Understanding COM+

Q8M1 – SC Dudy Fathan Ali S.Kom
Distributed Application Development
Q8M1
Dudy Fathan Ali, S.Kom (DFA)
2017
CEP - CCIT
Fakultas Teknik Universitas Indonesia

Additional Documents
bit.ly/4sc1-repo
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Objectives
Identify COM+
Create COM+ serviced components
Explore COM+ applications

Introducing COM+
o Earlier distributed applications were based on DCOM.
o DCOM-based applications do not provide features such as secure
communication and reliable data transfer.
o To include such features in the distributed applications, you need to
implement COM+.

Evolution of COM+
o Single-tier applications do not provide code reusability.
o COM was introduced to provide code reusability.
o COM had the following limitations:
o It does not allow a client application residing on a separate
computer to access a component.
o It does not provide features such as security and consistency of
data.
o These limitations led to the development of DCOM.

Evolution of COM+ (contd.)
o DCOM:
o Allows developers to create a component that can be accessed by a
client application residing on a separate computer.
o Provides features such as security and platform independence that
are required in the distributed application architecture.
o DCOM does not provide features such as reliable data transfer,
enhanced performance, and optimum memory consumption required in
the distributed application architecture.
o This led to the development of COM+.

COM+ Services
o COM+ provides various services that enable COM developers to develop
scalable and robust distributed applications.
o Some of the COM+ services are:
o Just-in-time activation
o Role-based security
o Synchronization
o Object pooling
o Transactions
o Queued components

COM+ Services (contd.)
o The just-in-time (JIT) activation service:
o Enables optimum use of server resources.
o Can be implemented in a COM+ serviced component, as shown in
the following code snippet:
[JustInTimeActivation]
public class MyClass : ServicedComponent
{
//class body
}

o The role-based security service:
o Is used to secure distributed applications.
o Provides role-based access to the components.
[SecurityRole("Manager", SetEveryoneAccess=false)]
{
//class body
}

o The synchronization service:
o Enables you to manage multiple client applications accessing a
COM+ serviced component, simultaneously.
o Prohibits more than one application to access a component at a
particular point in time.
[Synchronization(SynchronizationOption.Required)]
{
//class body
}

o A transaction:
o Enables a component to maintain data integrity and consistency by
grouping various related operations as an atomic unit.
o Is successful only when all the operations contained in the atomic
unit are completed successfully.
[Transaction(TransactionOption.Required)]
{
//class body
}

o Message queuing service:
o Enables a client to send a message to a COM+ serviced component
even if the component is not available due to network connectivity.
[assembly: ApplicationQueuing(Enabled = true,
QueueListenerEnabled = true)]
namespace MyComponent
{
public class Class1:ServicedComponent
{
//class body
}
}

Creating COM+ Serviced Components
o Components that use COM+ services are called COM+ serviced
components.
o COM+ serviced components are derived from the .NET base class
ServicedComponent present in the System.EnterpriseServices
namespace.
o To implement COM+ services in a .NET component, you need to:
o Configure the component.
o Register the component.

Configuring a .NET Component
o To implement COM+ services in a .NET component, you need to inherit
the ServicedComponent class present in the
System.EnterpriseServices namespace, as shown in the
following code snippet:
using System.EnterpriseServices;
namespace MyComponent
{
public class MyComponentClass:ServicedComponent
{
//class body
}
}

Registering a .NET Component
o To enable a client application to access a COM+ serviced component,
you need to register it in the Component Services tool.
o You can register a component in the Component Services tool by using
any one of the following ways:
o Manual registration
o Programmatic registration
o Dynamic registration

Summary
o In this session, you learned that:
o COM+ is a programming model that provides a number of features
such as security, queuing, and transactions.
o A component that implements the services provided by COM+ is
known as a COM+ serviced component.
o Some of the services provided by COM+ are:
o Just-in-time activation
o Role-based security
o Synchronization
o Object pooling
o Transactions
o Queued components

Summary
o COM+ serviced components are derived from the .NET base class,
ServicedComponent present in the System.EnterpriseServices
namespace.
o The three ways in which a COM+ serviced component can be registered
are:
o Manual registration
o Programmatic registration
o Dynamic registration
o The COM+ serviced components that are related to each other and
perform similar functions can be stored in a COM+ application.

Summary
o The various types of COM+ applications are:
o Library applications
o Server applications
o Application proxies
o COM+ preinstalled applications

Exercise (contd.)
o Sam, a manager at Imperial Bank, is constantly required to calculate the
interest amounts for the loans acquired by their customers. The bank
has the following schemes to grant loan to the customers:
o A five-year scheme with 5% rate of interest.
o A three-year scheme with 10% rate of interest.
o A two-year scheme with 15% rate of interest.
o You, as a software developer, need to create a COM+ serviced
component that calculates the interest and the total amount to be paid
by the customer at the end of the loan duration.

Exercise (contd.)
o In addition, you need to create a client application that uses the COM+
serviced component. The client application should accept the customer
name, the loan amount, and the number of years and display the total
amount to be paid by the customer at the end of the period.
o To calculate the interest and the total amount by using a COM+ serviced
component and to display the amount by using a client application, you
need to perform the following tasks:
o Create a COM+ serviced component.
o Register the COM+ serviced component.
o Create a client application.
o Execute and verify the client application.

Exercise (contd.)
bit.ly/4sc1-repo
Upload your answers in .rar extension to:

Thank You!
Dudy Fathan Ali, S.Kom
dudy.fathan@eng.ui.ac.id

Understanding COM+

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