.NET Enterprise Services Technologies : Application Blocks and Software Factories

.NET provides several resources designed to provide generic processing logic and guidance based on best practices. Application Blocks and Software Factories collectively represent these resources.

Application Blocks

When developing different services, there are utility or infrastructure functions that are commonly required by multiple solutions, regardless of the nature of their business logic.

Some examples of cross-cutting utility logic include:

• exception management

• data access

• logging and instrumentation

• authentication and authorization

SOA Principles & Patterns Application Blocks are directly comparable to out-of-the-box utility services that result from the application of Utility Abstraction  and Agnostic Context . They are so generic that when Domain Inventory  is applied to a given enterprise, they can be utilized within a cross-domain scope, as per Cross-Domain Utility Layer .

Normally, we would attempt to build a series of utility services to encapsulate these types of logic so as to make them reusable and recomposable in support of multiple service-oriented solutions.

Over the years, the Patterns and Practices Group at Microsoft has identified common bodies of utility logic and packaged them into a series of reusable components called Application Blocks.

Note

The “Patterns & Practices Group” at Microsoft was introduced to develop reusable open-source libraries to solve common infrastructure tasks and thereby bootstrap the development process. Several members of this group contributed patterns to the SOA Design Patterns book. For more information see http://msdn.microsoft.com/practices/.

Application Blocks are reusable components used to address common challenges in enterprise software development. They encapsulate the best practices and development guidelines and are available as Visual Studio projects with source code. Application Blocks are also available as compiled binaries that can be directly included in development solutions. The benefits provided by Application Blocks echo many of the strategic goals and benefits of service-oriented computing in general:

• modular development and reusability for increased ROI

• standardization of the development platform and the utility service layer

• significant increase in developer productivity and overall responsiveness

• enable project teams to focus more on business logic rather than low-level mechanics

• establish a healthy level of decoupling between the utility logic and business logic

• improve effectiveness of service governance

The available Application Blocks are listed in Table 1.

Table 1. A list of available Application Blocks.

Application Block	Description
Exception Handling	used to implement consistent exception handling policies in logical application tiers
Security Application	performs authentication, authorization, role membership checking, and profile access
Data Access	used to create, test, and maintain the data access layer (arguably the most commonly used block)
Caching Application	provides a flexible and extensible caching mechanism (can be used on the server-side and client-side)
Smart Client Application	used to build modular smart client applications
Configuration Application	used to simplify the ability to read and write configuration information from a variety of data sources
Cryptography Application	simplifies introducing cryptographic functionality in .NET services (abstracts DPAPI, symmetric encryption and hashing, and uses a configuration tool to simplify key management)
Logging and Instrumentation	allows services to be “instrumented” with logging and tracing calls

Note

The collection of all the Application Blocks listed in Table 1, with the exception of the Smart Client block, is referred to as the Enterprise Library. It is important to note that the Enterprise Library and the Application Blocks are not a part of the .NET framework. They follow an open source licensing model and are not directly supported by Microsoft.

Software Factories

A Software Factory is a collection of related software artifacts, such as reusable code, components, documentation, code generators, and visual designers. Software Factories increase the quality and predictability of services developed by standardizing solution templates used for developing services. Software Factories can help establish domain-specific services with improved consistency and quality by integrating automation scenarios deeply into Visual Studio using templates and code generation.

Guidance Toolkits

Software Factories are built using the Guidance Automation Extensions (GAX) and the Guidance Automation Toolkit (GAT).

GAX allows architects and developers to automate development tasks within the Visual Studio environment and provides a runtime environment that must be installed to start working with GAT.

GAT extends the Visual Studio environment by allowing you to author integrated user experiences. The toolkit enables the automation of development activities and integrates reusable code into services. Guidance toolkits contain several components that work together to provide automation functionality, as listed in Table 2.

Table 2. Guidance automation toolkit components.

Function	Description
recipes	automate repetitive activities that a developer would usually perform manually to reduce errors and increase consistency
actions	units of work defined by a sequence of recipes
wizards	walks developers through one or more pages gathering values and is associated with a recipe that is used to gather values for the recipe
type converters	validate the value of a field and are used to convert them to the representation used by the recipe
Visual Studio templates	used to create Visual Studio solutions and add projects (templates can be associated with recipes, which in turn are associated with wizards)

Web Services Software Factory

When working with WCF, it is common to run into decision points around when to use a data contract, when to use a message contract, and how to determine the relationship between these contracts. The Web Services Software Factory provides guidance on these issues. It is a part of Microsoft’s Software Factory initiative and provides guidance packages that help build solutions based on Web services. The ideas around using data contracts, message contracts, and service contracts are not difficult, but using these technologies in a consistent and uniform way is critically important.

Specifically, this Software Factory contains guidance packages for:

• ASMX

• WCF

• DataAccess Layer

• WS-Security using ASMX

The scope of the individual guidance packages ranges from the service proxy to the database access layer. The Service Factory includes guidance for designing messages and service entities, mapping message entities to business entities, persisting the business entity into the database, security, and exception management.

The Web Service Software Factory supports wizard-driven development of data contracts, message contracts, and service contracts. Data contracts are reusable artifacts in a project, whereas message contracts are not reusable and are specific to the operation they are being received and sent from. This Service Factory further supports the use of SOAP faults by simplifying the creation of fault contracts and attaching the fault contracts to services.

As shown in Figure 1, the Web Service Software Factory organizes solutions into the service layer, business layer, and resource access layer.

Figure 1. The service layer is further decomposed to contain service contract, service implementation, data contract, and fault contract projects. Service Factory provides a “create service implementation” recipe that creates the actual implementation. The business layer contains business-centric artifacts and the resource access layer is primarily used to abstract data access logic.