设置大型数据（OLE DB）

2017-04-27

此示例演示如何设置 BLOB 数据、创建表、添加示例记录、提取行集中的记录，然后设置 BLOB 字段的值。 IA64 不支持此示例。

若要将指针传递给其自己的存储对象，使用者将创建一个访问器，该访问器绑定 BLOB 列的值，然后调用 IRowsetChange::SetData 或 IRowsetChange::InsertRow 方法。

此示例需要 AdventureWorks 示例数据库，可以从 Microsoft SQL Server 示例和社区项目主页下载该数据库。

重要

请尽可能使用 Windows 身份验证。如果 Windows 身份验证不可用，则提示用户在运行时输入其凭据。避免将凭据存储在文件中。如果必须保留凭据，则应使用 Win32 加密 API 对其进行加密。

过程

设置 BLOB 数据

创建描述如何访问 BLOB 列的 DBOBJECT 结构。将 DBOBJECT 结构的 dwFlag 元素设置为STGM_READ并将 iid 元素设置为 IID_ISequentialStream （要公开的接口）。
设置DBPROPSET_ROWSET属性组中的属性，以便行集可更新。
使用 DBBINDING 结构的数组创建一组绑定（每个列之一）。将 DBBINDING 结构中的 wType 元素设置为DBTYPE_IUNKNOWN， 并将 pObject 元素设置为指向创建的 DBOBJECT 结构。
使用结构 DBBINDINGS 数组中的绑定信息创建访问器。
调用 GetNextRows 以提取行集中的下一行。调用 GetData 以从行集中读取数据。
若要设置数据，请创建包含数据（以及长度指示器）的存储对象，然后使用绑定 BLOB 列的访问器调用 IRowsetChange::SetData （或 IRowsetChange::InsertRow）。

示例：

DESCRIPTION

使用 ole32.lib oleaut32.lib 进行编译，并执行以下C++代码列表。此应用程序连接到计算机的默认 SQL Server 实例。在某些 Windows作系统上，需要将（localhost）或（local）更改为 SQL Server 实例的名称。若要连接到命名实例，请将连接字符串从 L“（local）”更改为 L“（local）\\name”，其中名称为命名实例。默认情况下，SQL Server Express 安装到命名实例。请确保 INCLUDE 环境变量包含包含 sqlncli.h 的目录。

代码

// compile with: ole32.lib oleaut32.lib  
#define UNICODE  
#define DBINITCONSTANTS  
#define INITGID  
#define OLEDBVER 0x0250  // to include correct interfaces  
  
#include <windows.h>  
#include <stdio.h>  
#include <stddef.h>  
#include <iostream>  
#include <oledb.h>  
#include <oledberr.h>  
#include <SQLNCLI.h>  
  
using namespace std;  
  
#define SAFE_RELEASE(pIUnknown) if(pIUnknown) (pIUnknown)->Release();  
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown);  
HRESULT CreateTable(ICommandText* pICommandText);  
  
class CSeqStream : public ISequentialStream {  
public:  
   // Constructors  
   CSeqStream();  
   virtual ~CSeqStream();  
  
   virtual BOOL Seek(ULONG iPos);  
   virtual BOOL Clear();  
   virtual BOOL CompareData(void* pBuffer);  
   virtual ULONG Length() { return m_cBufSize; };  
  
   virtual operator void* const() { return m_pBuffer; };  
  
   STDMETHODIMP_(ULONG) AddRef(void);  
   STDMETHODIMP_(ULONG) Release(void);  
   STDMETHODIMP QueryInterface(REFIID riid, LPVOID *ppv);  
  
   STDMETHODIMP Read(   
      /* [out] */ void __RPC_FAR *pv,  
      /* [in]  */ ULONG cb,  
      /* [out] */ ULONG __RPC_FAR *pcbRead);  
  
   STDMETHODIMP Write(   
      /* [in] */ const void __RPC_FAR *pv,  
      /* [in] */ ULONG cb,  
      /* [out]*/ ULONG __RPC_FAR *pcbWritten);  
  
private:  
   ULONG m_cRef;   // reference count  
   void* m_pBuffer;   // buffer  
   ULONG m_cBufSize;   // buffer size  
   ULONG m_iPos;   // current index position in the buffer  
};  
  
// class implementation  
CSeqStream::CSeqStream() {  
   m_iPos = 0;  
   m_cRef = 0;  
   m_pBuffer = NULL;  
   m_cBufSize = 0;  
  
   // The constructor AddRef's  
   AddRef();  
}  
  
CSeqStream::~CSeqStream() {  
   // Shouldn't have any references left ASSERT(m_cRef == 0);  
   CoTaskMemFree(m_pBuffer);  
}  
  
ULONG CSeqStream::AddRef() {  
   return ++m_cRef;  
}  
  
ULONG CSeqStream::Release() {  
   // ASSERT(m_cRef);  
   if (--m_cRef)  
      return m_cRef;  
  
   delete this;  
   return 0;  
}  
  
HRESULT CSeqStream::QueryInterface(REFIID riid, void** ppv) {  
   // ASSERT(ppv);  
   *ppv = NULL;  
  
   if (riid == IID_IUnknown)  
      *ppv = this;  
  
   if (riid == IID_ISequentialStream)  
      *ppv = this;  
  
   if(*ppv) {  
      ((IUnknown*)*ppv)->AddRef();  
      return S_OK;  
   }  
  
   return E_NOINTERFACE;  
}  
  
BOOL CSeqStream::Seek(ULONG iPos) {  
   // Make sure the desired position is within the buffer  
   // ASSERT(iPos == 0 || iPos < m_cBufSize);  
  
   // Reset the current buffer position  
   m_iPos = iPos;  
   return TRUE;  
}  
  
BOOL CSeqStream::Clear() {  
   // Frees the buffer  
   m_iPos = 0;  
   m_cBufSize = 0;  
  
   CoTaskMemFree(m_pBuffer);  
   m_pBuffer = NULL;  
  
   return TRUE;  
}  
  
BOOL CSeqStream::CompareData(void* pBuffer) {  
   // ASSERT(pBuffer);  
  
   // Quick and easy way to compare user buffer with the stream  
   return memcmp(pBuffer, m_pBuffer, m_cBufSize) == 0;  
}  
  
HRESULT CSeqStream::Read(void *pv, ULONG cb, ULONG* pcbRead) {  
   // Parameter checking  
   if (pcbRead)  
      *pcbRead = 0;  
  
   if (!pv)  
      return STG_E_INVALIDPOINTER;  
  
   if (cb == 0)  
      return S_OK;  
  
   // Actual code  
   ULONG cBytesLeft = m_cBufSize - m_iPos;  
   ULONG cBytesRead = cb > cBytesLeft ? cBytesLeft : cb;  
  
   // if no more bytes to retrieve return   
   if (cBytesLeft == 0)  
      return S_FALSE;   
  
   // Copy to users buffer the number of bytes requested or remaining  
   memcpy(pv, (void*)((BYTE*)m_pBuffer + m_iPos), cBytesRead);  
   m_iPos += cBytesRead;  
  
   if (pcbRead)  
      *pcbRead = cBytesRead;  
  
   if (cb != cBytesRead)  
      return S_FALSE;   
  
   return S_OK;  
}  
  
HRESULT CSeqStream::Write(const void *pv, ULONG cb, ULONG* pcbWritten) {  
   // Parameter checking  
   if (!pv)  
      return STG_E_INVALIDPOINTER;  
  
   if (pcbWritten)  
      *pcbWritten = 0;  
  
   if (cb == 0)  
      return S_OK;  
  
   // Enlarge the current buffer  
   m_cBufSize += cb;  
  
   // Need to append to the end of the stream  
   m_pBuffer = CoTaskMemRealloc(m_pBuffer, m_cBufSize);  
   memcpy((void*)((BYTE*)m_pBuffer + m_iPos), pv, cb);  
   // m_iPos += cb;  
  
   if (pcbWritten)  
      *pcbWritten = cb;  
  
   return S_OK;  
}  
  
int main() {  
   CoInitialize(NULL);  
  
   DBOBJECT ObjectStruct;  
   ObjectStruct.dwFlags = STGM_READ;  
   ObjectStruct.iid = IID_ISequentialStream;  
  
   struct BLOBDATA {  
      DBSTATUS dwStatus;     
      DBLENGTH dwLength;   
      ISequentialStream* pISeqStream;  
   };  
  
   BLOBDATA BLOBGetData;  
   BLOBDATA BLOBSetData;  
  
   const ULONG cBindings = 1;  
   DBBINDING rgBindings[cBindings];   
   HRESULT hr = S_OK;  
  
   IAccessor* pIAccessor = NULL;  
   ICommandText* pICommandText = NULL;  
   ICommandProperties* pICommandProperties = NULL;  
   IRowsetChange* pIRowsetChange = NULL;  
   IRowset* pIRowset = NULL;  
   CSeqStream* pMySeqStream = NULL;  
  
   DBCOUNTITEM cRowsObtained = 0;  
   HACCESSOR hAccessor = DB_NULL_HACCESSOR;  
   DBBINDSTATUS rgBindStatus[cBindings];  
   HROW* rghRows = NULL;  
  
   const ULONG cPropSets = 1;  
   DBPROPSET rgPropSets[cPropSets];  
   const ULONG cProperties = 1;  
   DBPROP rgProperties[cProperties];  
   const ULONG cBytes = 10;  
  
   BYTE pBuffer[cBytes];  
   ULONG cBytesRead = 0;  
  
   BYTE pReadData[cBytes];   // read BLOB data in this array  
   memset(pReadData, 0xAA, cBytes);  
  
   BYTE pWriteData[cBytes];   // write BLOB data from this array  
   memset(pWriteData, 'D', cBytes);  
  
   // Get Command object  
   hr = GetCommandObject(IID_ICommandText, (IUnknown**)&pICommandText);  
   if (FAILED(hr)) {  
      printf("Failed to get ICommandText interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Create table with image column and index  
   hr = CreateTable(pICommandText);  
   if (FAILED(hr)) {  
      printf("Failed to create table.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Set the DBPROPSET structure.  It is used to pass an array   
   // of DBPROP structures to SetProperties().  
   rgPropSets[0].guidPropertySet = DBPROPSET_ROWSET;  
   rgPropSets[0].cProperties = cProperties;  
   rgPropSets[0].rgProperties = rgProperties;  
  
   // Now set properties in the property group (DBPROPSET_ROWSET)  
   rgPropSets[0].rgProperties[0].dwPropertyID = DBPROP_UPDATABILITY;  
   rgPropSets[0].rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;  
   rgPropSets[0].rgProperties[0].dwStatus = DBPROPSTATUS_OK;  
   rgPropSets[0].rgProperties[0].colid = DB_NULLID;  
   rgPropSets[0].rgProperties[0].vValue.vt = VT_I4;  
   V_I4(&rgPropSets[0].rgProperties[0].vValue) = DBPROPVAL_UP_CHANGE;  
  
   // Set the rowset properties  
   hr = pICommandText->QueryInterface(IID_ICommandProperties,  
      (void **)&pICommandProperties);  
  
   if (FAILED(hr)) {  
      printf("Failed to get ICommandProperties to set rowset properties.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandProperties->SetProperties(cPropSets, rgPropSets);  
  
   if (FAILED(hr)) {  
      printf("Execute failed to set rowset properties.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Execute a command (SELECT * FROM TestISeqStream)  
   hr = pICommandText->SetCommandText(DBGUID_DBSQL, L"SELECT * FROM TestISeqStream");  
  
   if (FAILED(hr)) {  
      printf("Failed to set command text SELECT * FROM.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandText->Execute(NULL,   
      IID_IRowsetChange,   
      NULL,   
      NULL,  
      (IUnknown**)&pIRowsetChange);  
  
   if (FAILED(hr)) {  
      printf("Failed to execute the command SELECT * FROM.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Fill the DBBINDINGS array.  
   rgBindings[0].iOrdinal = 2;   // ordinal position  
   rgBindings[0].obValue = offsetof(BLOBDATA, pISeqStream);  
   rgBindings[0].obLength = offsetof(BLOBDATA, dwLength);  
   rgBindings[0].obStatus = offsetof(BLOBDATA, dwStatus);  
   rgBindings[0].pTypeInfo = NULL;  
   rgBindings[0].pObject = &ObjectStruct;  
   rgBindings[0].pBindExt = NULL;  
   rgBindings[0].dwPart =  DBPART_VALUE | DBPART_STATUS | DBPART_LENGTH;  
   rgBindings[0].dwMemOwner = DBMEMOWNER_CLIENTOWNED;  
   rgBindings[0].eParamIO = DBPARAMIO_NOTPARAM;  
   rgBindings[0].cbMaxLen = 0;   
   rgBindings[0].dwFlags = 0;  
   rgBindings[0].wType = DBTYPE_IUNKNOWN;  
   rgBindings[0].bPrecision = 0;  
   rgBindings[0].bScale = 0;  
  
   // Create an accessor using the binding information.  
   hr = pIRowsetChange->QueryInterface(IID_IAccessor, (void**)&pIAccessor);  
   if (FAILED(hr)) {  
      printf("Failed to get IAccessor interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIAccessor->CreateAccessor(DBACCESSOR_ROWDATA,  
      cBindings,  
      rgBindings,   
      sizeof(BLOBDATA),  
      &hAccessor,  
      rgBindStatus);  
  
   if (FAILED(hr)) {  
      printf("Failed to create an accessor.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // get the first row.  
   hr = pIRowsetChange->QueryInterface(IID_IRowset, (void **)&pIRowset);  
   if (FAILED(hr)) {  
      printf("Failed to get IRowset interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIRowset->GetNextRows(NULL, 0, 1, &cRowsObtained, &rghRows);  
   hr = pIRowset->GetData(rghRows[0], hAccessor, &BLOBGetData);  
  
   // Verify the retrieved data, only if data is not null.  
   if (BLOBGetData.dwStatus == DBSTATUS_S_ISNULL) {  
      // Process null data  
      printf("Provider returned a null value.\n");  
   }   
   else if(BLOBGetData.dwStatus == DBSTATUS_S_OK) {  
      // Provider returned a nonNULL value  
      BLOBGetData.pISeqStream->Read( pBuffer, cBytes, &cBytesRead);  
  
      if (memcmp(pBuffer, pReadData, cBytes) != 0) {  
         // cleanup   
      }  
  
      SAFE_RELEASE(BLOBGetData.pISeqStream);  
   }  
  
   // Set up data for SetData.  
   pMySeqStream = new CSeqStream();  
  
   // Put data into ISequentialStream object for the provider to write.  
   pMySeqStream->Write(pWriteData, cBytes, NULL);  
  
   BLOBSetData.pISeqStream = (ISequentialStream*)pMySeqStream;  
   BLOBSetData.dwStatus = DBSTATUS_S_OK;  
   BLOBSetData.dwLength = pMySeqStream->Length();  
  
   // Set the data.  
   hr = pIRowsetChange->SetData(rghRows[0], hAccessor, &BLOBSetData);  
   if (FAILED(hr))     {  
      printf("Failed to set data.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIAccessor->ReleaseAccessor(hAccessor, NULL);  
   if (FAILED(hr)) {  
      printf("Failed to release accessor.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIRowset->ReleaseRows(cRowsObtained, rghRows, NULL, NULL, NULL);  
  
   if (FAILED(hr)) {  
      printf("Failed to release rows.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
Exit:  
   // Release all allocated memory and release interface pointers.  
   CoUninitialize();  
}  
  
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown) {  
   HRESULT hr = S_OK;  
  
   // Local interface pointers, until a connection is made.  
   IDBInitialize* pIDBInitialize = NULL;  
   IDBProperties*  pIDBProperties = NULL;  
   IDBCreateSession* pIDBCreateSession = NULL;  
   IDBCreateCommand* pIDBCreateCommand = NULL;  
  
   const ULONG cPropSets = 1;  
   DBPROPSET rgPropSets[cPropSets];  
  
   const ULONG cProperties = 4;  
   DBPROP rgProperties[cProperties];  
  
   // Initialize property values needed to establish connection.  
   for ( ULONG i = 0 ; i < 4 ; i++ )  
      VariantInit(&rgProperties[i].vValue);  
  
   // Server name.  
   rgProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;  
   rgProperties[0].vValue.vt = VT_BSTR;  
  
   rgProperties[0].vValue.bstrVal = SysAllocString(L"(local)");  
   rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;  
   rgProperties[0].colid = DB_NULLID;  
  
   // Database.  
   rgProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;  
   rgProperties[1].vValue.vt = VT_BSTR;  
   rgProperties[1].vValue.bstrVal = SysAllocString(L"AdventureWorks");  
   rgProperties[1].dwOptions = DBPROPOPTIONS_REQUIRED;  
   rgProperties[1].colid = DB_NULLID;  
  
   rgProperties[2].dwPropertyID = DBPROP_AUTH_INTEGRATED;  
   rgProperties[2].vValue.vt = VT_BSTR;  
   rgProperties[2].vValue.bstrVal = SysAllocString(L"SSPI");  
   rgProperties[2].dwOptions = DBPROPOPTIONS_REQUIRED;  
   rgProperties[2].colid = DB_NULLID;  
  
   // Properties are now set.  Next, construct DBPROPSET structure (rgInitPropSet) used to pass an   
   // array of DBPROP structures (InitProperties) to the SetProperties method.  
   rgPropSets[0].guidPropertySet = DBPROPSET_DBINIT;  
   rgPropSets[0].cProperties = cProperties;  
   rgPropSets[0].rgProperties = rgProperties;  
  
   // Get the IDBInitialize interface.  
   hr = CoCreateInstance(CLSID_SQLNCLI11,   
      NULL,   
      CLSCTX_INPROC_SERVER,  
      IID_IDBInitialize,   
      (void**)&pIDBInitialize);  
  
   if (FAILED(hr)) {  
      printf("Failed to get IDBInitialize interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Set initialization properties.  
   hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void **)&pIDBProperties);  
   if (FAILED(hr)) {  
      printf("Failed to get IDBProperties interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIDBProperties->SetProperties(cPropSets, rgPropSets);  
   if (FAILED(hr)) {  
      printf("Failed to set properties for DBPROPSET_DBINIT.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIDBInitialize->Initialize();  
   if (FAILED(hr)) {  
      printf("Failed to initialize.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Create a session object.  
   hr = pIDBInitialize->QueryInterface( IID_IDBCreateSession,  
                                        (void **)&pIDBCreateSession);  
  
   if (FAILED(hr)) {  
      printf("Failed to get pIDBCreateSession interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIDBCreateSession->CreateSession( NULL, IID_IDBCreateCommand, (IUnknown**)&pIDBCreateCommand);  
  
   if (FAILED(hr)) {  
      printf("Failed to create session object.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Get CommandText object  
   hr = pIDBCreateCommand->CreateCommand( NULL, riid, (IUnknown**)ppIUnknown);  
  
   if (FAILED(hr)) {  
      printf("Failed to create CommandText object.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   return hr;  
  
Exit:  
   // Free up all allocated memory and release interface pointers.  
   return hr;  
}  
  
HRESULT CreateTable(ICommandText* pICommandText) {  
   HRESULT hr = S_OK;  
  
   // drop the table "TestISeqStream" if the table exists.  
   hr = pICommandText->SetCommandText( DBGUID_DBSQL, L"if object_id('TestISeqStream') is not null drop table TestISeqStream");  
   if (FAILED(hr)) {  
      printf("Failed to set command text DROP TABLE.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);  
   if (FAILED(hr)) {  
      printf("Failed to drop the table.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Create a new table.  
   hr = pICommandText->SetCommandText(DBGUID_DBSQL,   
      L"CREATE TABLE TestISeqStream (col1 int,col2 image)");  
  
   if (FAILED(hr)) {  
      printf("Failed to set command text CREATE TABLE.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);  
   if (FAILED(hr)) {  
      printf("Failed to create table.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Insert one row into table.  
   hr = pICommandText->SetCommandText(DBGUID_DBSQL,  
      L"INSERT INTO TestISeqStream(col1,col2) VALUES (1,0xAAAAAAAAAAAAAAAAA)");  
   if (FAILED(hr)) {  
      printf("Failed to set command text INSERT INTO.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);  
  
   if (FAILED(hr)) {  
      printf("Failed to insert record in the table.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
Exit:  
   // Release all allocated memory and release interface pointers.  
   return hr;  
}

通过

设置大型数据（OLE DB）

过程

设置 BLOB 数据

示例：

DESCRIPTION

代码

其他资源