本文章介绍如何利用SQL中的系统存储过程SP_OA来执行对外部HTTP服务的请求，并处理返回的数据。适合需要在数据库层直接操作网络接口的开发者阅读和学习。
```sql
DECLARE @Object int;
DECLARE @HR int;
DECLARE @Property nvarchar(255);
DECLARE @Return nvarchar(255);
DECLARE @Source nvarchar(255), @Desc nvarchar(255);
DECLARE @httpStatus int;
DECLARE @response varchar(8000);
-- 创建 OLE 对象的实例
EXEC @HR = sp_OACreate MSXML2.XMLHTTP.6.0,@Object OUT;
IF @HR <> 0
BEGIN
EXEC sp_OAGetErrorInfo @Object,@Source OUT,@Desc OUT;
RAISERROR(Error Creating COM Component %x, %s, %s,16,1, @HR, @Source, @Desc);
GOTO END_ROUTINE
END
-- 打开连接
EXEC @HR = sp_OAMethod @Object,open,GET,http://localhost:1728/HttpServer/submit.aspx,FALSE;
IF @HR <> 0
BEGIN
EXEC sp_OAGetErrorInfo @Object,@Source OUT,@Desc OUT;
RAISERROR(Open %x, %s, %s,16,1, @HR, @Source, @Desc);
GOTO CLEANUP
END
-- 设置请求头
EXEC @HR = sp_OAMethod @Object,setRequestHeader,Content-Type,text/xml;
IF @HR <> 0
BEGIN
EXEC sp_OAGetErrorInfo @Object,@Source OUT,@Desc OUT;
RAISERROR(setRequestHeader %x, %s, %s,16,1, @HR, @Source, @Desc);
GOTO CLEANUP
END
-- 发送请求
EXEC @HR = sp_OAMethod @Object,send;
IF @HR <> 0
BEGIN
EXEC sp_OAGetErrorInfo @Object,@Source OUT,@Desc OUT;
RAISERROR(send %x, %s, %s,16,1, @HR, @Source, @Desc);
GOTO CLEANUP
END
-- 获取 readyState 属性值
EXEC @HR = sp_OAGetProperty @Object,readyState,@httpStatus OUT;
IF @HR <> 0
BEGIN
EXEC sp_OAGetErrorInfo @Object,@Source OUT,@Desc OUT;
RAISERROR(readyState %x, %s, %s,16,1, @HR, @Source, @Desc);
GOTO CLEANUP
END
-- 验证 readyState 是否为 4（表示请求完成）
IF @httpStatus <> 4
BEGIN
RAISERROR(readyState http status bad,16,1);
GOTO CLEANUP
END
-- 获取 HTTP 状态码
EXEC @HR = sp_OAGetProperty @Object,status,@httpStatus OUT;
IF @HR <> 0
BEGIN
EXEC sp_OAGetErrorInfo @Object,@Source OUT,@Desc OUT;
RAISERROR(getstatus %x, %s, %s,16,1, @HR, @Source, @Desc);
GOTO CLEANUP
END
-- 验证 HTTP 状态码是否为 200（表示请求成功）
IF @httpStatus <> 200
BEGIN
PRINT CAST(@httpStatus AS varchar);
RAISERROR(Open http status bad,16,1);
GOTO CLEANUP
END
-- 获取响应文本
EXEC @HR = sp_OAGetProperty @Object,responseText,@response OUT;
IF @HR <> 0
BEGIN
EXEC sp_OAGetErrorInfo @Object,@Source OUT,@Desc OUT;
RAISERROR(responseText %x, %s, %s,16,1, @HR, @Source, @Desc);
GOTO CLEANUP
END
PRINT @response;
CLEANUP:
BEGIN
EXEC @HR = sp_OADestroy @Object;
IF @HR <> 0
BEGIN
EXEC sp_OAGetErrorInfo @Object,@Source OUT,@Desc OUT;
SELECT HR = convert(varbinary(4),@HR),
Source=@Source,
Description=@Desc;
END
END
END_ROUTINE:
RETURN;
```
这段代码使用了SQL Server的sp_OA系列存储过程来创建和操作COM对象，通过`MSXML2.XMLHTTP.6.0` COM组件实现了一个简单的HTTP请求，并对可能产生的错误进行了详细的处理。
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