Inversion Of Control: Spring.Net Overview

10 May, 2009
Inversion Of Control -
Spring.NETOverview

Dependencies and Dependency Injection
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Inversion Of Control - Spring.NET Overview

What is Dependency Injection?
Dependency injection (DI) in programming refers to the process of supplying an external dependency to a software component.
It is a specific form of inversion of control where the concern being inverted is the process of obtaining the needed dependency.
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But … what is Inversion of control?
Inversion of control, or IoC, is an abstract principle describing an aspect of some software architecture designs in which the flow of control of a system is inverted in comparison to the traditional architecture.
Control flow is expressed in imperative programming in the form of a series of instructions or procedure calls. Instead of specifying a sequence of decisions and procedures to occur during the lifetime of a process, the user of a IoCframework writes the desired responses linked to particular events or data requests.
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IOC Container
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Aha…and what is an IOC container?
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Spring.NET
an application framework for buidling Enterprise .NET applications
an IoC Container (Inversion of Control) that manages and injects dependencies on behalf of developers (DI = Dependency Injection)
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And more…
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IoC Containers for .NET
PicoContainer.NET: lightweight and highly embeddable IoC container
StructureMap: lightweight Inversion of Control (IoC) Container written in C#; can improve the architectural qualities of .NET apps by reducing the mechanical costs of good design techniques
Castle: Tools for application development including small IoC container
Spring.NET: full featured IoC container (port of Java version)
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Practice First approach - Dependencies
public class ExampleObject {
private AnotherObjectobjectOne; // dependencies
private YetAnotherObjectobjectTwo;
private inti;
public AnotherObjectObjectOne {
set { this.objectOne = value; }
}
public YetAnotherObjectObjectTwo {
set { this.objectTwo = value; }
}
public intIntegerProperty {
set { this.i = value; }
}
}
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Configuration I
Preferred way to create Object Factories and Application contexts is via configuration:
<configuration>
<configSections>
<sectionGroup name="spring">
<section name="context" type="Spring.Context.Support.ContextHandler, Spring.Core"/>
<section name="objects" type="Spring.Context.Support.DefaultSectionHandler, Spring.Core" />
</sectionGroup>
</configSections>
<spring>
<context>
<resource uri="config://spring/objects"/>
</context>
<objects>
...
</objects>
</spring>
</configuration>
Handlers usedfor Spring configurationsection
Where to find object configuration, e.g. file, assembly, config
Configurationof Spring managedobjects
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Configuration II
The configuration tells Spring.NET how objects depend on each other:
Object name
Object type: namespacepath + class, assembly
<object id="exampleObject" type="Examples.ExampleObject, ExamplesLibrary">
<property name="objectOne" ref="anotherExampleObject"/>
<property name="objectTwo" ref="yetAnotherObject"/>
<property name="IntegerProperty" value="1"/>
</object>
<object id="anotherExampleObject" type="Examples.AnotherObject, ExamplesLibrary"/>
<object id="yetAnotherObject" type="Examples.YetAnotherObject, ExamplesLibrary"/>
Properties referring to other objects: often called dependencies or collaborators
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Usage
Now instantiating an
ApplicationContext is simple:
ID that should appear in object configuration
IApplicationContextctx = ContextRegistry.GetContext();
ExampleObject person = (ExampleObject)ctx.GetObject(“exampleObject ");
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Example application
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Solve the dependencies with Spring.NET IOC
Demo
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http://en.wikipedia.org/wiki/Inversion_of_control
http://martinfowler.com/articles/injection.html
http://abdullin.com/wiki/inversion-of-control-ioc.html
http://www.springframework.net/doc-latest/reference/html/objects.html
http://www.developer.com/net/csharp/article.php/3722931/Dependency-Injection-with-SpringNet.htm
Resources

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10 May, 2009