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[DotnetCore]ORM系列-Chloe:Interceptor篇

前提情要

筆者前篇介紹Select相關的method[DotnetCore]ORM系列-Chloe:Select篇,這次要來寫interceptor,觀察看看那些select method對應的sql語法,才會知道Chloe都幫我們轉成什麼語法,才不會誤用造成錯誤,筆者覺得是值得投資的。

內容

Interceptor介紹

筆者這邊稍微解釋一下Interceptor,它要實作對應的六個Method,主要分法是照著DBCommand下的方法

  • ExecuteReader
  • ExecuteNonQuery
  • ExecuteScalar

針對這三個DbCommand下的這三個Method,Chloe規劃有執行前跟執行後的事件對應的Method,因此有六個Method可以實作。筆者寫的上篇都是Query,屬於ExecuteReader部份,只要撰寫

  • ReaderExecuting
  • ReaderExecuted

這兩個Method,其他的就先維持預設的「throw new NotImplementedException();」,另外wiki中也示範另一個重點是「DataBag」的概念,他是用key、value的方式設定,可以於不同事件method中交換資料,感覺很像mvc網站中的ViewBag、ViewData。範例中是示範ReaderExecuting中設定好startTime參數、ReaderExecuted中讀出startTime參數,與現在時間做比較,算出sql執行時間並印出來。

實作Interceptor

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public class DbCommandInterceptor : IDbCommandInterceptor
{
public void NonQueryExecuted(IDbCommand command, DbCommandInterceptionContext<int> interceptionContext)
{
throw new NotImplementedException();
}

public void NonQueryExecuting(IDbCommand command, DbCommandInterceptionContext<int> interceptionContext)
{
throw new NotImplementedException();
}

/* 执行 DbCommand.ExecuteReader() 时调用 */
public void ReaderExecuting(IDbCommand command, DbCommandInterceptionContext<IDataReader> interceptionContext)
{
interceptionContext.DataBag.Add("startTime", DateTime.Now);
Console.WriteLine(command.CommandText);
}
/* 执行 DbCommand.ExecuteReader() 后调用 */
public void ReaderExecuted(IDbCommand command, DbCommandInterceptionContext<IDataReader> interceptionContext)
{
DateTime startTime = (DateTime)(interceptionContext.DataBag["startTime"]);
Console.WriteLine(DateTime.Now.Subtract(startTime).TotalMilliseconds);
if (interceptionContext.Exception == null)
Console.WriteLine(interceptionContext.Result.FieldCount);
}

public void ScalarExecuted(IDbCommand command, DbCommandInterceptionContext<object> interceptionContext)
{
throw new NotImplementedException();
}

public void ScalarExecuting(IDbCommand command, DbCommandInterceptionContext<object> interceptionContext)
{
throw new NotImplementedException();
}
}

註冊Interceptor

要調整一下之前註冊IDbContext的地方

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services.AddScoped<ChloeORM.IDbContext>((serviceProvider) =>
{
var dbContext = new ChloeORM.MySql.MySqlContext(
new MySqlConnectionFactory(Configuration.GetConnectionString("ClassicModels")));
dbContext.Session.AddInterceptor(new DbCommandInterceptor());
return dbContext;
});

調用結果

筆者以上篇為例,貼出CustomerService,以註解的方式填寫對應的sql指令

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public class CustomerService : ICustomerService
{
private readonly IDbContext _db;

public CustomerService(IDbContext db)
{
_db = db;
}

public Customers GetCustomerById(int customerNumber)
{
// LIMIT部份不同資料庫會有不同的宣告
/*
SELECT
`Customers`.`CustomerNumber` AS `CustomerNumber`,
`Customers`.`CustomerName` AS `CustomerName`,
`Customers`.`ContactLastName` AS `ContactLastName`,
`Customers`.`ContactFirstName` AS `ContactFirstName`,
`Customers`.`Phone` AS `Phone`,
`Customers`.`AddressLine1` AS `AddressLine1`,
`Customers`.`AddressLine2` AS `AddressLine2`,
`Customers`.`City` AS `City`,
`Customers`.`State` AS `State`,
`Customers`.`PostalCode` AS `PostalCode`,
`Customers`.`Country` AS `Country`,
`Customers`.`SalesRepEmployeeNumber` AS `SalesRepEmployeeNumber`,
`Customers`.`CreditLimit` AS `CreditLimit`
FROM
`Customers` AS `Customers`
WHERE
`Customers`.`CustomerNumber` = ?P_0
LIMIT
0, 1
*/
return _db.Query<Customers>()
.FirstOrDefault(x => x.CustomerNumber == customerNumber);
}

public IEnumerable<Customers> GetCustomerListByLikeConditions(CustomerLikeConditions conditions)
{
/*
SELECT
`Customers`.`CustomerNumber` AS `CustomerNumber`,
`Customers`.`CustomerName` AS `CustomerName`,
`Customers`.`ContactLastName` AS `ContactLastName`,
`Customers`.`ContactFirstName` AS `ContactFirstName`,
`Customers`.`Phone` AS `Phone`,
`Customers`.`AddressLine1` AS `AddressLine1`,
`Customers`.`AddressLine2` AS `AddressLine2`,
`Customers`.`City` AS `City`,
`Customers`.`State` AS `State`,
`Customers`.`PostalCode` AS `PostalCode`,
`Customers`.`Country` AS `Country`,
`Customers`.`SalesRepEmployeeNumber` AS `SalesRepEmployeeNumber`,
`Customers`.`CreditLimit` AS `CreditLimit`
FROM
`Customers` AS `Customers`
WHERE
`Customers`.`CustomerName` LIKE CONCAT(?P_0, '%')
*/
return _db.Query<Customers>()
.Where(x => x.CustomerName.StartsWith(conditions.CustomerName))
.ToList();
}

public IEnumerable<Customers> GetCustomersListByInConditions(CustomerInConditions conditions)
{
/*
SELECT
`Customers`.`CustomerNumber` AS `CustomerNumber`,
`Customers`.`CustomerName` AS `CustomerName`,
`Customers`.`ContactLastName` AS `ContactLastName`,
`Customers`.`ContactFirstName` AS `ContactFirstName`,
`Customers`.`Phone` AS `Phone`,
`Customers`.`AddressLine1` AS `AddressLine1`,
`Customers`.`AddressLine2` AS `AddressLine2`,
`Customers`.`City` AS `City`,
`Customers`.`State` AS `State`,
`Customers`.`PostalCode` AS `PostalCode`,
`Customers`.`Country` AS `Country`,
`Customers`.`SalesRepEmployeeNumber` AS `SalesRepEmployeeNumber`,
`Customers`.`CreditLimit` AS `CreditLimit`
FROM
`Customers` AS `Customers`
WHERE
`Customers`.`CustomerName` IN (?P_0, ?P_1, ?P_2)
*/
return _db.Query<Customers>()
.Where(x => conditions.CustomerNameList.Contains(x.CustomerName))
.ToList();
}

public IEnumerable<Customers> GetCustomersListByPaginationConditions(CustomerPageConditions conditions)
{
/*
SELECT
`Customers`.`CustomerNumber` AS `CustomerNumber`,
`Customers`.`CustomerName` AS `CustomerName`,
`Customers`.`ContactLastName` AS `ContactLastName`,
`Customers`.`ContactFirstName` AS `ContactFirstName`,
`Customers`.`Phone` AS `Phone`,
`Customers`.`AddressLine1` AS `AddressLine1`,
`Customers`.`AddressLine2` AS `AddressLine2`,
`Customers`.`City` AS `City`,
`Customers`.`State` AS `State`,
`Customers`.`PostalCode` AS `PostalCode`,
`Customers`.`Country` AS `Country`,
`Customers`.`SalesRepEmployeeNumber` AS `SalesRepEmployeeNumber`,
`Customers`.`CreditLimit` AS `CreditLimit`
FROM
`Customers` AS `Customers`
ORDER BY
`Customers`.`CustomerName` ASC,
`Customers`.`CustomerNumber` ASC
LIMIT
0, 10
*/
return _db.Query<Customers>()
.OrderBy(x => x.CustomerName)
.ThenBy(x => x.CustomerNumber)
.TakePage(conditions.PageNumber, conditions.PageSize)
.ToList();
}

public List<string> GetCustomersCountryListByDistinct()
{
// SELECT DISTINCT `Customers`.`Country` AS `C` FROM `Customers` AS `Customers`
return _db.Query<Customers>()
.Select(x => x.Country)
.Distinct()
.ToList();
}

public IEnumerable<Customers> GetCustomersListByExists(CustomerExistConditions conditions)
{
/*
SELECT
`Customers`.`CustomerNumber` AS `CustomerNumber`,
`Customers`.`CustomerName` AS `CustomerName`,
`Customers`.`ContactLastName` AS `ContactLastName`,
`Customers`.`ContactFirstName` AS `ContactFirstName`,
`Customers`.`Phone` AS `Phone`,
`Customers`.`AddressLine1` AS `AddressLine1`,
`Customers`.`AddressLine2` AS `AddressLine2`,
`Customers`.`City` AS `City`,
`Customers`.`State` AS `State`,
`Customers`.`PostalCode` AS `PostalCode`,
`Customers`.`Country` AS `Country`,
`Customers`.`SalesRepEmployeeNumber` AS `SalesRepEmployeeNumber`,
`Customers`.`CreditLimit` AS `CreditLimit`
FROM
`Customers` AS `Customers`
WHERE
Exists (
SELECT
?P_0 AS `C`
FROM
`Customers` AS `Customers0`
WHERE
(
`Customers0`.`Country` = ?P_1
AND `Customers0`.`CustomerNumber` = `Customers`.`CustomerNumber`
)
)
*/
return _db.Query<Customers>()
.Where(x => _db.Query<Customers>()
.Where(c => c.Country == conditions.CountryName
&& c.CustomerNumber == x.CustomerNumber)
.Any())
.ToList();
}
}

以上,筆者需要解釋的就是?P_0?P_1等,應該就是會使用sql parameter對應的參數,其他的應該都看得懂,相較於EFcore產出的sql,Chloe產出的還算看得懂。

結論

畢竟Chloe套件本身也只是利用Extension及Expression解析,包裝成方便使用的linq形式存取對應的資料表,就像使用EFCore時因應效能上的考量,需要知道EFCore幫我們做了哪些事一樣,使用類似的ORM套件時,一開始使用,需要了解它底層幫我們做了什麼事是可以避免誤用的,筆者覺得是值得把時間投資在上面的。