Posts Tagged ‘DMTF’

WMI – WBEM – Microsoft Hyper-V from Java – Linux

April 21st, 2010 jmguilla 19 comments

Hyper-V Management API

Hyper-V, take the control from your Java code.

We cannot say that there is a particular API allowing remotely manage Microsoft Hyper-V. Microsoft simply inserted new components related to virtualization to its existing WMI interface. WMI is Microsoft’s WBEM implementation using DCOM as communication layer instead of HTTP like it was planned by the standard. You can easily guess that it is really convenient for use from a Window environment but far more annoying from a Linux operating system. Here is a brief explanation about how to get that to work from a Java/Linux environment!

J-Interop, pure Java-DCOM bridge.

The solution to be able to reach a remote COM object from a Java environment is J-Interop, a pure Java-DCOM bridge. The word “pure” is used to show that there isn’t any tricky things like native Win32 library calls or anything else ( on a Linux platform, it would have been clumsy ). This API is straightforward to use, just connect to the service you want to use and call methods. You can also create new COM object on local/remote computer. Check the quickstart to see how does it work.

WMI to manage Hyper-V

As I said at the beginning, WMI is used to manage Microsoft Hyper-V environment. You can do every thing you want using this interface except actions related to file management. For example, if you play with differencing hard disks, for virtual machine clone creation ( among many possible things… ), you will be able to create files but won’t be able to delete them. To get that done, you will have to connect to default CIMV2 namespace and use CIM_Datafile class. I assume there is many other limitations in the virtualization namespace, but I haven’t found any so far. Below is an example showing how to create a new KVP exchange data item:

$ComputerName = "localhost" $VMManagementService = Get-WmiObject -class "Msvm_VirtualSystemManagementService" -namespace "root\virtualization" -ComputerName $ComputerName
$Vm = Get-WmiObject -Namespace root\virtualization -ComputerName $ComputerName -Query "Select * From Msvm_ComputerSystem Where ElementName='Vista'" $Kvp = Get-WmiObject -Namespace root\virtualization -ComputerName $ComputerName -Query "Associators of {$Vm} Where AssocClass=Msvm_SystemDevice ResultClass=Msvm_KvpExchangeComponent"
$Msvm_KvpExchangeDataItemPath = "\\$ComputerName\root\virtualization:Msvm_KvpExchangeDataItem"
$Msvm_KvpExchangeDateItem = [WmiClass]$Msvm_KvpExchangeDataItemPath).CreateInstance()
$Msvm_KvpExchangeDateItem.Name = "bootstrapURL"
$Msvm_KvpExchangeDateItem.Data = ""
$Msvm_KvpExchangeDateItem.Source = 0
$VMManagementService.AddKvpItems($Vm, $Msvm_KvpExchangeDateItem.PSBase.GetText(1))

Hyper-V’s WMI + J-Interop

Now we put every pieces together to manage Microsoft Hyper-V. Here is an example on how to connect to the Wbem service locator:

JISession session = JISession.createSession("", "user", "password");
JIComServer comServer = new JIComServer(JIProgId.valueOf("WbemScripting.SWbemLocator"), "", session);
IJIComObject wimObject = comServer.createInstance();
IJIDispatch locatorDispatch = (IJIDispatch) JIObjectFactory.narrowObject((IJIComObject) wimObject
Object[] params = new Object[] { new JIString(url), new JIString(namespace),
        JIVariant.OPTIONAL_PARAM(), new Integer(0), JIVariant.OPTIONAL_PARAM() };
JIVariant[] res = locatorDispatch.callMethodA("connectServer", params);
IJIDispatch service = (IJIDispatch) JIObjectFactory.narrowObject(res[0].getObjectAsComObject());

Or here, where we print every Msvm_VirtualSwitch’s path:

import static org.jinterop.dcom.impls.JIObjectFactory.narrowObject;
import java.util.ArrayList;
import java.util.logging.Level;
import org.jinterop.dcom.common.JIException;
import org.jinterop.dcom.common.JISystem;
import org.jinterop.dcom.core.IJIComObject;
import org.jinterop.dcom.core.JIArray;
import org.jinterop.dcom.core.JIComServer;
import org.jinterop.dcom.core.JIProgId;
import org.jinterop.dcom.core.JISession;
import org.jinterop.dcom.core.JIString;
import org.jinterop.dcom.core.JIVariant;
import org.jinterop.dcom.impls.JIObjectFactory;
import org.jinterop.dcom.impls.automation.IJIDispatch;
import org.jinterop.dcom.impls.automation.IJIEnumVariant;
public class PrintVSPath {
        public static String domain = "DOMAIN";
	public static String url = "SERVER_NAME";
	public static String user = "USER";
	public static String pwd = "PASSWORD";
	public static void main(String[] args) throws JIException, SecurityException, IOException{
		JISession session = null;
			//J-Interop settings
			session = JISession.createSession(domain,user,pwd);
			JIComServer comServer = new JIComServer(JIProgId.valueOf("WbemScripting.SWbemLocator"),url,session);
			IJIComObject wimObject = comServer.createInstance();
			IJIDispatch locatorDispatch = (IJIDispatch)JIObjectFactory.narrowObject((IJIComObject)wimObject.queryInterface(IJIDispatch.IID));
			Object[] params = new Object[]{
					new JIString(url),
					new JIString("root\\virtualization"),
					new Integer(0),
			JIVariant[] res = locatorDispatch.callMethodA("connectServer",params);
			IJIDispatch sWbemServices = (IJIDispatch) JIObjectFactory.narrowObject(res[0].getObjectAsComObject().queryInterface(IJIDispatch.IID));
			res = sWbemServices.callMethodA("ExecQuery", new Object[]{
					new JIString("Select * From Msvm_VirtualSwitch"),
					new JIVariant(new Integer(0x10 + 0x20))
			JIVariant[][] resSet = enumToJIVariantArray(res);
			IJIDispatch vsDispatch = (IJIDispatch)JIObjectFactory.narrowObject(resSet[0][0].getObjectAsComObject().queryInterface(IJIDispatch.IID));
			if(session != null)
	public static JIVariant[][] enumToJIVariantArray(JIVariant[] set) throws JIException{
		IJIDispatch toConvertDispatch = (IJIDispatch)narrowObject(set[0].getObjectAsComObject().queryInterface(IJIDispatch.IID));
		JIVariant toConvertVariant = toConvertDispatch.get("_NewEnum");
		IJIComObject toConvertComObject = toConvertVariant.getObjectAsComObject();
		IJIEnumVariant toConvertEnumVariant = (IJIEnumVariant)narrowObject(toConvertComObject.queryInterface(IJIEnumVariant.IID));
		ArrayList<JIVariant[]> res = new ArrayList<JIVariant[]>();
		int i = 0, threshold = 1000000; //to avoid infinite loop, in both msdn and j-interop nothing is said about enumeration
			Object[] values = null;
				values =;
			}catch(JIException e){
			if(values != null){
				JIArray array = (JIArray) values[0];
			if( i >= threshold){
		return res.toArray(new JIVariant[res.size()][]);

DMTF’s CIM and interoperability

April 6th, 2010 jmguilla No comments
Computer administration and Caveats ( how DMTF’s CIM can help )

I had a great exchange with one of co-workers today about interoperability and how Linux OSes are good and far better than Windows OSes. His point of view is that thanks to SSH and the Linux’s shell ( and POSIX ) it is really easy to manage a set of Linux computer. That’s why the Linux community does “many” things for the interoperability sake… Even if I am a Linux fan boy, I can’t join that point of view…

Have you already heard about DMTF? DMTF stands for “Distributed Management Task Force”, presided by Winston Bumpus, who is a core individual @ VMware’s. As you can guess, that group is implied in several initiatives to bring interoperability to administrators. One of the main initiatives is CIM, built to dynamically discover and manage resources. A useful interface… And guess what??? Who is the only OS provider implementing it??? Our dear Microsoft for its Windows products ( shipped by default with Seven, server 2008… ).

Thus, who is doing the most for interoperability?…