Agile Web Development with the Castle Project

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Agile Web Development with the Castle Project

• 15/05/2008, Skills Matter
• Gojko Adzic
• gojko_at_gojko.com
• http//gojko.net

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Why should you care?

• Increases programmer productivity
• Allows us to apply modern programming practices
  (AoP, DI)
• Provides a solid foundation for agile web
  programming
• Brings best ideas from Spring/Java and Ruby on
  Rails to the .NET world

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What is it?

• Several loosely-coupled components
• Windsor IoC and AOP container
• ActiveRecord data-access
• Monorail MVC
• Bunch of other libraries (Dynamic Proxy)
• You can use them separately
• Even more productive when used together

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But it is a RC!

• A bad marketing decision
• RC because it is work in progress, not because it
  is unstable
• Ive used it in production for about two years
  now, no problems at all

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Application framework

• Mix between Spring and RoR
• Integrates with almost anything
• Lightweight, short learning curve
• Convention over configuration
• Lots of helpers and utils
• Nothing is enforced

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What do we get?

• Very efficient programming model
• Almost all the plumbing is already there
• Testable web apps (everything below the UI)
• Will age gracefully

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What do we lose?

• ASP.NET components
• MS stamp of approval
• this is not .NET attitude might be a problem
• Need more training, probably cannot hire people
  off the street

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ActiveRecord

• Simple O/R
• Classtable
• Objectrow
• Propertycolumn value
• Configuration by code attributes
• Uses NHibernate under the hood

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ActiveRecord ()

• Incredibly simple O/R mapper
• Simplifies NHibernate configuration for common
  cases
• Unit-testable
• Supports validation
• Great integration with MVC engine

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ActiveRecord (-)

• Bad separation of concerns
• It represents domain code
• It also dictates storage
• Generally better for green-field development

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Key stuff to remember for AR

• the class needs to be annotated with attributes
• create a dedicated assembly for ActiveRecord
  types
• beware of using names that are DB keywords
• use ActiveRecordValidationBase if you want
  validations to work

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Key stuff about AR testing

• Kill the initialisation flag in unit tests to
  allow re-initialisation
• ActiveRecord can generate the schema for you, but
  this is not perfect
• Dont forget to flush
• Try to reload objects and verify properties

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You dont have to use AR!

• Castle integrates with NHibernate and IBatis
  nicely
• Data mapping and validation works on plain CLR
  objects
• A bit more code, but much more flexibility

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Monorail

• MVC based on Rails
• Smart url mapping
• Classfolder part of the URL
• Methodfile part of the URL
• Takes care of all HTTP plumbing
• Flexible view engines

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Monorail Controllers

• Basic building blocks of Monorail
• Responsible for workflow and session
• Group related workflow steps
• SmartDispatcherController binds GET/POST
  variables to method arguments
• No formatting!

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Monorail Actions

• Perform a single step in the workflow
• Prepare data for the view (PropertyBag)
• (optionally) Select the view
• Chaining/Reuse patterns
• Call method
• RenderView
• RedirectToAction
• Use Flash to pass messages while redirecting

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Monorail Views

• Data formatting
• Simple scripting, related to UI Formatting
• No business code, no workflow code

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5-minute Velocity guide

• varname (or varname.property)
• if / end
• parse to include other scripts
• Partial templates with foreach

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Monorail Helpers

• Utilities for formatting
• Generating UI code
• Forms
• Ajax (prototype, js proxies)
• Or roll your own

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Monorail Layouts

• Master pages or templates
• Use childContent to embed views
• Use siteRoot for relative paths
• Set by attribute on class or method

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Monorail Components

• Reusable parts of the layout
• Menu bars
• Shared functional parts
• Alternatives
• Use Helpers for formatting
• Use partial templates and loops for repeatable
  content
• Can also be done with Ajax DIVs

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Monorail Filters

• Actions to execute before or after controller
  actions
• Simple web AOP
• Authorisation
• Logging

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Monorail Rescues

• View called on error
• Specify on whole controller or on action
• Generic or bound to an exception
• Individual actions do not have to worry about
  error handling in most cases -gt less code

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Monorail and ActiveRecord

• Extend ARSmartDispatcherController
• Data-mapping to load record objects
• ARFetch
• ARDataBind
• Scaffolding
• Not the cleanest solution storage and business
  logic mixed but very productive

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Monorail Unit Testing

• Use BaseControllerTest from Castle.MonoRail.TestS
  upport
• Call InitController to prepare the environment
• Test the class like any other
• Inject services into containers so that you can
  test them in isolation

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Monorail ()

• HTTP Request plumbing
• Smart dispatching, data binding
• Convention over configuration
• Unit testing
• Fantastic AR integration
• Several layout engines

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Monorail (-)

• Attribute based layout and area selection
• Hashmap for view properties
• I have mixed feelings about this
• Windsor integration a bit too complicated
• Maybe use service locator pattern in this case

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Key stuff to remember (MR)

• Override the web app to initialise AR
• Use data-binding to load whole objects
• Put stuff into PropertyBag to pass to a view
• layouts are page templates
• Use the Flash to simplify workflow
• Learn standard helpers and use them

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Windsor/MicroKernel

• MicroKernel is an IoC/AOP framework
• Windsor loads configuration from files
• Manage component pooling and lifestyles
• Provide interception

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Windsor Components

• Components are application building blocks
• They can provide a service
• Constructor arguments and properties can be
  automatically resolved
• Constructor args are mandatory
• Properties are optional
• Lazy Loaded!

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Windsor Facilities

• Extend the framework by hooking to component
  events
• Attaching interceptors
• Integrating with 3rd party libraries
• Standard Facilities
• Automatic transaction management
• Logging
• Starting/stopping components

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WindsorMonorail

• Inject services into controllers
• Add IContainerAccessor to web app, initialise ONE
  Windsor context on start
• Makes controller code even more simple, but
  complicates configuration
• Alternative is to use service locator

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Windsor Key stuff to remember

• Services are automatically resolved by interface
• Components are lazy loaded
• Initialise only one context per application
• Beware of cyclic dependencies
• Use Features and Interceptors for AOP

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Why I like Castle

• Makes simple things very easy, but allows doing
  complex stuff as well
• Co-operates with other popular libraries
• Convention over configuration
• ARMR Great for prototyping
• Allows us to cover big parts of web code with
  unit tests

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Where next?

• ALT.NET beer meeting straight away
• 21/05 MS MVC_at_DNUG http//dnug.org.uk/
• www.castleproject.org
• EvilLink demo app http//gojko.net