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java - 如何访问 WMI 查询的数据（通过 JNA）SAFEARRAY 结果

问题描述

我使用 jna 来运行 WMI 查询。以下代码查询 WMI SELECT Caption,Capabilities from Win32_DiskDrive。Win32_DiskDrive.Capabilities 的类型是 uint16[] 并且 result.getValue 返回一个 SAFEARRAY 实例。

System.out.println("Var Type(3 expected): " + value.getVarType().intValue());

如果我多次启动该过程，则随机返回 0 或 3。

System.out.println("Size (>0 expected): " + (value.getUBound(0) - value.getLBound(0)));

是正确的，但是

Object el = value.getElement(0);

失败。

value.accessData();

返回 null 这也是意外的，所以我不能使用 OaIdlUtil#toPrimitiveArray (Nullpointer)

不幸的是，代码不起作用，我不知道可能出了什么问题。有任何想法吗？

enum Win32_DiskDrive_Values {
        Caption,
        Capabilities
    }

    public static void main(String[] args) throws IOException, InterruptedException {
        try {
            WmiQuery<Win32_DiskDrive_Values> serialNumberQuery = new WmiQuery<Win32_DiskDrive_Values>("Win32_DiskDrive", Win32_DiskDrive_Values.class);
            Ole32.INSTANCE.CoInitializeEx(null, Ole32.COINIT_MULTITHREADED);
            WmiResult<Win32_DiskDrive_Values> result = serialNumberQuery.execute();
            for (int i = 0; i < result.getResultCount(); i++) {
                System.out.println(result.getValue(Win32_DiskDrive_Values.Caption, i));
                SAFEARRAY value = (SAFEARRAY) result.getValue(Win32_DiskDrive_Values.Capabilities, i);
                // According to https://docs.microsoft.com/en-us/windows/desktop/cimwin32prov/win32-diskdrive, the type of Capabilities
                // should be uint16[] which should be Variant.VT_I2 (2-byte integer)
                // however, it is not constant. sometimes it is 0, sometimes Variant.VT_I2 (3);
                System.out.println("Var Type(3 expected): " + value.getVarType().intValue());
                System.out.println("Size (>0 expected): " + (value.getUBound(0) - value.getLBound(0)));
                Object el = value.getElement(0);
                System.out.println("Element 0 (!=null expected): " + el);
                Pointer pointer = value.accessData();
                System.out.println("pointer (!=null expected): " + pointer);
            }
        } catch (Throwable e) {
            e.printStackTrace();
        } finally {
            Ole32.INSTANCE.CoUninitialize();
        }
    }

标签： javawmijna

解决方案

我提交给 JNA 项目的 WMI 代码仅用于处理原始值和字符串，而不是数组。您遇到的问题是 WMI 将指针地址返回到数组（VT_EMPTY = 0 的空数组或 VT_I4 = 3 的 32 位指针）。但是 WMI 结果是在迭代之后释放的，所以不能使用WmiResult来获取对象。

您需要编写自己的代码（使用 JNA 实现作为起点）来获取SAFEARRAY迭代期间的内容。您在 JNA 网站上提出了这个问题，@matthiasblaesing 发布了以下适用于您的用例的片段：

public static void main(String[] args) throws IOException, InterruptedException {
    Ole32.INSTANCE.CoInitializeEx(null, Ole32.COINIT_MULTITHREADED);

    // Connect to the server
    Wbemcli.IWbemServices svc = WbemcliUtil.connectServer("ROOT\\CIMV2");

    // Send query
    try {
        Wbemcli.IEnumWbemClassObject enumerator = svc.ExecQuery("WQL", "SELECT Caption, Capabilities, CapabilityDescriptions FROM Win32_DiskDrive",
                Wbemcli.WBEM_FLAG_FORWARD_ONLY | Wbemcli.WBEM_FLAG_RETURN_IMMEDIATELY, null);

        try {
            IWbemClassObject[] result;
            VARIANT.ByReference pVal = new VARIANT.ByReference();
            IntByReference pType = new IntByReference();
            IntByReference plFlavor = new IntByReference();
            while(true) {
                result = enumerator.Next(0, 1);
                if(result.length == 0) {
                    break;
                }
                COMUtils.checkRC(result[0].Get("Caption", 0, pVal, pType, plFlavor));
                System.out.println("---------" + pVal.getValue() + "-------------");
                OleAuto.INSTANCE.VariantClear(pVal);
                COMUtils.checkRC(result[0].Get("CapabilityDescriptions", 0, pVal, pType, plFlavor));
                SAFEARRAY safeArray = (SAFEARRAY) pVal.getValue();
                for(int i = safeArray.getLBound(0); i<=safeArray.getUBound(0); i++) {
                    System.out.println("\t" + safeArray.getElement(i));
                }
                OleAuto.INSTANCE.VariantClear(pVal);
                COMUtils.checkRC(result[0].Get("Capabilities", 0, pVal, pType, plFlavor));
                safeArray = (SAFEARRAY) pVal.getValue();
                for(int i = safeArray.getLBound(0); i<=safeArray.getUBound(0); i++) {
                    System.out.println("\t" + safeArray.getElement(i));
                }
                OleAuto.INSTANCE.VariantClear(pVal);
                result[0].Release();
            }
        } finally {
            // Cleanup
            enumerator.Release();
        }
    } finally {
        // Cleanup
        svc.Release();
    }

    Ole32.INSTANCE.CoUninitialize();
}

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