Windows客户端开发--WMI技术介绍

时光荏苒，六道轮回。
2004年，初中，欧锦赛，希腊神话，17岁的C罗哭成了泪人！
2016年，工作，欧洲杯，能否再让C罗哭成泪人？

想要获得计算机硬件的详细信息，我们可以使用WMI。

今天就作为开篇，谈一谈什么是WMI？
Windows Management Instrumentation (WMI) is a scalable system management infrastructure that uses a single, consistent, standards-based, extensible, object-oriented interface. WMI provides you with a standard way to interact with system management information and the underlying WMI APIs. WMI is used primarily by system management application developers and administrators to access and manipulate system management information.

The purpose of WMI is to provide a standardized means for managing your computer system, be it a local computer or all the computers in an enterprise. In its simplest terms, management is little more than collecting data about the state of a managed object on the computer system and altering the state of the managed object by changing the data stored about the object. A managed object can be a hardware entity, such as a memory array, port, or disk drive. It can also be a software entity, such as a service, user account, or page file.

WMI can manage the many components of a computer system. In managing a hard disk, you can use WMI to monitor the amount of free space remaining on the disk. You could also use WMI to remotely alter the state of the drive by deleting files, changing file security, or partitioning or formatting the drive.

WMI is not only a powerful tool to collect system information, it is also very easy to use. Existing scripting WMI interface makes it possible to be used for system administrators and web-designers as well as for skilled programmers.

WMI的全称是Windows Management Instrumentation，即Windows管理工具。它是Windows操作系统中管理数据和操作的基础模块。我们可以通过WMI脚本或者应用程序去管理本地或者远程计算机上的资源。对于VC和汇编程序员，想获取诸如CPU序列号和硬盘序列号等信息是非常容易的。但是对于VB以及其他一些脚本语言，想尝试获取系统中一些硬件信息可能就没那么容易了。微软为了能达到一种通用性目的（遵守某些行业标准），设计了WMI。它提供了一个通过操作系统、网络和企业环境去管理本地或远程计算机的统一接口集。应用程序和脚本语言使用这套接口集去完成任务，而不是直接通过Windows API。可能有人要问，为什么不让设计的脚本直接在底层使用Windows API，而非要弄个新的技术呢？原因是在目前Windows API中，有些是不支持远程调用或者脚本调用的。这样通过统一模型的WMI，像VB和脚本语言就可以去访问部分系统信息了。但是并不是所有脚本语言都可以使用WMI技术：它要支持ActiveX技术。

先上一个官方的例子：

#define _WIN32_DCOM
#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>

#pragma comment(lib, "wbemuuid.lib")

int main(int argc, char **argv)
{
    HRESULT hres;

    // Step 1: --------------------------------------------------
    // Initialize COM. ------------------------------------------

    hres =  CoInitializeEx(0, COINIT_MULTITHREADED); 
    if (FAILED(hres))
    {
        cout << "Failed to initialize COM library. Error code = 0x" 
            << hex << hres << endl;
        return 1;                  // Program has failed.
    }

    // Step 2: --------------------------------------------------
    // Set general COM security levels --------------------------

    hres =  CoInitializeSecurity(
        NULL, 
        -1,                          // COM authentication
        NULL,                        // Authentication services
        NULL,                        // Reserved
        RPC_C_AUTHN_LEVEL_DEFAULT,   // Default authentication 
        RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation 
        NULL,                        // Authentication info
        EOAC_NONE,                   // Additional capabilities 
        NULL                         // Reserved
        );


    if (FAILED(hres))
    {
        cout << "Failed to initialize security. Error code = 0x" 
            << hex << hres << endl;
        CoUninitialize();
        return 1;                    // Program has failed.
    }

    // Step 3: ---------------------------------------------------
    // Obtain the initial locator to WMI -------------------------

    IWbemLocator *pLoc = NULL;

    hres = CoCreateInstance(
        CLSID_WbemLocator,             
        0, 
        CLSCTX_INPROC_SERVER, 
        IID_IWbemLocator, (LPVOID *) &pLoc);

    if (FAILED(hres))
    {
        cout << "Failed to create IWbemLocator object."
            << " Err code = 0x"
            << hex << hres << endl;
        CoUninitialize();
        return 1;                 // Program has failed.
    }

    // Step 4: -----------------------------------------------------
    // Connect to WMI through the IWbemLocator::ConnectServer method

    IWbemServices *pSvc = NULL;

    // Connect to the root\cimv2 namespace with
    // the current user and obtain pointer pSvc
    // to make IWbemServices calls.
    hres = pLoc->ConnectServer(
         _bstr_t(L"ROOT\\CIMV2"), // Object path of WMI namespace
         NULL,                    // User name. NULL = current user
         NULL,                    // User password. NULL = current
         0,                       // Locale. NULL indicates current
         NULL,                    // Security flags.
         0,                       // Authority (for example, Kerberos)
         0,                       // Context object 
         &pSvc                    // pointer to IWbemServices proxy
         );

    if (FAILED(hres))
    {
        cout << "Could not connect. Error code = 0x" 
             << hex << hres << endl;
        pLoc->Release();     
        CoUninitialize();
        return 1;                // Program has failed.
    }

    cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;


    // Step 5: --------------------------------------------------
    // Set security levels on the proxy -------------------------

    hres = CoSetProxyBlanket(
       pSvc,                        // Indicates the proxy to set
       RPC_C_AUTHN_WINNT,           // RPC_C_AUTHN_xxx
       RPC_C_AUTHZ_NONE,            // RPC_C_AUTHZ_xxx
       NULL,                        // Server principal name 
       RPC_C_AUTHN_LEVEL_CALL,      // RPC_C_AUTHN_LEVEL_xxx 
       RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
       NULL,                        // client identity
       EOAC_NONE                    // proxy capabilities 
    );

    if (FAILED(hres))
    {
        cout << "Could not set proxy blanket. Error code = 0x" 
            << hex << hres << endl;
        pSvc->Release();
        pLoc->Release();     
        CoUninitialize();
        return 1;               // Program has failed.
    }

    // Step 6: --------------------------------------------------
    // Use the IWbemServices pointer to make requests of WMI ----

    // For example, get the name of the operating system
    IEnumWbemClassObject* pEnumerator = NULL;
    hres = pSvc->ExecQuery(
        bstr_t("WQL"), 
        bstr_t("SELECT * FROM Win32_OperatingSystem"),
        WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, 
        NULL,
        &pEnumerator);

    if (FAILED(hres))
    {
        cout << "Query for operating system name failed."
            << " Error code = 0x" 
            << hex << hres << endl;
        pSvc->Release();
        pLoc->Release();
        CoUninitialize();
        return 1;               // Program has failed.
    }

    // Step 7: -------------------------------------------------
    // Get the data from the query in step 6 -------------------

    IWbemClassObject *pclsObj = NULL;
    ULONG uReturn = 0;

    while (pEnumerator)
    {
        HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1, 
            &pclsObj, &uReturn);

        if(0 == uReturn)
        {
            break;
        }

        VARIANT vtProp;

        // Get the value of the Name property
        hr = pclsObj->Get(L"Name", 0, &vtProp, 0, 0);
        wcout << " OS Name : " << vtProp.bstrVal << endl;
        VariantClear(&vtProp);

        pclsObj->Release();
    }

    // Cleanup
    // ========

    pSvc->Release();
    pLoc->Release();
    pEnumerator->Release();
    CoUninitialize();

    return 0;   // Program successfully completed.

}

步骤：
初始化COM库
设置进程COM安全信息
创建进程内COM服务器
连接WMI命名空间
设置WMI连接的安全等级
发起WMI请求
清理

接下来的操作就是换汤不换药。

这里有个忠告，免费的：
把上面的例子代码粘贴到自己的工程中时，一定要养成review的习惯，去掉不必要的注释，不必要的空行。

上面的代码中用到了很多api，这里不再一一赘述，请参阅msdn官方文档。

这里仅仅是个开始，接下来要发生的事儿：

1 win32控制台程序中查看计算机显卡的详细信息

2 为何在GUI程序中，使用win32控制台程序同样的方法，我们无法获得正确的信息呢？

3 qt中使用WMI中遇到了哪些坑。

coming soon~~~~~