Enterprise Library Building an Application Block

1
Enterprise LibraryBuilding an Application Block

• Ed Jezierski
• Solution ArchitectScott Densmore
• Software Engineer
• Ron JacobsProduct Manager

2
Agenda

• Architectural Guidance from patterns practices
• Application Blocks
• Enterprise Library Vision
• Enterprise Library Application Blocks
• Configuration
• Cryptography
• Data Access
• Security
• Demonstration
• Questions

• Logging Instrumentation
• Exception Handling
• Caching

3
patterns practicesArchitecture Guidance for
the Enterprise
Proven Based on field experience Authoritative
Offer the best advice available
Accurate Technically validated and tested
Actionable Provide the steps to success
Relevant Address real-world problems based on
customer scenarios
Available online http//www.microsoft.com/practi
ces Books available http//www.amazon.com/pract
ices
Application Blocks
Patterns
Reference Architectures
Atomic solutions to recurring problems
Sub-system-level guidance for common services
System-level guidance for common customer
scenarios
D
A
D
I
D
A
D
I
A
A
D
D
I
I
Guides Guidance for broad horizontal topics such
as security, performance, deployment and
operations
4
Sound familiar?

• Having similar code pasted throughout your
  applications
• Writing components to enable and encourage
  reusethen rewriting them to meet specific
  application needs
• Having components that should work well together,
  but
• Each component mandating inconsistent
  requirements on the consuming application
• Longing for a way to future-proof your software
  library

5
Enterprise Library Philosophy

• Consistency
• Apply consistent design patterns and
  implementation approaches
• Extensibility
• Include extensibility points allowing developers
  to customize the behavior of the blocks by
  plugging in their own code or customize by
  directly modifying source code
• Ease of Use
• Leverage a graphical configuration tool
• Provide a simpler installation procedure
• Include clear and complete documentation and
  samples
• Integration
• Application blocks should be designed to work
  well together and tested to make sure that they
  do. But it should also be possible to use the
  application blocks individually

6
Enterprise Library v1
Caching
Exceptions
Legend
Security
Data Access
Logging
Dependency
Plug-in
Crypto
Configuration
Config Tool
7
Enterprise Library Vision
pp blocks
Partner blocks
Customer blocks
Block Specification
Community blocks
8
Elements of an Application Block

• Core functionality
• Pluggable providers
• Factories
• Configuration
• Unit tests
• Quick Starts
• Guidance and reference documentation

9
Core Functionality

• Central to its operation
• May be influenced via configuration settings, but
  basic behavior cannot be changed without source
  code modifications
• Often internal, but when exposed to an
  application, it is typically provided via a
  single class, interface, or facade
• Its OK to have core functionality not
  everything must be replaceable or even
  configurable!

10
Core Functionality Examples

• Caching
• Cache implementation (hashtable) not exposed
• Scavenging algorithm not exposed
• Cache manager exposed as a class
• Exception Handling
• Exception policy exposed as a class with single
  public static method (HandleException)
• Logging and Instrumentation
• Log filters not exposed

11
Pluggable Providers

• Associated with an application block capability,
  defined by a provider type.
• Caching Backingstore
• Data Access Database
• Exception Handling Exception Handler
• A provider is a specific implementation of a
  provider type. Each application block includes
  at least one provider implementation of each
  provider type
• Caching Database and isolated storage
  backingstores
• Data Access SQL, DB2 and Oracle databases

12
Pluggable Providers

• Decouples the application block's core
  functionality from specific implementation,
  achieving the following goals
• Variability
• Extensibility
• Encapsulation
• Portability across environments
• Minimized coupling between application blocks
• Specified in configuration data with type
  information and a name

13
Provider Implementations and Configuration

• Providers typically allow for configuration of
  each specific implementation
• Example the replace exception handler has a
  configuration setting for the new exception type
• The abstract base class ConfigurationProvider
  defines the contract for initializing a provider
  with configuration information
• Decision point create a new provider
  implementation, or configuration property of an
  existing implementation

14
Provider Factories

• Uses Plugin Fowler pattern to create providers
• Neither applications nor application blocks
  require information about specific implementation
  of provider
• Specific implementation to be constructed
  determined by configuration settings
• Abstract base class (ProviderFactory) in
  Configuration Application Block contains code to
  instantiate configurable providers

15
Provider Factories

• Static method to create provider objects
• Allow for creation of default provider (as
  specified by configuration settings)
• Allow for creation of named provider

' Create the default database instance Dim db As
Database DatabaseFactory.CreateDatabase() '
Use a named instance to map to configuration Dim
salesDb As Database DatabaseFactory.CreateDataba
se("Sales")

• Allows you to reconfigure and execute the
  application without recompiling

16
Configuration

• Allows you to easily adapt the application block
  to meet the needs of different enterprise
  scenarios
• Creation and editing of configuration settings is
  done with the Configuration Console
• Configuration settings may be defined for an
  application blocks core functionality and for
  each provider type

17
Configuration

• Using configuration settings to adapt an
  application block to a particular situation has
  two advantages
• Characteristics of an application block can be
  configured by different people at different times
  in the application life cycle
• The application block can be incrementally
  adapted for increasingly complex situations

18
Configuration

• Runtime configuration
• Object graphs that represent configuration
  settings
• Configuration Application Block reads settings
  from storage and returns objects to application
  block
• XML File Storage Provider and Transformer require
  that objects be serializable
• Design-time configuration
• Allow settings to be displayed, changed and
  validated using the Configuration Console

19
Design-time and Runtime Relationship
20
Design-Time Configuration

• Based upon System.ComponentModel
• Configuration node is of type Component
• The Configuration Console provides the Site
• Services are available through Config Block
• Configuration node classes for each node in the
  configuration tree
• Each node determines the properties to be
  displayed when node is selected
• Validation rules can be included for any property

21
Configuration Nodes

• Determine how the Configuration Console displays
  the hierarchy of configuration nodes
• Determine which/how properties are exposed in the
  graphical interface
• Enable the Configuration Console to validate that
  the values a user assigns to an application
  block's properties are appropriate
• Can contain references that point from one
  application block to another (such as an
  authorization database that points to a database
  instance)
• Contain references to the runtime data classes

22
Configuration Design Manager

• Implements IConfigurationDesignManager interface
• Allows an application block to be added to an
  applications configuration hierarchy
• Creates menu items and commands that are invoked
  as user interacts with the Configuration Console
  to configure the application block
• Responsible for loading and saving configuration
  data
• Assembly must be located in same directory as
  Configuration Console executable

23
Configuration Application Block Support

• The Configuration Application Block provides much
  of the plumbing for runtime and design-time
  configuration

24
Configuration Console
Properties
Configuration Nodes
Validation Error
25
Unit Tests

• Verify functionality of application block
• Verify that modifications to application block
  have not cause regression
• Enterprise Library developed using Test Driven
  Development (TDD)

26
Quick Starts

• Demonstrate common scenarios of application block
  usage
• Display output indicating what happened under
  the covers
• Detect common errors (e.g. user didnt perform
  required setup) and display useful information
• Goal Open solution, hit F5, and see it run

27
Documentation

• Integrated into Visual Studio
• Guidance
• Introduction and goals
• Developing applications using the application
  block
• Design of the application block
• Extending the application block
• Deploying the application block
• Quick start walkthroughs
• Reference API
• Public and protected
• Summaries, parameters and return values

28
A Simple Example Hello World Application Block

• Client application can use the application block
  to return a greeting for a specified user
• The implementation of how the greetings are
  returned is encapsulated in a greeting provider
• An application can use multiple greeting
  providers, each identified by a unique name
• The Configuration Console is used to select the
  default greeting provider, used when the client
  does not specify a name for the provider
• Each greeting provider has a default message, set
  by the Configuration Console

29
Hello World Application Block Core Functionality

• Minimal to keep things simple
• Includes the interface definition
  IGreetingProvider, which all greeting providers
  must implement
• Includes the class HelloWorldConfigurationView
• Derives from ConfigurationView
• Exposes the runtime configuration settings
  required by the application blocks providers
• Passed to the Initialize method of each provider
  when it is created

30
Hello World Application Block Configuration View

• Initialized with ConfigurationContext

public virtual GreetingProviderData
GetGreetingProviderData(string name) //
HelloWorldSettings is our runtime configuration
object HelloWorldSettings settings
GetHelloWorldSettings() return
settings.GreetingProvidersname

• Returns configuration data required by
  application block

public virtual string GetDefaultGreetingProviderDa
taName() HelloWorldSettings settings
GetHelloWorldSettings() return
settings.DefaultGreeter
31
Hello World Application Block Providers

• Text greeting provider
• Returns plain text greeting for specified user
• Greeting for a user is determined by
  configuration settings
• Includes configuration design-time support to
  allow greetings to be entered and validated
• Custom greeting provider
• Allows user to select the FQTN of a class that
  implements IGreetingProvider
• Configuration is provided via a property bag of
  name-value pairs (no design-time support)

32
Hello World Application Block Runtime
Configuration

• Requirements
• Block allows multiple greeting providers
• Each greeting provider has a name
• Text greeting provider can have multiple
  greetings
• A greeting is name and a message
• Configuration Information is represented as
  serializable classes

33
Runtime Configuration Data

• lt?xml version"1.0" encoding"utf-8"?gt
• lthelloWorldConfigurationgt
• ltxmlSerializerSection
• type"Microsoft.Practices.Samples.HelloWorld.C
  onfiguration.HelloWorldSettings,
• Microsoft.Practices.Samples.HelloWorld,
  Version1.0.0.0, Cultureneutral,
• PublicKeyTokennull"gt
• lthelloWorldSettings xmlnsxsd"http//www.w3.o
  rg/2001/XMLSchema"
• xmlnsxsi"http//www.w3.org/2001/XMLSchema-
  instance" defaultGreeter"Casual Greetings"
• xmlns"http//www.microsoft.com/practices/sa
  mples/08-31-2004/helloworld"gt
• ltgreetingProvidersgt
• ltgreetingProvider xsitype"TextGreetingPr
  oviderData" name"Casual Greetings"
  defaultGreeting"Hello World!"gt
• ltgreetingsgt
• ltgreeting name"John" message"Hi
  John." /gt
• ltgreeting name"Maria" message"Ciao
  Maria!" /gt
• lt/greetingsgt
• lt/greetingProvidergt
• lt/greetingProvidersgt
• lt/helloWorldSettingsgt
• lt/xmlSerializerSectiongt

34
Runtime Configuration Classes

• HelloWorldSettings
• Includes configuration section name, collection
  of providers, and default greeting provider
• GreetingProviderData (base class),
  TextGreetingProviderData, CustomGreetingProviderDa
  ta
• Common settings and settings specific to
  providers
• TextGreetingDataCollection
• Collection of text greetings
• TextGreetingData
• Name and message

35
Configuration Application Block Runtime Support
36
Runtime Configuration Class Serialization

• Root object serialization

XmlRoot("helloWorldSettings", NamespaceHelloWorl
dSettings.ConfigurationNamespace) public class
HelloWorldSettings

• Collection serialization

XmlArray("greetings", NamespaceHelloWorldSetting
s.ConfigurationNamespace) XmlArrayItem(Typetype
of(TextGreetingData), NamespaceHelloWorldSettings
.ConfigurationNamespace) public
TextGreetingDataCollection Greetings get
return this.greetings
37
Runtime Configuration Class Serialization

• XML include types for base classes

XmlType("greetingProvider", NamespaceHelloWorldS
ettings.ConfigurationNamespace) XmlInclude(typeo
f(CustomGreetingProviderData)) XmlInclude(typeof
(TextGreetingProviderData)) public abstract
class GreetingProviderData ProviderData
38
Hello World Design-Time Configuration

• Required to allow the application block to be
  configured with the Configuration Console

39
Hello World Client

• Create provider

// Create default greeting provider (determined
by configuration) IGreetingProvider
defaultProvider GreetingFactory.GetGreetingProvi
der() // Create named instance IGreetingProvider
formalProvider GreetingFactory.GetGreetingProvi
der("Formal Greetings")

• Call provider methods

string greeting defaultProvider.SayGreeting(Joh
n)
40
Additional Resources

• Improving Web Application Security
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/dnnetsec/html/ThreatCounter.asp
• Improving .NET Application Performance and
  Scalability
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/dnpag/html/scalenet.asp
• Application Architecture for .NET
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/dnbda/html/distapp.asp
• PatternShare.org
• Enterprise Library Communityhttp//go.microsoft.c
  om/fwlink/?linkid39209clcid0x09
• www.ronjacobs.com
• Slides
• Tech Tips
• Podcasts

41
Announcing Enterprise Library 1.0

• http//www.microsoft.com/practices

Download it Today!
42
Patterns and Practices Live!

• Slides, Hands On Labs, On Demand Webcasts
• Upcoming Live Webcasts
• 3/28 Building your own block
• 3/31 Enterprise Library Applied
• 4/12 Global Bank Baseline Architecture
• 4/14 Updater Application Block v2

http//www.pnplive.com
43
http//www.microsoft.com/practices