Como obter o último conjunto de cabeçalhos HTTP recebidos para cada arquivo em um trabalho de download do BITS
Este exemplo mostra como usar o método GetProperty da nova interface IBackgroundCopyJob5 para obter os últimos cabeçalhos HTTP de conjunto recebidos para cada arquivo em um trabalho de download do BITS (Serviço de Transferência Inteligente em Segundo Plano). As informações no cabeçalho HTTP podem ser usadas, por exemplo, para determinar o tipo de arquivo ou quando ele foi alterado pela última vez no servidor. Antes do Windows 8 e do Windows Server 2012, o BITS não fornecia um meio pelo qual o aplicativo pudesse recuperar e inspecionar os cabeçalhos de resposta HTTP de um download concluído. Este exemplo mostra como usar a API do BITS para criar um trabalho do BITS com várias URLs para download, listar as URLs em um trabalho e recuperar os cabeçalhos de resposta HTTP para cada URL.
O que você precisa saber
Tecnologias
Pré-requisitos
- Microsoft Visual Studio
Instruções
Etapa 1: Incluir os arquivos de cabeçalho BITS necessários
Insira as seguintes diretivas de cabeçalho na parte superior do arquivo de origem.
#include <bits.h>
Etapa 2: inicializar o COM e instanciar uma interface de objeto do Gerenciador de cópias em segundo plano do BITS
Antes de instanciar a interface IBackgroundCopyManager (usada para criar um trabalho do BITS), você deve inicializar o COM e definir o modelo de threading COM desejado.
// Initialize COM and specify the appropriate COM threading model for your application.
IBackgroundCopyManager* pManager;
HRESULT hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
if (SUCCEEDED(hr))
{
hr = CoCreateInstance(__uuidof(BackgroundCopyManager),
NULL,
CLSCTX_LOCAL_SERVER,
__uuidof(IBackgroundCopyManager),
(void**) &pManager);
}
Etapa 3: Criar o trabalho do BITS
Somente o usuário que cria o trabalho ou um usuário com privilégios de administrador pode adicionar arquivos ao trabalho e alterar as propriedades do trabalho.
GUID guidJob;
IBackgroundCopyJob* pBackgroundCopyJob;
hr = pManager->CreateJob(L"TransferPolicy",
BG_JOB_TYPE_DOWNLOAD,
&guidJob,
(IBackgroundCopyJob **)&pBackgroundCopyJob);
Etapa 4: Adicionar os arquivos ao trabalho do BITS
O exemplo a seguir baixa documentos disponíveis publicamente do Centro de Download da Microsoft. Você precisará alterar esses valores para seu ambiente específico.
// Array that contains multiple DOWNLOAD_FILE data structures that represent the
// files that will be added to the download job.
DOWNLOAD_FILE FileList[] =
{
{
L"https://download.microsoft.com/download/0/2/8/02809141-3329-4412-8AC4-AA41B406055C/WinRT81-HttpClient-BT-Socket-Poster.pdf",
L"c:\\temp\\data\\WinRT81-HttpClient-BT-Socket-Poster.pdf"
},
{
L"https://download.microsoft.com/download/6/6/2/662DD05E-BAD7-46EF-9431-135F9BAE6332/9781509302963_Microsoft%20Azure%20Essentials%20Fundamentals%20of%20Azure%202nd%20ed%20pdf.pdf",
L"c:\\temp\\data\\Fundamentals of Azure.pdf"
},
{
L"https://aka.ms/WinServ16/StndPDF",
L"c:\\temp\\data\\IntroducingWindowsServer2016.pdf"
}
};
...
// Add the files to the job.
for (int i=0; i < ARRAY_LENGTH(FileList); ++i)
{
hr = Job->AddFile(FileList[i].RemoteFile,
FileList[i].LocalFile);
...
}
Etapa 5: Iniciar o trabalho do BITS
Depois de configurar o trabalho do BITS, chame a função Retomar da interface IBackgroundCopyJob para iniciar ou continuar o download.
// Start the BITS job.
hr = pBackgroundJob->Resume();
Etapa 6: monitorar e exibir o progresso do trabalho do BITS
A MonitorJobProgress função auxiliar usa um objeto IBackgroundCopyJob como seu único parâmetro e sonda o trabalho para um status a cada 500 milissegundos. Essa função não retorna até que o trabalho seja concluído ou cancelado.
HRESULT MonitorJobProgress(__in IBackgroundCopyJob* Job)
{
HRESULT hr;
LPWSTR JobName;
BG_JOB_STATE State;
int PreviousState = -1;
bool Exit = false;
int ProgressCounter = 0;
hr = Job->GetDisplayName(&JobName);
printf("Progress report for download job '%ws'.\n", JobName);
CoTaskMemFree(JobName);
// Display the download progress.
while (!Exit)
{
hr = Job->GetState(&State);
if (State != PreviousState)
{
switch(State)
{
case BG_JOB_STATE_QUEUED:
printf("Job is in the queue and waiting to run.\n");
break;
case BG_JOB_STATE_CONNECTING:
printf("BITS is trying to connect to the remote server.\n");
break;
case BG_JOB_STATE_TRANSFERRING:
printf("BITS has started downloading data.\n");
DisplayProgress( Job );
break;
case BG_JOB_STATE_ERROR:
wprintf(L"ERROR: BITS has encountered a non-recoverable error.\n");
DisplayError(Job);
wprintf(L" Exiting job.\n");
Exit = true;
break;
case BG_JOB_STATE_TRANSIENT_ERROR:
wprintf(L"ERROR: BITS has encountered a recoverable error.\n");
DisplayError(Job);
wprintf(L" Continuing to retry.\n");
break;
case BG_JOB_STATE_TRANSFERRED:
DisplayProgress(Job);
printf("The job has been successfully completed.\n");
printf("Finalizing local files.\n");
Job->Complete();
break;
case BG_JOB_STATE_ACKNOWLEDGED:
printf("Finalization complete.\n");
Exit = true;
break;
case BG_JOB_STATE_CANCELLED:
printf("WARNING: The job has been cancelled.\n");
Exit = true;
break;
default:
printf("WARNING: Unknown BITS state %d.\n", State);
Exit = true;
}
PreviousState = State;
}
else if (State == BG_JOB_STATE_TRANSFERRING)
{
// Display job progress every 2 seconds.
if (++ProgressCounter % TWO_SECOND_LOOP == 0)
{
DisplayProgress( Job );
}
}
Sleep(HALF_SECOND_AS_MILLISECONDS);
}
printf("\n");
return hr;
}
// Display the current progress of the job in terms of the amount of data
// and number of files transferred.
VOID DisplayProgress(__in IBackgroundCopyJob *Job)
{
HRESULT hr;
BG_JOB_PROGRESS Progress;
hr = Job->GetProgress(&Progress);
if (SUCCEEDED(hr))
{
printf("%llu of %llu bytes transferred (%lu of %lu files).\n",
Progress.BytesTransferred, Progress.BytesTotal,
Progress.FilesTransferred, Progress.FilesTotal);
}
}
Etapa 7: Exibir os cabeçalhos de arquivo baixados
A DisplayFileHeaders função auxiliar enumera os trabalhos definidos para um objeto IBackgroundCopyJob .
// For each file in the job, obtain and display the HTTP header received server.
HRESULT DisplayFileHeaders(__in IBackgroundCopyJob *Job)
{
HRESULT hr;
IEnumBackgroundCopyFiles *FileEnumerator;
hr = Job->EnumFiles(&FileEnumerator);
if (SUCCEEDED(hr))
{
ULONG Count;
hr = FileEnumerator->GetCount(&Count);
if (SUCCEEDED(hr))
{
for (ULONG i=0; i < Count; ++i)
{
IBackgroundCopyFile *TempFile;
hr = FileEnumerator->Next(1, &TempFile, NULL);
if (SUCCEEDED(hr))
{
IBackgroundCopyFile5 *File;
hr = TempFile->QueryInterface(__uuidof( IBackgroundCopyFile5 ), (void **) &File);
if (SUCCEEDED(hr))
{
LPWSTR RemoteFileName;
hr = File->GetRemoteName(&RemoteFileName);
if (SUCCEEDED(hr))
{
printf("HTTP headers for remote file '%ws'\n", RemoteFileName );
CoTaskMemFree( RemoteFileName );
RemoteFileName = NULL;
}
BITS_FILE_PROPERTY_VALUE Value;
hr = File->GetProperty(BITS_FILE_PROPERTY_ID_HTTP_RESPONSE_HEADERS, &Value);
if (SUCCEEDED(hr) && Value.String)
{
printf("Headers: %ws\n", Headers );
CoTaskMemFree(Value.String);
Value.String = NULL;
}
File->Release();
File = NULL;
}
TempFile->Release();
TempFile = NULL;
}
}
}
FileEnumerator->Release();
FileEnumerator = NULL;
}
return S_OK;
}
Exemplo
O exemplo de código a seguir é um aplicativo de console totalmente funcional que mostra como usar a API do BITS para criar um trabalho do BITS com várias URLs para download, listar as URLs em um trabalho e recuperar os cabeçalhos de resposta HTTP para cada URL.
//*********************************************************
//
// Copyright (c) Microsoft. All rights reserved.
// This code is licensed under the Microsoft Public License.
// THIS CODE IS PROVIDED *AS IS* WITHOUT WARRANTY OF
// ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING ANY
// IMPLIED WARRANTIES OF FITNESS FOR A PARTICULAR
// PURPOSE, MERCHANTABILITY, OR NON-INFRINGEMENT.
//
//*********************************************************
#define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers
#include <windows.h>
#include <bits.h>
#include <stdio.h> // needed for wprintf
#include <strsafe.h>
#define ARRAY_LENGTH(x) (sizeof(x) / sizeof( *(x) ))
// Definition of constants.
static const unsigned int HALF_SECOND_AS_MILLISECONDS = 500;
static const unsigned int TWO_SECOND_LOOP = 2000 / HALF_SECOND_AS_MILLISECONDS;
// Simple data structure that contains the remote and local names for a file.
typedef struct
{
LPCWSTR RemoteFile;
LPCWSTR LocalFile;
} DOWNLOAD_FILE;
// Array that contains sample DOWNLOAD_FILE data structures that represent the files
// that will be added to the download job.
DOWNLOAD_FILE FileList[] =
{
{
L"https://download.microsoft.com/download/0/2/8/02809141-3329-4412-8AC4-AA41B406055C/WinRT81-HttpClient-BT-Socket-Poster.pdf",
L"c:\\temp\\data\\WinRT81-HttpClient-BT-Socket-Poster.pdf"
},
{
L"https://download.microsoft.com/download/6/6/2/662DD05E-BAD7-46EF-9431-135F9BAE6332/9781509302963_Microsoft%20Azure%20Essentials%20Fundamentals%20of%20Azure%202nd%20ed%20pdf.pdf",
L"c:\\temp\\data\\Fundamentals of Azure.pdf"
},
{
L"https://aka.ms/WinServ16/StndPDF",
L"c:\\temp\\data\\IntroducingWindowsServer2016.pdf"
}
};
// Forward declaration of functions.
HRESULT GetBackgroundCopyManager(__out IBackgroundCopyManager **Manager);
HRESULT CreateDownloadJob(__in LPCWSTR Name, __in IBackgroundCopyManager *Manager, __out IBackgroundCopyJob **Job);
HRESULT MonitorJobProgress(__in IBackgroundCopyJob *Job);
HRESULT DisplayFileHeaders(__in IBackgroundCopyJob *Job);
VOID DisplayProgress(__in IBackgroundCopyJob *Job);
VOID DisplayHeaders(__in LPWSTR Headers);
VOID DisplayError(__in IBackgroundCopyJob *Job);
// Main program entry point.
int wmain(int argc, wchar_t* argv[])
{
HRESULT hr;
IBackgroundCopyManager *Manager;
// Get the BITS Background Copy Manager.
hr = GetBackgroundCopyManager(&Manager);
if (SUCCEEDED(hr))
{
IBackgroundCopyJob *Job;
// Create a new download job.
hr = CreateDownloadJob(L"MyJob", Manager, &Job);
if (SUCCEEDED(hr))
{
// Add files to the job.
for (int i = 0; i < ARRAY_LENGTH(FileList); ++i)
{
hr = Job->AddFile(FileList[i].RemoteFile, FileList[i].LocalFile);
if (FAILED(hr))
{
wprintf(L"Error: Unable to add remote file '%ws' to the download job (error %08X).\n",
FileList[i].RemoteFile,
hr);
}
else
{
wprintf(L"Downloading remote file '%ws' to local file '%ws'\n",
FileList[i].RemoteFile, FileList[i].LocalFile);
}
}
// Start the job and display its progress.
hr = Job->Resume();
if (FAILED(hr))
{
wprintf(L"ERROR: Unable to start the BITS download job (error code %08X).\n", hr);
}
else
{
MonitorJobProgress(Job);
}
// Release the BITS IBackgroundCopyJob interface.
Job->Release();
Job = NULL;
}
// Release the IBackgroundCopyManager interface.
Manager->Release();
Manager = NULL;
}
return 0;
}
/**
* Gets a pointer to the BITS Background Copy Manager.
*
* If successful, this function returns a success code and sets the
* referenced IBackgroundCopyFileManager interface pointer to a
* reference counted instance of the Background Copy Manager interface.
*/
HRESULT GetBackgroundCopyManager(__out IBackgroundCopyManager **Manager)
{
HRESULT hr;
//Specify the appropriate COM threading model for your application.
hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
if (SUCCEEDED(hr))
{
hr = CoCreateInstance(__uuidof(BackgroundCopyManager),
NULL,
CLSCTX_LOCAL_SERVER,
__uuidof(IBackgroundCopyManager),
(void**)Manager);
}
else
{
wprintf(L"ERROR: Unable to initialize COM (error code %08X).\n", hr);
}
return hr;
}
/**
* Creates a new download job with the specified name.
*/
HRESULT CreateDownloadJob(__in LPCWSTR Name, __in IBackgroundCopyManager *Manager, __out IBackgroundCopyJob **Job)
{
GUID guid;
return Manager->CreateJob(Name, BG_JOB_TYPE_DOWNLOAD, &guid, Job);
}
/**
* Monitors and displays the progress of the download job.
*
* A new status message is output whenever the job's status changes or,
* when transferring data, every 2 seconds displays how much data
* has been transferred.
*/
HRESULT MonitorJobProgress(__in IBackgroundCopyJob *Job)
{
HRESULT hr;
LPWSTR JobName;
BG_JOB_STATE State;
int PreviousState = -1;
bool Exit = false;
int ProgressCounter = 0;
hr = Job->GetDisplayName(&JobName);
wprintf(L"Progress report for download job '%ws'.\n", JobName);
CoTaskMemFree(JobName);
// Display the download progress.
while (!Exit)
{
hr = Job->GetState(&State);
if (State != PreviousState)
{
switch (State)
{
case BG_JOB_STATE_QUEUED:
wprintf(L"Job is in the queue and waiting to run.\n");
break;
case BG_JOB_STATE_CONNECTING:
wprintf(L"BITS is trying to connect to the remote server.\n");
break;
case BG_JOB_STATE_TRANSFERRING:
wprintf(L"BITS has started downloading data.\n");
DisplayProgress(Job);
break;
case BG_JOB_STATE_ERROR:
wprintf(L"ERROR: BITS has encountered a non-recoverable error.\n");
DisplayError(Job);
wprintf(L" Exiting job.\n");
Exit = true;
break;
case BG_JOB_STATE_TRANSIENT_ERROR:
wprintf(L"ERROR: BITS has encountered a recoverable error.\n");
DisplayError(Job);
wprintf(L" Continuing to retry.\n");
break;
case BG_JOB_STATE_TRANSFERRED:
DisplayProgress(Job);
wprintf(L"The job has been successfully completed.\n");
wprintf(L"Finalizing local files.\n");
Job->Complete();
break;
case BG_JOB_STATE_ACKNOWLEDGED:
wprintf(L"Finalization complete.\n");
Exit = true;
break;
case BG_JOB_STATE_CANCELLED:
wprintf(L"WARNING: The job has been cancelled.\n");
Exit = true;
break;
default:
wprintf(L"WARNING: Unknown BITS state %d.\n", State);
Exit = true;
}
PreviousState = State;
}
else if (State == BG_JOB_STATE_TRANSFERRING)
{
// Display job progress every 2 seconds.
if (++ProgressCounter % TWO_SECOND_LOOP == 0)
{
DisplayProgress(Job);
}
}
Sleep(HALF_SECOND_AS_MILLISECONDS);
}
wprintf(L"\n");
if (SUCCEEDED(hr))
{
hr = DisplayFileHeaders(Job);
}
return hr;
}
/**
* For each file in the job, obtains the (final) HTTP headers received from the
* remote server that hosts the files and then displays the HTTP headers.
*/
HRESULT DisplayFileHeaders(__in IBackgroundCopyJob *Job)
{
HRESULT hr;
IEnumBackgroundCopyFiles *FileEnumerator;
wprintf(L"Individual file information.\n");
hr = Job->EnumFiles(&FileEnumerator);
if (FAILED(hr))
{
wprintf(L"WARNING: Unable to obtain an IEnumBackgroundCopyFiles interface.\n");
wprintf(L" No further information can be provided about the files in the job.\n");
}
else
{
ULONG Count;
hr = FileEnumerator->GetCount(&Count);
if (FAILED(hr))
{
wprintf(L"WARNING: Unable to obtain a count of the number of files in the job.\n");
wprintf(L" No further information can be provided about the files in the job.\n");
}
else
{
for (ULONG i = 0; i < Count; ++i)
{
IBackgroundCopyFile *TempFile;
hr = FileEnumerator->Next(1, &TempFile, NULL);
if (FAILED(hr))
{
wprintf(L"WARNING: Unable to obtain an IBackgroundCopyFile interface for the next file in the job.\n");
wprintf(L" No further information can be provided about this file.\n");
}
else
{
IBackgroundCopyFile5 *File;
hr = TempFile->QueryInterface(__uuidof(IBackgroundCopyFile5), (void **)&File);
if (FAILED(hr))
{
wprintf(L"WARNING: Unable to obtain an IBackgroundCopyFile5 interface for the file.\n");
wprintf(L" No further information can be provided about this file.\n");
}
else
{
LPWSTR RemoteFileName;
hr = File->GetRemoteName(&RemoteFileName);
if (FAILED(hr))
{
wprintf(L"WARNING: Unable to obtain the remote file name for this file.\n");
}
else
{
wprintf(L"HTTP headers for remote file '%ws'\n", RemoteFileName);
CoTaskMemFree(RemoteFileName);
RemoteFileName = NULL;
}
BITS_FILE_PROPERTY_VALUE Value;
hr = File->GetProperty(BITS_FILE_PROPERTY_ID_HTTP_RESPONSE_HEADERS, &Value);
if (FAILED(hr))
{
wprintf(L"WARNING: Unable to obtain the HTTP headers for this file.\n");
}
else
{
if (Value.String)
{
DisplayHeaders(Value.String);
CoTaskMemFree(Value.String);
Value.String = NULL;
}
}
File->Release();
File = NULL;
}
TempFile->Release();
TempFile = NULL;
}
}
}
FileEnumerator->Release();
FileEnumerator = NULL;
}
return S_OK;
}
/**
* Displays the current progress of the job in terms of the amount of data
* and number of files transferred.
*/
VOID DisplayProgress(__in IBackgroundCopyJob *Job)
{
HRESULT hr;
BG_JOB_PROGRESS Progress;
hr = Job->GetProgress(&Progress);
if (SUCCEEDED(hr))
{
wprintf(L"%llu of %llu bytes transferred (%lu of %lu files).\n",
Progress.BytesTransferred, Progress.BytesTotal,
Progress.FilesTransferred, Progress.FilesTotal);
}
else
{
wprintf(L"ERROR: Unable to get job progress (error code %08X).\n", hr);
}
}
/**
* Parses the provided string that contains HTTP headers,
* splits them apart and displays them to the user.
*/
VOID DisplayHeaders(__in LPWSTR Headers)
{
wprintf(L"Headers: %ws\n", Headers);
}
VOID DisplayError(__in IBackgroundCopyJob *Job)
{
HRESULT hr;
IBackgroundCopyError *Error;
LPWSTR ErrorDescription;
hr = Job->GetError(&Error);
if (FAILED(hr))
{
wprintf(L"WARNING: Unable to get job error information (code %08X)\n", hr);
}
else
{
BG_ERROR_CONTEXT ErrorContext;
HRESULT ErrorResult;
hr = Error->GetError(&ErrorContext, &ErrorResult);
if (FAILED(hr))
{
wprintf(L"WARNING: Unable to get job error code information (code %08X)\n", hr);
}
else
{
hr = Error->GetErrorDescription(LANGIDFROMLCID(GetThreadLocale()), &ErrorDescription);
if (FAILED(hr))
{
wprintf(L"WARNING: Unable to get job error description (code %08X) for %08X\n", hr, ErrorResult);
}
else
{
wprintf(L" Error details: code %08X %ws\n", ErrorResult, ErrorDescription);
CoTaskMemFree(ErrorDescription);
}
}
Error->Release();
}
}
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