Markus 5ce932ceb7 Work on #213
- properly categorize all patterns
- remove pattern list from readme
- minor fixes to readme
- removed "introduction" because its not a pattern and an error i
committed some time ago
2015-08-20 21:40:07 +02:00

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Markdown

---
layout: pattern
title: Dependency Injection
folder: dependency-injection
permalink: /patterns/dependency-injection/
categories: Behavioral
tags: Java
---
**Intent:** Dependency Injection is a software design pattern in which one or
more dependencies (or services) are injected, or passed by reference, into a
dependent object (or client) and are made part of the client's state. The
pattern separates the creation of a client's dependencies from its own
behavior, which allows program designs to be loosely coupled and to follow the
inversion of control and single responsibility principles.
![alt text](./etc/dependency-injection.png "Dependency Injection")
**Applicability:** Use the Dependency Injection pattern when
* when you need to remove knowledge of concrete implementation from object
* to enable unit testing of classes in isolation using mock objects or stubs