sql server 2005中新增加的try catch,可以很容易捕捉异常了,今天大概学习看了下,归纳下要点如下
基本用法BEGIN TRY
{ sql_statement |
statement_block }
END TRY
BEGIN CATCH
{ sql_statement |
statement_block }
END CATCH
,和普通语言的异常处理用法差不多,但要注意的是,SQL SERVER只捕捉那些不是严重的异常,当比如数据库不能连接等这类异常时,是不能捕捉的一个例子:BEGIN TRY
DECLARE @X INT
-- Divide by zero to generate Error
SET @X = 1/0
PRINT 'Command after error in TRY block'
END TRY
BEGIN CATCH
PRINT 'Error Detected'
END CATCH
PRINT 'Command after TRY/CATCH blocks'
另外try catch可以嵌套Begin TRY
delete from GrandParent where Name = 'John Smith'
print 'GrandParent deleted successfully'
End Try
Begin Catch
Print 'Error Deleting GrandParent Record'
Begin Try
delete from Parent where GrandParentID =
(select distinct ID from GrandParent where Name = 'John Smith')
Print 'Parent Deleted Successfully'
End Try
Begin Catch
print 'Error Deleting Parent'
Begin Try
delete from child where ParentId =
(select distinct ID from Parent where GrandParentID =
(select distinct ID from GrandParent where Name = 'John Smith'))
print 'Child Deleted Successfully'
End Try
Begin Catch
Print 'Error Deleting Child'
End Catch
End Catch
End Catch
另外,SQL SERVER 2005在异常机制中,提供了error类的方法方便调试,现摘抄如下,比较简单,不予以解释ERROR_NUMBER(): Returns a number associated with the error.ERROR_SEVERITY(): Returns the severity of the error.ERROR_STATE(): Returns the error state number associated with the error.ERROR_PROCEDURE(): Returns the name of the stored procedure or trigger in which the error occurred.ERROR_LINE(): Returns the line number inside the failing routine that caused the error. ERROR_MESSAGE(): Returns the complete text of the error message. The text includes the values supplied for any substitutable parameters, such as lengths, object names, or times. 最后举例子如下,使用了error类的方法BEGIN TRY

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选择DependencyInjection(DI)用于大型应用,ServiceLocator适合小型项目或原型。1)DI通过构造函数注入依赖,提高代码的测试性和模块化。2)ServiceLocator通过中心注册获取服务,方便但可能导致代码耦合度增加。

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