COM+ Programming

PRADEEP TAPADIYA is a Program Manager and Lead Software Engineer for the OpenView ManageX Group of Hewlett-Packard in Roseville, CA. He started developing COM-based applications in 1996 and is currently involved with developing a suite of systems management applications for Windows NT and 2000 using DCOM. Tapadiya holds a doctoral degree in computer science from Texas A&M University.

I. THE FOUNDATION.

1. The Component Model.


Component Reusability. Traditional Software Reusability. Reference Hardware Components. Simulation Program. Role of the Linker and the OS Loader. Dynamic Link Library. Fixing a Defect. Hardware Component Model. Separating Interface from Implementation. Common Aspects of C++ Language. Virtual Methods in C++ and Memory Layout. Interface as an Abstract Base Class. Dynamic Selection of a Component. Extending the Interface Functionality. Managing the Lifetime of an Object. Optimizations. Error Reporting. The Essence of COM. Summary. References.

2. Designing Interfaces.


Why a New Language? Programming Language Independence. Remote Transparency. Interface Definition Language (IDL). IDL Attributes. IDL Design Goals. Remote Transparency. Programming Language Independence. Semantic Information. Standardized Calling Conventions. Memory Management. Identification. Compiled Type Information. Component Identification. Processing IDL Files. IDL File Structure. The Preprocessor Section. The Interface Section. The Type Library Section. IDL Syntax. Defining Interface Methods. Defining IDL Interfaces. Defining COM Classes. Defining IDL Libraries. Automation. Basic Data Types. Strings. Booleans. Variants. Safe Arrays. Automation-Compatible Interfaces. Collections and Enumerations. Interfaces and Marshaling. Memory Management. Organizing Multiple IDL Files. Putting It All Together. Summary. References.

3. Components.


From C++ to COM—A Quick Tour. Implementing Interfaces. Method Implementation. Instantiation Logic. The TV Client. The COM+ Catalog. Revisiting C++ Code. Multiple Classes in a Server. Multiple Instances of a Class. Storing Configuration Information. Memory Cleanup. Implementing COM Objects. Using Multiple Inheritance. Implementing the Root Interface. ATL is Our Friend. Tear-Off Interfaces. Reusing Components. Containment. Aggregation. Error Reporting. Summary. References.

II. THE EXTENSION.

4. Essence of COM+.


Enterprise Systems. Security. Scalability. Sharing Resources. Transactions. Three-Tier Architecture. Windows DNA. COM+ = Simplified Development. Administrative Control. Transaction Services. Security Services. Synchronization Services. Queued Components. Event Service. Object Pooling. Just-In-Time (JIT) Activation. Remote Deployment. Summary. References.

5. COM+ Programming Model.


Attribute-Based Programming. The COM+ Catalog. Configuring a Component. Component Initialization. Developer-Specified Attributes. COM+ Context. Contexts and Interception. Interception and Performance. Object Context. Default Context. Call Context. Object Activation. In-Process Activation. Out-of-Process Activation (Local Host). Remote Activation (Distributed Computing). Executing in a Different Context. Summary. References.

6. Concurrency.


Multithread Programming. A Simple Example. Multithreading Issues. Apartments. Single-Threaded Apartments (STA). Multithreaded Apartments (MTA). Thread-Neutral Apartments (TNA). Configuration Settings. Activities. Apartments and Standard Marshaling. Dispatching Calls to an STA. Dispatching Calls to an MTA. Dispatching Calls to a TNA. Cross-Context Access. Developing Thread-Safe COM Code. Shared Data Conflicts. Waiting for an Event. Sharing State Across Multiple Objects. Summary. References.

7. Security.


The COM+ Security Model. Windows NT Security System Basics. Security Issues Under COM. Security Service Providers (SSPs). Security Blankets. Declarative Security. Default Settings. Application-Specific Settings. Server-Side Security Programming. Client-Side Security Programming. Impersonation Levels. Identity and Authentication Services. Client Acting as a Server. Adjusting Security for a Proxy. Summary. References.

8. Transactions.


The Stock Trader. The Database Layer. The Business Logic. The Simulation. Transaction Theory. COM+ Support for Transactions. Configuring Transactions. Programmatic Voting. The Architecture. Resource Managers. The Distributed Transaction Coordinator. Automatic Transactions through COM+. Manual Transactions. Compensating Resource Manager. Summary. References.

9. Message Queuing.


Message-Based Queuing. The Need for Queuing. Why Use MSMQ? MSMQ Overview. MSMQ Servers. MSMQ Clients. Queue Types. Queue Naming. MSMQ COM Components. Sending and Receiving Messages. Guaranteed Delivery. Responding to a Message. Sending Objects in the Message Body. Transactions. Queued Components. A Simple Phone Book Example. Queued Component Architecture. Getting a Response. Transaction Support. Summary. References.

10. Events.


Introduction. Tightly Coupled Events (TCEs). Connection Points. Receiving Messages with MSMQ Events. Loosely Coupled Events (LCEs). COM+ Events Architecture. A Simple Event Example. Transient Subscriptions. Events and Queued Components. Events and Filtering. Summary. References.

11. Scalability.


Introduction. Resource Dispensers. Just-in-Time (JIT) Activation. Object Pooling. Requirements for Poolable Objects. Asynchronous Method Calls. Asynchronous Clients. Asynchronous Servers. Canceling a Synchronous Call. COM+ Pipes. Summary. References.

12. Administration.


Overview. COM+ Administration Object Model. COMAdminCatalog Object. COMAdminCatalogCollection Object. COMAdminCatalogObject Object. Programming Considerations. Error Handling. Administrative Tasks and Transactions. Some Common Administrative Tasks. Uninstalling an Application. Installing an Application. Deploying an Application. Future Enhancements. Summary. References.

Index.