all index.md files renamed to README.md for more compatibility with github

service-layer/README.md

@@ -0,0 +1,31 @@
+---
+layout: pattern
+title: Service Layer
+folder: service-layer
+permalink: /patterns/service-layer/
+categories: Architectural
+tags:
+ - Java
+ - Difficulty-Intermediate
+---
+
+## Intent
+Service Layer is an abstraction over domain logic. Typically
+applications require multiple kinds of interfaces to the data they store and
+logic they implement: data loaders, user interfaces, integration gateways, and
+others. Despite their different purposes, these interfaces often need common
+interactions with the application to access and manipulate its data and invoke
+its business logic. The Service Layer fulfills this role.
+
+![alt text](./etc/service-layer.png "Service Layer")
+
+## Applicability
+Use the Service Layer pattern when
+
+* you want to encapsulate domain logic under API
+* you need to implement multiple interfaces with common logic and data
+
+## Credits
+
+* [Martin Fowler - Service Layer](http://martinfowler.com/eaaCatalog/serviceLayer.html)
+* [Patterns of Enterprise Application Architecture](http://www.amazon.com/Patterns-Enterprise-Application-Architecture-Martin/dp/0321127420)