableFrom(type) ||
        Date.class.isAssignableFrom(type) ||
        Temporal.class.isAssignableFrom(type) ||
        URI.class == type ||
        URL.class == type ||
        Locale.class == type ||
        Class.class == type));
  }

@Override
  @Nullable
  public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
      NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
    Assert.state(mavContainer != null, "ModelAttributeMethodProcessor requires ModelAndViewContainer");
    Assert.state(binderFactory != null, "ModelAttributeMethodProcessor requires WebDataBinderFactory");
    String name = ModelFactory.getNameForParameter(parameter);
    ModelAttribute ann = parameter.getParameterAnnotation(ModelAttribute.class);
    if (ann != null) {
      mavContainer.setBinding(name, ann.binding());
    }
    Object attribute = null;
    BindingResult bindingResult = null;
    if (mavContainer.containsAttribute(name)) {
      attribute = mavContainer.getModel().get(name);
    }
    else {
      // Create attribute instance
      try {
        attribute = createAttribute(name, parameter, binderFactory, webRequest);
      }
      catch (BindException ex) {
        if (isBindExceptionRequired(parameter)) {
          // No BindingResult parameter -> fail with BindException
          throw ex;
        }
        // Otherwise, expose null/empty value and associated BindingResult
        if (parameter.getParameterType() == Optional.class) {
          attribute = Optional.empty();
        }
        bindingResult = ex.getBindingResult();
      }
    }
    if (bindingResult == null) {
      // Bean property binding and validation;
      // skipped in case of binding failure on construction.
      // 类型转换器
  ⭐   WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);
      if (binder.getTarget() != null) {
        if (!mavContainer.isBindingDisabled(name)) {
      // 开始赋值和转换    
  ⭐⭐        bindRequestParameters(binder, webRequest);
        }
        validateIfApplicable(binder, parameter);
        if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
          throw new BindException(binder.getBindingResult());
        }
      }
      // Value type adaptation, also covering java.util.Optional
      if (!parameter.getParameterType().isInstance(attribute)) {
        attribute = binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter);
      }
      bindingResult = binder.getBindingResult();
    }
    // Add resolved attribute and BindingResult at the end of the model
    Map<String, Object> bindingResultModel = bindingResult.getModel();
    mavContainer.removeAttributes(bindingResultModel);
    mavContainer.addAllAttributes(bindingResultModel);
    return attribute;
  }