DATAMONGO-792 - Add support to configure auditing via JavaConfig.

Introduces the necessary infrastructure in form of MongoAuditingRegistrar to configure auditing with MongoDB via Annotation config. The MongoDB auditing feature can be enabled by annotating a configuration class with the EnableMongoAuditing annotation. Added section to reference documentation.

Original pull request: #94.

src/docbkx/reference/mongodb.xml

@@ -571,6 +571,66 @@ public class MongoConfiguration {
     </section>
   </section>
 
+  <section id="mongo.auditing">
+    <title>General auditing configuration</title>
+
+    <para>Activating auditing functionality is just a matter of adding the
+    Spring Data Mongo <literal>auditing</literal> namespace element to your
+    configuration:</para>
+
+    <example>
+      <title>Activating auditing in the Spring configuration</title>
+
+      <programlisting language="xml">&lt;mongo:auditing mapping-context-ref="customMappingContext" auditor-aware-ref="yourAuditorAwareImpl"/&gt;</programlisting>
+    </example>
+
+    <example>
+      <title>Auditing via Java Config</title>
+
+      <para>Since Spring Data MongoDB 1.4 Auditing can be enabled by
+      annotating a configuration class with the
+      <classname>EnableMongoAuditing</classname> annotation.</para>
+
+      <programlisting language="java">@Configuration
+@EnableMongoAuditing(auditorAwareRef="myAuditorProvider")
+@EnableMongoRepositories
+class Config {
+
+    @Bean
+    public AuditorAware&lt;AuditableUser&gt; myAuditorProvider() {
+        return new AuditorAwareImpl();
+    }
+}</programlisting>
+
+      <para>Note that if you want to record information about the create-User
+      or modify-User, you can delcare a bean that implements the
+      <classname>AuditorAware</classname> interface. The bean name can also be
+      configured explicitly via the <code>auditorAwareRef</code> attribute of
+      the <classname>EnableMongoAuditing</classname> annotation, this can be
+      used to resolve an ambiguity. If no <code>auditorAwareRef</code> is
+      specified explicitly we try to discover and autowire an
+      <classname>AuditorAware</classname> implementation.</para>
+    </example>
+
+    <para>As you can see you have to provide a bean that implements the
+    <interfacename>AuditorAware</interfacename> interface which looks as
+    follows:</para>
+
+    <example>
+      <title><interfacename>AuditorAware</interfacename> interface</title>
+
+      <programlisting language="java">public interface AuditorAware&lt;T, ID extends Serializable&gt; {
+
+    T getCurrentAuditor();
+}</programlisting>
+    </example>
+
+    <para>Usually you will have some kind of authentication component in your
+    application that tracks the user currently working with the system. This
+    component should be <interfacename>AuditorAware</interfacename> and thus
+    allow seamless tracking of the auditor.</para>
+  </section>
+
   <section id="mongo-template">
     <title>Introduction to MongoTemplate</title>
 
@@ -2465,8 +2525,8 @@ project("a","b").and("foo").as("bar") // will generate {$project: {a: 1, b: 1, b
 
         <para>In this introductory example we want to aggregate a list of tags
         to get the occurence count of a particular tag from a MongoDB
-        collection called <code>"tags"</code> sorted by the occurrence count in
-        descending order. This example demonstrates the usage of grouping,
+        collection called <code>"tags"</code> sorted by the occurrence count
+        in descending order. This example demonstrates the usage of grouping,
         sorting, projections (selection) and unwinding (result
         splitting).</para>