Introduce Update annotation.

Switch update execution to an annotation based model that allows usage of both the classic update as well as the aggregation pipeline variant. Add the reactive variant of it.
Make sure to allow parameter binding for update expressions and verify method return types.
Update Javadoc and reference documentation.

See: #2107
Original Pull Request: #284

src/main/asciidoc/new-features.adoc

@@ -1,6 +1,11 @@
 [[new-features]]
 = New & Noteworthy
 
+[[new-features.3.4]]
+== What's New in Spring Data MongoDB 3.4
+
+* Find and update ``Document``s via <<mongodb.repositories.queries.update,Repository method>>.
+
 [[new-features.3.3]]
 == What's New in Spring Data MongoDB 3.3
 

src/main/asciidoc/reference/mongo-repositories.adoc

@@ -289,6 +289,56 @@ lower / upper bounds (`$gt` / `$gte` & `$lt` / `$lte`) according to `Range`
 
 NOTE: If the property criterion compares a document, the order of the fields and exact equality in the document matters.
 
+[[mongodb.repositories.queries.update]]
+=== Repository Update Methods
+
+The keywords in the preceding table can also be used to create queries that identify matching documents for running updates on them.
+The actual update action is defined via the `@Update` annotation on the method itself as shown in the snippet below. +
+Please note that the naming schema for derived queries starts with `find`.
+Using _update_ (as in `updateAllByLastname(...)`) is only allowed in combination with `@Query`.
+
+The update is applied to *all* matching documents and it is *not* possible to limit the scope by passing in a `Page` nor using any of the <<repositories.limit-query-result,limiting keywords>>. +
+The return type can be either `void` or a _numeric_ type, such as `long` which holds the number of modified documents.
+
+.Update Methods
+====
+[source,java]
+----
+public interface PersonRepository extends CrudRepository<Person, String> {
+
+  @Update("{ '$inc' : { 'visits' : 1 } }")
+  long findAndIncrementVisitsByLastname(String lastname); <1>
+
+  @Update("{ '$inc' : { 'visits' : ?1 } }")
+  void findAndIncrementVisitsByLastname(String lastname, int increment); <2>
+
+  @Update("{ '$inc' : { 'visits' : ?#{[1]} } }")
+  long findAndIncrementVisitsUsingSpELByLastname(String lastname, int increment); <3>
+
+  @Update(pipeline = {"{ '$set' : { 'visits' : { '$add' : [ '$visits', ?1 ] } } }"})
+  void findAndIncrementVisitsViaPipelineByLastname(String lastname, int increment); <4>
+
+  @Update("{ '$push' : { 'shippingAddresses' : ?1 } }")
+  long findAndPushShippingAddressByEmail(String email, Address address); <5>
+
+  @Query("{ 'lastname' : ?0 }")
+  @Update("{ '$inc' : { 'visits' : ?1 } }")
+  void updateAllByLastname(String lastname, int increment); <6>
+}
+----
+<1> The filter query for the update is derived from the method name. The update is as is and does not bind any parameters.
+<2> The actual increment value is defined by the _increment_ method argument that is bound to the `?1` placeholder.
+<3> It is possible to use SpEL for parameter binding.
+<4> Use the `pipeline` attribute to issue <<mongo-template.aggregation-update,aggregation pipeline updates>>.
+<5> The update may contain complex objects.
+<6> Combine a <<mongodb.repositories.queries.json-based,string based query>> with an update.
+====
+
+[WARNING]
+====
+Repository updates do not emit persistence nor mapping lifecycle events.
+====
+
 [[mongodb.repositories.queries.delete]]
 === Repository Delete Queries