1 Model-Driven Integration Strategies Joe Berkovitz Chief Architect, Allurent Inc.
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Model-Driven Integration Strategies
Joe Berkovitz
Chief Architect, Allurent Inc.
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This talk is about…
Modelling: describing software abstractly
Integration: hooking up disparate components
Strategy: an overarching approach to a problem
Model-Driven Integration Strategy:An approach that uses abstract descriptions to drive the hookup of disparate components
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Who…
…is using SOAP web services?
…is using HTTP/XML services?
…is using RemoteObject
…is using Flex Data Services?
…is using Flash Remoting?
…is using Cairngorm?
…is using custom transport/serialization?
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Who hates writing burdensome,repetitive, error-prone code?
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The Integration Problem
Many strongly-related components and assets Value Objects
Services with VO params that return more VOs
Multiple language bindings for VOs, Services
VO Serializers and Deserializers
User Documentation
Metadata
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The Integration Problem
Many languages in play ActionScript 2
ActionScript 3
MXML
Java
C#
XSD
WSDL
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The Integration Problem
Many transport technologies SOAP Web Services
Axis
.NET
REST Web Services
XMLRPC
Flash Remoting
Flex Data Management Services
Random Custom Stuff
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Controller
My real (ugly) worldFlex Client
SOAP web services
CatalogService
OrderService
Views
SOAP/XML
ValueObjects
REST/XML
integration layer
Commerce APIs
REST web services
data access layer JavaModel
WSDL
CatalogDB
Catalog Server Commerce Server
Documentation
Process Support
VO, ServiceMetadataXML Marshaller
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Controller
Commonalities
SOAP web services
CatalogService
OrderService
Views
integration layer
Commerce APIs
REST web services
data access layer JavaModel
WSDL
CatalogDB
Catalog Server Commerce Server
Documentation
Process Support
ValueObjects
Flex Client
VO, ServiceMetadataXML Marshaller
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Commonalities (continued)
Many components encode the same information or overlap heavily
Variations: role
syntax
structure
degree of detail
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Transformation Tools
In limited realms, transformation tools are popular
They reduce the number of parallel representations
Example: Axis WSDL2Java (.NET similar)
SOAP web services JavaModel
WSDL
WSDL2Java
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or….. Java2WSDL!
SOAP web services JavaModel
WSDL
Java2WSDL
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Existing transformation tools are limited
Axis, .NET stay within their platform boundaries
xdoclet, xdoclet2 rely on annotation of Java classes, interfaces: locks into standard OOP language model
XSLT doesn't work so well for very complex iterative transforms, and has limited programmability (for non-masochists)
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Where transformations help
Across technology domains: same concept, different languages/protocols
Within technology domain: interlocking concepts, same language
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Output FilesOutput Files
GeneratorsGenerators
What Hamachi does
Language-neutral XML model description…
…is parsed according to Metamodel into an in-memory model…
…Generators pass parts of that model…
…to Velocity templates to format them into output files
Hamachi
Metamodel Generators
ModelDescription
Output Filestemplates
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Output FilesOutput Files
GeneratorsGenerators
Hamachi modules
Different projects need different models, different templates
Hamachi modules package the part that varies:
Hamachi
Metamodel Generators
ModelDescription
Output Filestemplates
Module
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Harnessing Generation with Hamachi
CatalogService
OrderService
Documentation
Process Support
Hamachi
SOAP web services JavaModel
WSDL
WSDL2Java
ModelDescription
ValueObjects
VO, ServiceMetadata
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Derived Assets for a Single Object
OrderService:OrderItemSummary addToCart()
OrderItemSummary.as
OrderItemSummary.html
Hamachi
addToCart WS endpoint OrderItemSummary.java
<complexType name="OrderItemSummary"/><wsdl:operation name="addToCart">
WSDL2Java
<ClientModelTypename=
"OrderItemSummary">
new ClassDescriptor("OrderItemSummary")
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What is a metamodel?
Models describe parts of your application OrderItemSummary is a ClientModelType in the model
OrderItemSummary.price is a Property in the model of type decimal
CatalogService is a ClientService in the model
Metamodels describe parts of your model: ClientModelType is a Class in the metamodel
ClientModelType.properties is a Property of type PropertyList
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Adding an Attribute to the ARC Model
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Model-Driven SOAP Support
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Why not just use <mx:WebService>?
Operations and request/response not strongly typed
No access to returned SOAP fault information
High overhead from parsing WSDL
Performance penalty for generality of SOAP document type support
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Model-Driven MVCS SOAP support
IOrderService:type-safe Service interface
OrderItemSummary.as
new ClassDescriptor("OrderItemSummary")
OrderService:Service Implementation
AddToCartOperation:Operation Implementation
SOAP Marshaller/Unmarshaller
Controller
SOAP/XML(follows document/literal
conventions only)
per-class metadata
drives XML parsing/
generation
populate value objectfrom response
invoke API to obtain operation
Order line item view
change eventscause data binding
update in view
executeoperation
create operation
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Model-Driven REST Support
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REST: accessing a data web
Each distinct entity is served from a stable URL
All relationships are represented as hyperlinks
A relationship may be: lazy (only a hyperlink in referent)
eager (target object details included in referent)
anywhere in between
Very suitable for read-only data
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REST data web
<Category uri="/cat/1" name="Widgets"> <products> <Product uri="/product/11" title="Cool Widget"/>
<Product uri="/product/12" title="Cooler Widget"/> </products></Category>
http://example.com/cat/1:
<Product uri="/product/11" title="Cool Widget" price="33.00"> <images> <Asset type="large" href="/images/11large.png"> <Asset type="small" href="/images/11small.png"> </images></Product>
http://example.com/product/11:
<Product uri="/product/11" title="Cooler Widget" price="66.00"> <images> <Asset type="large" href="/images/12large.png"> </images></Product>
http://example.com/product/12:
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ContentService:REST entity cache
Product.as
new ClassDescriptor("Product")
REST Unmarshaller
Controller
impl-dependentREST/XML
document format
per-class metadata
drives XML parsing/
generation
create/populateentity instances
request entity by URIon behalf of view
Product display view
change eventscause data bindingupdate in view
Model-Driven MVCS REST support
request formissing propertytriggers loading
populate objectsfrom XML responses
load entitieson demand
Category.as
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OzoneLayer:model-driven client/client
integration
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Conventional single-user outliner app
modifications
Flex Client
OutlineView
actionsdata,events
IOutlineController
OutlineController
Outline
IOutline
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Add OzoneLayer and stir: multiuser outliner
OutlineControllerProxy
Flex Client
OutlineView
actionsdata,events
IOutlineController
OutlineController
SharedScope
Flash Media Server(or moral equivalent)
Shared Object Services
Outline
IOutline
OutlineProxymod
ificati
on
s OutlineControllerProxy
Flex Client
OutlineView
actionsdata,events
IOutlineController
OutlineController
SharedScope Outline
IOutline
OutlineProxymod
ificati
on
s
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OzoneLayer: What Hamachi generates
OutlineControllerProxy
Flex Client
OutlineView
actionsdata,events
IOutlineController
OutlineController
SharedScope Outline
IOutline
OutlineProxymod
ificati
on
s OutlineControllerProxy
Flex Client
OutlineView
actionsdata,events
IOutlineController
OutlineController
SharedScope Outline
IOutline
OutlineProxymod
ificati
on
s
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Pros
+ One change in model expresses many in system
+ Eliminates many tedious, error-prone changes
+ Enabling technology for custom networking approaches
+ Change to module can affect the "way it works" with no distrubance to the model
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Cons
- Longer "curve to liftoff"
- More complex system, harder to learn
- Models, metamodels not fully standardized
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Some caveats
Approaches, not turnkey tools
Not all source code available yet
Limited documentation
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