Introductory Example Using the COM+ Administration Catalog

When programmatically using the COM+ Administration catalog, you typically carry out the following general steps (not given in a strict order here):

• Open a session with the COM+ catalog on the local machine. Optionally, connect to the COM+ catalog on a remote machine.
• Perform actions such as starting or stopping services—actions that don't pertain to a particular COM+ application.
• Perform actions such as installing or exporting COM+ applications, or installing components into applications—actions that pertain to reading from or writing to files.
• Add new items to collections, such as creating a new COM+ application by adding a new item to the "Applications" collection.
• Set or get properties on an item in a collection.
• Save or discard pending changes to the catalog.
• Handle any errors that might occur.

To show what these steps look like when you use the COMAdmin objects, a Microsoft Visual Basic example is provided below. It briefly illustrates some of the typical steps described above, such as locating collections, enumerating through a collection to retrieve an item, and setting properties on that item.

In the example below you will perform the following actions:

1. Create a new COM+ application, "MyHomeZoo".
2. Install some components, Cat and Dog, into the application. Both components are contained in a single DLL that must already exist: MyZoo.dll.
3. Configure role-based security for the application by defining two roles: ZooKeeper and AllergicToCats.
4. Assign the ZooKeeper role access to the entire application.
5. Assign the AllergicToCats role access to only the Dog component.
6. Turn on security properties so that role checking will be enforced for the application.
7. Export the MyHomeZoo application to a file so that it can be installed on other computers.

To use this example from Visual Basic, add a reference to the COM+ Admin Type Library.

Function SetupMyZoo() As Boolean  ' Return False if any errors occur.

    '  Initialize error handling for this function.
    SetupMyZoo = False 
    On Error GoTo My_Error_Handler

    '  Open a session with the catalog.
    '  Instantiate a COMAdminCatalog object. 
    Dim objCatalog As COMAdminCatalog
    Set objCatalog = CreateObject("COMAdmin.COMAdminCatalog")

    '  Create a new COM+ application.
    '  First get the "Applications" collection from the catalog.
    Dim objApplicationsColl As COMAdminCatalogCollection
    Set objApplicationsColl = objCatalog.GetCollection("Applications")

    '  Add a new item to this collection. 
    Dim objZooApp As COMAdminCatalogObject
    Set objZooApp = objApplicationsColl.Add

    '  The "Applications" collection determines the available properties.
    '  Set the "Name" property of the new application item. 
    objZooApp.Value("Name") = "MyHomeZoo"

    '  Set the "Description" property of the new application item. 
    objZooApp.Value("Description") = "My pets at home"

    '  Save changes made to the "Applications" collection. 
    objApplicationsColl.SaveChanges

    '  Install components into the application.
    '  Use the InstallComponent method on COMAdminCatalog. 
    '  In this case, the last two parameters are passed as empty strings.
    objCatalog.InstallComponent "MyHomeZoo","MyZoo.DLL","","" 

    '  Define the roles ZooKeeper and AllergicToCats 
    '  by adding them to the "Roles" collection related to MyHomeZoo. 
    '  First get the "Roles" collection related to MyHomeZoo.
    '  Use the GetCollection method on COMAdminCatalogCollection,
    '  passing in the name of the desired collection, "Roles", 
    '  and the Key property value of objZooApp.   
    '  The Key property uniquely identifies the object, serving
    '  here to distinguish the "Roles" collection related 
    '  to MyHomeZoo from that of any other application. 
    Dim objRolesColl As COMAdminCatalogCollection
    Set objRolesColl = objApplicationsColl.GetCollection("Roles", objZooApp.Key)

    '  Add new items to this "Roles" collection. 
    Dim objZooKeeperRole As COMAdminCatalogObject
    Dim objAllergicToCatsRole As COMAdminCatalogObject
    Set objZooKeeperRole = objRolesColl.Add
    Set objAllergicToCatsRole = objRolesColl.Add

    '  Set the "Name" for the new items.
    objZooKeeperRole.Value("Name") = "ZooKeeper" 
    objAllergicToCatsRole.Value("Name") = "AllergicToCats" 

    '  Save changes made to any items in this "Roles" collection. 
    objRolesColl.SaveChanges

    '  Assign the AllergicToCats role to the Dog component to 
    '  restrict its scope of access. (The ZooKeeper role, if assigned
    '  only at the application level, can access the whole application.)
    '  First get the "Components" collection related to MyHomeZoo.
    '  Use the GetCollection method on COMAdminCatalogCollection,
    '  passing in the name of the desired collection, "Components", and
    '  the Key property value of objZooApp. 
    Dim objZooComponentsColl As COMAdminCatalogCollection
    Set objZooComponentsColl = objApplicationsColl.GetCollection("Components", objZooApp.Key) 

    '  Find the Dog component item in this "Components" collection.
    '  First Populate the collection to read in data for all its items. 
    objZooComponentsColl.Populate

    '  Enumerate through the "Components" collection 
    '  until the Dog component item is located. 
    Dim objDog As COMAdminCatalogObject 
    For Each objDog in objZooComponentsColl
        If objDog.Name = "Dog" Then 
            Exit For
        End If
    Next 
    '  Set the role checking property at the component level for Dog.
        objDog.Value("ComponentAccessChecksEnabled") = True 

    '  Save these changes.
        objZooComponentsColl.SaveChanges
    '  Get the "RolesForComponent" collection related to the 
    '  Dog component, using the Key property of objDog. 
    Dim objRolesForDogColl As COMAdminCatalogCollection 
    Set objRolesForDogColl = objZooComponentsColl.GetCollection("RolesForComponent", objDog.Key) 

    '  Add a new item to this "RolesForComponent" collection. 
    Dim objCatSneezerRole As COMAdminCatalogObject
    Set objCatSneezerRole = objRolesForDogColl.Add

    '  Set the "Name" of the new item to be "AllergicToCats". 
    objCatSneezerRole.Value("Name") = "AllergicToCats" 

    '  Save changes made to this "RolesForComponent" collection. 
    objRolesForDogColl.SaveChanges

    '  Now set properties to enforce role-based security. 
    '  First set role-based security at the application level.
    objZooApp.Value("ApplicationAccessChecksEnabled") = True 
    objZooApp.Value("AccessChecksLevel") = COMAdminAccessChecksApplicationComponentLevel 

    '  Save these changes.
    objApplicationsColl.SaveChanges

    '  Finally, export the new configured MyHomeZoo application to an 
    '  MSI file, used to install the application on other machines.
    '  Use the ExportApplication method on COMAdminCatalogObject.
    objCatalog.ExportApplication "MyHomeZoo", "c:\Program Files\COM applications\MyHomeZoo.MSI", 4

    '  Exit the function gracefully.
    SetupMyZoo = True

My_Error_Handler:
    If Not SetupMyZoo Then
        MsgBox "Error # " & Err.Number & " (Hex: " & Hex(Err.Number) & ")" & vbNewLine & Err.Description
    End If
    objCatSneezerRole = Nothing
    objRolesForDogColl = Nothing
    objDog = Nothing
    objZooComponentsColl = Nothing
    objAllergicToCatsRole = Nothing
    objZooKeeperRole = Nothing
    objRolesColl = Nothing
    objZooApp = Nothing
    objApplicationsColl = Nothing
    objCatalog = Nothing
Exit Function

Related topics

COM+ Administration Operations Within Transactions

Handling COM+ Administration Errors

Overview of the COMAdmin Objects

Retrieving Collections on the COM+ Catalog

Setting Properties and Saving Changes to the COM+ Catalog