Dependency injection& comparative study
- 1. 1 GLOBALLOGIC Dependency Injection& Comparative study of different containers Pallav.Kumar 10/16/2014
- 2. 2 Inversion of Control It is a programming technique in which the object coupling is bound at runtime by a container and is not known at compile. In lay-man terms it is the capability of a consumer to consume a component without knowing in advance the specifics/origins of the consumed component. IOC can be achieved by Dependency injection or Service locator. Dependency is just another object your class needs to function. E.g. Model class has dependency on db object. Dependency injection means dependency is pushed inside a class from outside. You should not be instantiating the dependencies using new operator inside a class, instead take it as a constructor parameter or a setter. It is different from factory class, as the factory class knows about the consumed class breaks this abstraction and the plug and play feature. When to use dependency injection? Very effective at assembling loosely coupled components, and at configuring these components. Ability to specify component dependencies at run time. Simplified management of cross-cutting concerns. Increased testability of individual components. Need for pluggable architecture.
- 3. 3 Implementing Dependency Injection DI is a way of implementing IOC. In DI we have four broader ways of implementing the same: Constructor Injection: Dependencies are injected through the class constructor. Pass object reference in constructor itself. When the client creates the object he passes the object in the constructor while the object is created. Not suited for client who can only use default constructors. Property Injection: Dependent Object exposes a “Setter” method to inject the dependency. Mostly used. Dependent objects are exposed through set/get methods of classes. The bad point is because the objects are publicly exposed it breaks the encapsulation rule of object oriented programming. Interface Injection: The Service provides an interface which consumers must implement. The interface exposes specific behaviours at runtime. Implement an interface from the IOC framework. IOC framework will use the interface method to inject the object in the main class.
- 4. 4 Why to use It decouples your class construction from construction of its dependencies. Dependency Inversion Principle Code should depend on abstraction. By depending on abstraction we are decoupling our implementation from each other. High level modules should not depend on low level module. Both should depend on abstraction. Code should depend on interface that way we substitute different dependencies, we decouple our code from lower level implementation. We get modular, cleaner, easy to modify and readable code. Dependency Injection Pros & Cons Pros Loosely Coupled & Highly Cohesive. Increased Testability & Maintainability. Flexibility of run time configuration. Inversions of Control containers do the wiring for you. Cons Increased code complexity. Can complicate debugging during the learning curve. Code flow becomes non-trivial. For class we need to figure out what are its dependencies and how to instantiate the dependencies. Dependency injection container It is a map of dependencies that your class needs with logic to create those dependencies if they have not created yet. Every time you ask for a dependency, the map will figure out which dependency to use, the container will check to see if it has created one of those dependencies already, it has it will return that otherwise it will create dependency, store it and return it.
- 5. 5 Instead of creating classes yourself you ask for container for new instance. Container can resolve complex dependencies transparently. If you need to swap out generic dependency, you need to update the container. Dependency injection Containers Benchmark - Performance comparison Performance Configuration Features Environment Container Code XML Auto Auto wiring Custom lifetimes Interception Auto diagnostics .NET SL WP7 WP8 WinRT AutoFac Average Yes Yes Yes Yes No Yes No Yes Yes Yes Yes Yes Caliburn.Micro Average Yes No No Yes No No No Yes Yes Yes Yes Yes Catel Average Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes DryIoc Fast Yes No No Yes Yes No No Yes No No No No Dynamo Fast Yes No Yes Yes Yes No No Yes No No No No fFastInjector Fast Yes No No Yes No No No Yes Yes Yes No Yes HaveBox Fast Yes No No Yes No Yes No Yes Yes Yes Yes No Hiro Fast Yes No No Yes No No No Yes No No No No IfInjector Fast Yes No No Yes No No No Yes Yes Yes No Yes LightCore Average Yes Yes Yes Yes Yes No No Yes Yes No No No LightInject Fast Yes No Yes Yes Yes Yes No Yes Yes No Yes Yes Maestro Average Yes No No Yes Yes Yes No Yes Yes Yes Yes Yes MEF Slow Yes No No Yes No No No Yes Yes No No Yes
- 6. 6 MEF2 Fast Yes No No Yes No No No Yes No Yes Yes Yes Ninject Slow Yes Yes Yes Yes Yes No No Yes Yes Yes No Yes Petite Fast Yes No No No No No No Yes No No No No SimpleInjector Fast Yes No Yes Yes Yes Yes Yes Yes Yes No Yes Yes Speedioc Fast Yes No No No No No No Yes No No No No Spring.NET Very slow No Yes No Yes No Yes No Yes No No No No Stiletto Average Yes No No Yes No No No Yes Yes Yes Yes No StructureMap Average Yes Yes Yes Yes Yes Yes Yes Yes No Yes No Yes StyleMVVM Fast Yes No Yes Yes Yes No No Yes No No Yes No TinyIoc Average Yes No No Yes Yes No No Yes Yes Yes No No Unity Average Yes Yes Yes Yes Yes Yes No Yes Yes No Yes Yes Windsor Average Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No Ninject is definitely the slowest container. MEF and Spring.NET are faster than Ninject, but still pretty slow. AutoFac, Catel and Windsor come next, followed by StructureMap, Unity and LightCore. A disadvantage of Spring.NET is, that can only be configured with XML. DryIoc, LightInject and SimpleInjector offer a very performance combined with support for advanced scenarios like interception and generic decorators. Simple Injector and LightInject also provide extensive documentation and support all important platforms.