Question

在我的REST API服务层中，我有一个ProductService类我的所有函数中都存在以下逻辑：Do Validate，如果验证失败，我会抛出无效异常，如果通过，我会继续执行下一个try-catch并在发生故障时抛出一般错误：

def addProduct(request:AddProductRequest): BaseResponse[String] = 
{
  try
  {
      request.validate
  }
  catch
  {
     case ex: Exception => {
       Logger.error("Failed to add product, Validation failed", ex);
       val errorResponse:ErrorResponse[String] = new ErrorResponseList().InvalidParameters
       errorResponse.addMessage(ex.getMessage)
       return errorResponse
     }
  }

  try
  {
      val addedProductId = productRepository.addProduct(request.language, request.tenantId, request.product)
      DTOResponse(addedProductId)      
  }
  catch
  {    
     case ex: Exception => {
       Logger.error("Failed to add product to tenant Id="+request.tenantId+" language="+request.language, ex);
       val errorResponse:ErrorResponse[String] = new ErrorResponseList().GeneralError
       errorResponse.addMessage(ex.getMessage())
       return errorResponse
     }
  }
}

现在，我没有使用相同的try和catch为所有函数重复request.validate，而是使用以下函数创建了一个基类：

abstract class ServiceBase {
def validate[T](request:BaseRequest)
{
  try
  {
    request.validate
  }
  catch
  {
    case ex: Exception => {
      Logger.error("Validation failed", ex);
      val errorResponse:ErrorResponse[String] = new ErrorResponseList().InvalidParameters
      errorResponse.addMessage(ex.getMessage)
      return errorResponse
    }
  }
}

现在，我的addProduct（..）将如下所示：

validate(request)
..the rest of the code - the 2nd try-catch

这可以节省很多行。

问题是如果验证失败，它将永远不会返回。我在ServiceBase中收到以下错误：

Multiple markers at this line
- enclosing method validate has result type Unit: return value discarded
- enclosing method validate has result type Unit: return value discarded
- a pure expression does nothing in statement position; you may be omitting necessary 
 parentheses

Answer 1

validate没有返回类型（因此默认返回Unit），ServiceBase validate的签名应如下所示：

def validate[T](request:BaseRequest): BaseResponse[String] =

（假设您要返回BaseResponse[String]）

Answer 2

这可能对某人有用，总有一天，函数编程..我们说^ _ ^

将ServiceBase验证更改为：

def validate[T](request:BaseRequest):Option[BaseResponse[T]] =
{
  try
  {
    request.validate
    None
  }
  catch
  {
    case ex: Exception => {
      Logger.error("Validation failed", ex);
      val errorResponse:ErrorResponse[T] = new ErrorResponseList().InvalidParameters
      errorResponse.addMessage(ex.getMessage)
      return Some(errorResponse)
    }
  }
}

现在我这样做：

def getProducts(request:GetProductsRequest) :BaseResponse[ProductSearchResults] = 
{      
  validate[ProductSearchResults](request).getOrElse(
      {
        try
        {
          val products = productRepository.getProducts(request.language,request.tenantId,request.productIds)
          val foundProducts = for (product <- products) yield  (product.id)
          val notFoundProducts = request.productIds filterNot (foundProducts.toSet)
          val responseWrapper = new ProductSearchResults(products, notFoundProducts)
          DTOResponse(responseWrapper)
        }
        catch
        {
          case ex: Exception => {
            Logger.error("Failed to get products from tenant Id="+request.tenantId+" language="+request.language, ex);
            val errorResponse:ErrorResponse[ProductSearchResults] = new ErrorResponseList().GeneralError
            errorResponse.addMessage(ex.getMessage())
            return errorResponse
            }
        }})
 }

从派生的基类返回/中断函数

2 个答案: