Added molgenis-data-jpa documentation

molgenis-data-jpa/doc/molgenis-data-jpa.md

@@ -0,0 +1,67 @@
+## Introduction
+The molgenis-data-jpa package is an jpa data backend for Molgenis. All entities descibed in the Molgenis dsl model xml files and that are generated using the Molgenis generator can be used with the Data Api. It provides functionality to query, create, update and delete jpa entities.
+
+For this package to work you must configure your spring applicationcontext for use with jpa. You can do this by including the `org.molgenis.DatabaseConfig` spring configuration class.
+
+## Core molgenis-data-jpa classes
+<img src="molgenis-data-jpa.png" /> 
+
+**The light grey classes are provided by the core molgenis-data module**
+
+**The classes marked 'generated' will be generated by the Molgenis generator**
+
+### JpaEntity
+The JpaEntity interface is implemented by all jpa entities. The concrete jpa entities are generated by the Molgenis generater according to the domain specific xml configuration files. The entities are strongly typed but they also implement the `Entity` interface so you can them like any other entity implementation.
+
+The entities contain a field named `ENTITY_NAME` that contains the name of the entity.
+Alsp for all fieldnames constants are generated.
+
+### JpaRepository
+For all jpa entities defined in the configuration file a jpa repository is generated that is derived from the `AbstractJpaRepository`. It is a wrapper around the `javax.persistence.EntityManager`. For every jpa entity there is a strongly type jpa repository. 
+
+The required metadata classes are also generated.
+
+### JpaEntitySourceImpl
+This is generated to contain all jpa repositories. One exists per application. The url is always `jpa://`.
+
+### JpaEntitySourceFactory
+Just returns the generated `JpaEntitySourceImpl` as there can be only one JpaEntitySource per application.
+The url prefix is `jpa://`.
+
+### JpaEntitySourceRegistrator
+This class will registers the jpa entity source if it is in your spring context. It is annotated with `@Component` so when you have this class inculded in your spring component scan, everything will be automatically registered (example `@ComponentScan("org.molgenis")`).
+
+## Usage example
+
+*** Model ***
+
+```
+<?xml version="1.0" encoding="UTF-8"?>
+<molgenis name="org.molgenis">
+	<module name="test">
+		<entity name="Person">
+			<field name="id" type="autoid" />
+			<field name="name" type="string" />
+		</entity>
+	</module>
+</molgenis>
+```
+
+*** Find a Person with name 'Piet' ***
+
+```
+DataService dataService = ...;
+Query q = new QueryImpl().eq(Person.NAME, "Piet");
+Person person = dataService.findOne(Person.ENTITY_NAME, q);
+```
+
+
+
+
+
+
+
+
+
+
+