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

repository/README.md

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+---
+layout: pattern
+title: Repository
+folder: repository
+permalink: /patterns/repository/
+categories: Persistence Tier
+tags:
+ - Java
+ - Difficulty-Intermediate
+ - Spring
+---
+
+## Intent
+Repository layer is added between the domain and data mapping
+layers to isolate domain objects from details of the database access code and
+to minimize scattering and duplication of query code. The Repository pattern is
+especially useful in systems where number of domain classes is large or heavy
+querying is utilized.
+
+![alt text](./etc/repository.png "Repository")
+
+## Applicability
+Use the Repository pattern when
+
+* the number of domain objects is large
+* you want to avoid duplication of query code
+* you want to keep the database querying code in single place
+* you have multiple data sources
+
+## Real world examples
+
+* [Spring Data](http://projects.spring.io/spring-data/)
+
+## Credits
+
+* [Don’t use DAO, use Repository](http://thinkinginobjects.com/2012/08/26/dont-use-dao-use-repository/)
+* [Advanced Spring Data JPA - Specifications and Querydsl](https://spring.io/blog/2011/04/26/advanced-spring-data-jpa-specifications-and-querydsl/)