Spring MVC源码解析之HandlerMethod、ServletInvocableHandlerMethod

public class InvocableHandlerMethod extends HandlerMethod {
	private static final Object[] EMPTY_ARGS = new Object[0];

	// 新增属性：数据绑定、数据校验

	// 用于产生数据绑定器、校验器
	@Nullable
	private WebDataBinderFactory dataBinderFactory;
	// HandlerMethodArgumentResolver用于入参的解析
	private HandlerMethodArgumentResolverComposite resolvers = new HandlerMethodArgumentResolverComposite();
	// 获取到形参名,所以注解里我们不写value，通过形参名字来匹配也可以
	private ParameterNameDiscoverer parameterNameDiscoverer = new DefaultParameterNameDiscoverer();

public Object invokeForRequest(NativeWebRequest request, ModelAndViewContainer mavContainer,
		Object... providedArgs) throws Exception {

	Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
	}
	// 普通的方法调用
	Object returnValue = doInvoke(args);
	return returnValue;
}

public class ServletInvocableHandlerMethod extends InvocableHandlerMethod {
	private static final Method CALLABLE_METHOD = ClassUtils.getMethod(Callable.class, "call");

	// 处理方法返回值
	@Nullable
	private HandlerMethodReturnValueHandlerComposite returnValueHandlers;

	// 构造函数略
	
	// 设置处理返回值的HandlerMethodReturnValueHandler
	public void setHandlerMethodReturnValueHandlers(HandlerMethodReturnValueHandlerComposite returnValueHandlers) {
		this.returnValueHandlers = returnValueHandlers;
	}

	public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception {
		Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
		// 设置返回状态码 这里面还是有点意思的  因为@ResponseStatus#code()在父类已经解析,但子类才用
		setResponseStatus(webRequest);

		if (returnValue == null) {
			// Request的NotModified为true 有@ResponseStatus注解标注 RequestHandled=true 三个条件有一个成立,则设置请求处理完成并返回
			if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
				// 该请求已被处理
				mavContainer.setRequestHandled(true);
				return;
			}
		// 返回值不为null,@ResponseStatus存在reason 同样设置请求处理完成并返回
		} else if (StringUtils.hasText(getResponseStatusReason())) {
			mavContainer.setRequestHandled(true);
			return;
		}

		// 前边都不成立,则设置RequestHandled=false即请求未完成
		// 继续交给HandlerMethodReturnValueHandlerComposite处理
		mavContainer.setRequestHandled(false);
		Assert.state(this.returnValueHandlers != null, "No return value handlers");
		try {
			this.returnValueHandlers.handleReturnValue(returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
		}
		...
	}

	// 设置返回的状态码到HttpServletResponse 里面去
	private void setResponseStatus(ServletWebRequest webRequest) throws IOException {
		HttpStatus status = getResponseStatus();
		if (status == null) { // 如果调用者没有标注ResponseStatus.code()此注解  此处就忽略它
			return;
		}

		HttpServletResponse response = webRequest.getResponse();
		if (response != null) {
			String reason = getResponseStatusReason();

			// 此处务必注意：若有reason，那就是sendError  哪怕你是200哦~
			if (StringUtils.hasText(reason)) {
				response.sendError(status.value(), reason);
			} else {
				response.setStatus(status.value());
			}
		}

		// 设置到request的属性，把响应码给过去。为了在redirect中使用
		// To be picked up by RedirectView
		webRequest.getRequest().setAttribute(View.RESPONSE_STATUS_ATTRIBUTE, status);
	}

	private boolean isRequestNotModified(ServletWebRequest webRequest) {
		return webRequest.isNotModified();
	}


	// 这个方法RequestMappingHandlerAdapter里有调用
	ServletInvocableHandlerMethod wrapConcurrentResult(Object result) {
		return new ConcurrentResultHandlerMethod(result, new ConcurrentResultMethodParameter(result));
	}

	// 内部类们
	private class ConcurrentResultMethodParameter extends HandlerMethodParameter {
		@Nullable
		private final Object returnValue;
		private final ResolvableType returnType;
		public ConcurrentResultMethodParameter(Object returnValue) {
			super(-1);
			this.returnValue = returnValue;
			// 主要是这个解析 兼容到了泛型类型 比如你的返回值是List 它也能把你的类型拿出来
			this.returnType = (returnValue instanceof ReactiveTypeHandler.CollectedValuesList ?
					((ReactiveTypeHandler.CollectedValuesList) returnValue).getReturnType() :
					ResolvableType.forType(super.getGenericParameterType()).getGeneric());
		}

		// 若返回的是List  这里就是List的类型哦  下面才是返回泛型类型
		@Override
		public Class<?> getParameterType() {
			if (this.returnValue != null) {
				return this.returnValue.getClass();
			}
			if (!ResolvableType.NONE.equals(this.returnType)) {
				return this.returnType.toClass();
			}
			return super.getParameterType();
		}

		// 返回泛型类型
		@Override
		public Type getGenericParameterType() {
			return this.returnType.getType();
		}


		// 即使实际返回类型为ResponseEntity>，也要确保对@ResponseBody-style处理从reactive 类型中收集值
		// 是对reactive 的一种兼容
		@Override
		public <T extends Annotation> boolean hasMethodAnnotation(Class<T> annotationType) {
			// Ensure @ResponseBody-style handling for values collected from a reactive type
			// even if actual return type is ResponseEntity>
			return (super.hasMethodAnnotation(annotationType) ||
					(annotationType == ResponseBody.class && this.returnValue instanceof ReactiveTypeHandler.CollectedValuesList));
		}
	}


	// 这个非常有意思   内部类继承了自己（外部类） 进行增强
	private class ConcurrentResultHandlerMethod extends ServletInvocableHandlerMethod {
		// 返回值
		private final MethodParameter returnType;

		// 此构造最终传入的handler是个Callable
		// result方法返回值 它支持支持异常调用结果处理
		public ConcurrentResultHandlerMethod(final Object result, ConcurrentResultMethodParameter returnType) {
			super((Callable<Object>) () -> {
				if (result instanceof Exception) {
					throw (Exception) result;
				} else if (result instanceof Throwable) {
					throw new NestedServletException("Async processing failed", (Throwable) result);
				}
				return result;
			}, CALLABLE_METHOD);


			// 给外部类把值设置上  因为wrapConcurrentResult一般都先调用，是对本类的一个增强
			if (ServletInvocableHandlerMethod.this.returnValueHandlers != null) {
				setHandlerMethodReturnValueHandlers(ServletInvocableHandlerMethod.this.returnValueHandlers);
			}
			this.returnType = returnType;
		}
		...
	}
}

@NotNull
private String name;
@NotNull
@Positive
private Integer age;

public Object demoMethod(Person person, Object object,
                         List intList, List personList,
                         Set intSet, Set personSet,
                         Map myMap,
                         String name, Integer age,
                         int number, double money) {
    return "hello parameter";
}

public static void main(String[] args) {
    // 准备一个HandlerMethod
    HandlerMethod handlerMethod = new HandlerMethod(new Person(), getPersonSpecfyMethod());
    // 拿到该方法所有的参数
    MethodParameter[] methodParameters = handlerMethod.getMethodParameters();
    for (MethodParameter parameter : methodParameters) {
        Class parameterType = parameter.getParameterType();
        String nameForParameter = ModelFactory.getNameForParameter(parameter);
        System.out.println("类型" + parameterType.getName() + "--->缺省的modelKey是：" + nameForParameter);
    }
}

private static Method getPersonSpecfyMethod() {
    for (Method method : Person.class.getMethods())
        if (method.getName().equals("demoMethod"))
            return method;
    return null;
}