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<Person> 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<Flux<T>>，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<Flux<T>>
      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<Integer> intList, List<Person> personList,
                         Set<Integer> intSet, Set<Person> personSet,
                         Map<String, Object> 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;
}