ServiceStack服務請求設計

Question

我熱衷於使用ServiceStack，並使用簡單的客戶服務創建了一個小測試應用程序：

  [Route("/customers/{id}")]
    public class GetCustomer : IReturn<Customer>
    {
        public int Id { get; set; }
    }
    [Route("/customers/search")]
    public class FindCustomers : IReturn<List<Customer>>
    {
        public string LastName { get; set; }
        public int Age { get; set; }
        public string? City { get; set; }
    }

    public class CustomerService : IService
    {
        public object Get(GetCustomer request)
        {
            var db = new WebServDb();
            var customer = db.FirstOrDefault<Customer>("WHERE Id=@0", request.Id);
            return customer;
        }
        public object Get(FindCustomers request)
        {
            var db = new WebServDb();
            var customers = new List<Customer>();
            if (request.City.HasValue)
                customers = db.Fetch<Customer>("WHERE LastName=@0 AND Age=@1 AND City=@2", request.LastName, request.Age, request.City);
            else
                customers = db.Fetch<Customer>("WHERE LastName=@0 AND Age=@1", request.LastName, request.Age);
            return customers;
        }
    }

FindCustomers請求DTO包含3個可用於搜索客戶的屬性。 根據設置的屬性，我需要以不同的方式查詢數據庫。 那么最好的方法是什么？ 例如，如果我添加另一個屬性，例如：

 [Route("/customers/search")]
    public class FindCustomers : IReturn<List<Customer>>
    {
        public string LastName { get; set; }
        public int Age { get; set; }
        public string? City { get; set; }
        public string? ZipCode { get; set; }
    }

到FindCustomers DTO，我還必須將服務的Get方法更改為：

public object Get(FindCustomers request)
{
    var db = new WebServDb();
    var customers = new List<Customer>();
    if (request.City.HasValue && request.ZipCode.HasValue)
       customers = db.Fetch<Customer>("WHERE LastName=@0 AND Age=@1 AND City=@2 AND ZipCode=@3", request.LastName, request.Age, request.City, request.ZipCode);
    else if (request.City.HasValue)
       customers = db.Fetch<Customer>("WHERE LastName=@0 AND Age=@1 AND City=@2", request.LastName, request.Age, request.City);
    else
       customers = db.Fetch<Customer>("WHERE LastName=@0 AND Age=@1", request.LastName, request.Age);
    return customers;
  }

因此，對於我從請求DTO添加/刪除的每個屬性，我都需要修改Get方法。 有更好的方法嗎？ 檢查屬性集和查詢數據庫的更通用方法？

它會更好有具體要求的DTO如FindCustomersByLastNameCity，FindCustomersByLastNameZipCode，等，以及在相應的CustomerService具體Get方法？

Answer 1

最好有特定的請求DTO，例如FindCustomersByLastNameCity，FindCustomersByLastNameZipCode
如果可能的話，我會避免這樣做，因為這違反了ServiceStack鼓勵的“基於消息的服務”的好處/方法。

有更好的方法嗎？
我不知道我是否有“更好的方式”，但以下是我嘗試過的兩個選擇。 第二個選項仍然是“進行中的工作”，它的意思是“更抽象”，但我對其進行了修改，以配合您的示例並希望激發其他想法。

使用ExpressionVisitor的選項1：

public object Get(FindCustomers request)
{
    var customers = new List<Customer>();

    var ev = OrmLiteConfig.DialectProvider.ExpressionVisitor<Customer>();
    ev.Where(c => c.LastName == request.LastName).And(c => c.Age == request.Age);
    AddOptionalFilters(ev, request);

    customers = Db.Select<Customer>(ev);

    return customers;
}

private void AddOptionalFilters(SqlExpressionVisitor<Customer> expressionVisitor, FindCustomers request)
{
    if (request.City.HasValue)
    { expressionVisitor.Where(c => c.City == request.City); }

    if (request.ZipCode.HasValue)
    { expressionVisitor.Where(c => c.ZipCode == request.ZipCode); }
} 

使用Dapper的SqlBuilder的選項2：

public object Get(FindCustomers request)
{
    var customers = new List<Customer>();          

    var sqlAndParams = SqlAndParameters("SELECT * From Customers", request); //this returns a tuple of the sql string and the parameters
    customers = Db.Query<Customer>(sqlAndParams.Item1, sqlAndParams.Item2);

    return customers;
}

public virtual Tuple<String, IDictionary<string, object>> SqlAndParameters(string sql, FindCustomers request)
{
    var builder = new SqlBuilder();
    var selector = builder.AddTemplate(sql);
    var sqlParams = new ExpandoObject() as IDictionary<string, object>;

    builder.Where("LastName=@LastName");
    sqlParams.Add("LastName", request.LastName);

    builder.Where("Age=@Age");
    sqlParams.Add("Age", request.Age);

    if (request.City.HasValue)
    {
        builder.Where("City=@City");
        sqlParams.Add("City", request.City);
    }

    if (request.ZipCode.HasValue)
    {
        builder.Where("ZipCode=@ZipCode");
        sqlParams.Add("ZipCode", request.ZipCode);
    }

    return Tuple.Create(selector.RawSql, sqlParams);
}