Adds basic Spring Data Envers specific documentation.

Closes #61
See spring-projects/spring-data-examples#603

src/main/asciidoc/envers.adoc

@@ -0,0 +1,134 @@
+[[envers.what]]
+== What is Spring Data Envers
+
+Spring Data Envers differs from other Spring Data modules in that it is always used in combination with another Spring Data Module: Spring Data JPA.
+It makes typical Envers queries available in repositories for Spring Data JPA.
+
+== What is Envers?
+
+Envers is a Hibernate module which adds auditing capabilities to JPA entities.
+This documentation assumes you are familiar with Envers just as Spring Data Envers relies on Envers being properly configured.
+
+
+[[envers.getting-started]]
+== Getting Started
+
+As a starting point for using Spring Data Envers you need a project with Spring Data JPA.
+The easiest way to create that is using the Spring Initializr either on start.spring.io or via its integration in your favorite IDE.
+
+Now add spring-data-envers as a dependency
+[source,xml,subs="+attributes"]
+----
+<dependencies>
+
+  <!-- other dependency elements omitted -->
+
+  <dependency>
+    <groupId>org.springframework.data</groupId>
+    <artifactId>spring-data-envers</artifactId>
+    <version>{version}</version>
+  </dependency>
+
+</dependencies>
+----
+This will also bring hibernate-envers into the project as a transient dependency.
+
+Next is to make one or more repositories into {spring-data-commons-javadoc-base}/org/springframework/data/repository/history/RevisionRepository.html[`RevisionRepository`] by adding it as an extended interface.
+
+[source,java]
+----
+public interface PersonRepository
+    extends CrudRepository<Person, Long>,
+    RevisionRepository<Person, Long, Long> {}
+----
+
+In order to provide an implementations contained in that interface we have to use a different `repositoryFactoryBeanClass` for creating repositories.
+
+[source,java]
+----
+@SpringBootApplication
+@EnableJpaRepositories(repositoryFactoryBeanClass = EnversRevisionRepositoryFactoryBean.class)
+public class EnversDemoConfiguration {}
+----
+
+The entity for that repository should be an entity with Envers auditing enabled, i.e. it has an `@Audited` annotation.
+
+[source,java]
+----
+@Entity
+@Audited
+public class Person {
+
+	@Id @GeneratedValue
+	Long id;
+	String name;
+	@Version Long version;
+}
+----
+
+You may now use the methods from `RevisionRepository` to query the revisions of the entity as demonstrated in the following test case.
+
+
+
+[source,java]
+----
+@ExtendWith(SpringExtension.class)
+@SpringBootTest
+public class EnversIntegrationTests {
+
+	@Autowired PersonRepository repository;
+	@Autowired TransactionTemplate tx;
+
+	@Test
+	void testRepository() {
+
+		Person updated = preparePersonHistory();
+
+		Revisions<Long, Person> revisions = repository.findRevisions(updated.id);
+
+		assertThat(revisions) //
+				.extracting( //
+						rev -> rev.getEntity().name, //
+						rev -> rev.getMetadata().getRevisionType()) //
+				.containsExactly( //
+						tuple("John", RevisionType.INSERT), //
+						tuple("Jonny", RevisionType.UPDATE), //
+						tuple(null, RevisionType.DELETE) //
+				);
+	}
+
+	private Person preparePersonHistory() {
+
+		Person john = new Person();
+		john.setName("John");
+
+		//create
+		Person saved = tx.execute(__ -> repository.save(john));
+		assertThat(saved).isNotNull();
+
+		saved.setName("Jonny");
+
+		// update
+		Person updated = tx.execute(__ -> repository.save(saved));
+		assertThat(updated).isNotNull();
+
+		// delete
+		tx.executeWithoutResult(__->repository.delete(updated));
+		return updated;
+	}
+}
+----
+
+
+[[envers.resources]]
+== Further Resources
+
+There is a https://github.com/spring-projects/spring-data-examples[Spring Data Envers example in the Spring Data Examples repository] that you can download and play around with to get a feel for how the library works.
+
+You should also check out the https://docs.spring.io/spring-data/commons/docs/current/api/org/springframework/data/repository/history/RevisionRepository.html[Javadoc for `RevisionRepository`] and related classes.
+
+Questions are best asked at https://stackoverflow.com/questions/tagged/spring-data-envers[Stackoverflow using the `spring-data-envers` tag].
+
+The https://github.com/spring-projects/spring-data-envers[source code and issue tracker for Spring Data Envers is hosted at GitHub].
+
+

src/main/asciidoc/index.adoc

@@ -1,9 +1,10 @@
 = Spring Data Envers - Reference Documentation
-Oliver Gierke;
+Oliver Gierke; Jens Schauder
 :revnumber: {version}
 :revdate: {localdate}
+:javadoc-base: https://docs.spring.io/spring-data/envers/docs/{revnumber}/api/
 :spring-data-commons-docs: ../../../../spring-data-commons/src/main/asciidoc
-
+:spring-data-commons-javadoc-base: https://docs.spring.io/spring-data/commons/docs/current/api/
 (C) 2008-2021 The original authors.
 
 NOTE: Copies of this document may be made for your own use and for distribution to others, provided that you do not charge any fee for such copies and further provided that each copy contains this Copyright Notice, whether distributed in print or electronically.
@@ -14,13 +15,13 @@ include::{spring-data-commons-docs}/dependencies.adoc[leveloffset=+1]
 include::{spring-data-commons-docs}/repositories.adoc[leveloffset=+1]
 
 [[reference]]
-= Reference Documentation
+== Reference Documentation
 
-== TODO
+include::envers.adoc[leveloffset=+1]
 
 
 [[appendix]]
-= Appendix
+== Appendix
 
 :numbered!:
 include::{spring-data-commons-docs}/repository-namespace-reference.adoc[leveloffset=+1]