DATACOUCH-168 - Support and document all reduce functions

Detection whether or not reduce should be activated is now centralized. Triggers are:
  - using the count prefix instead of find in method name
  - setting reduce = true in the View annotation explicitly.

The reduce can thus be returning any kind of value (added an integration example with _stats), which is now properly documented.

src/integration/java/org/springframework/data/couchbase/repository/CouchbaseRepositoryViewListener.java

@@ -56,9 +56,11 @@ public class CouchbaseRepositoryViewListener extends DependencyInjectionTestExec
   private void createAndWaitForDesignDocs(final Bucket client) {
     String mapFunction = "function (doc, meta) { if(doc._class == \"org.springframework.data.couchbase.repository.User\") { emit(null, null); } }";
     String mapFunctionName = "function (doc, meta) { if(doc._class == \"org.springframework.data.couchbase.repository.User\") { emit(doc.username, null); } }";
+    String mapFunctionAge = "function (doc, meta) { if(doc._class == \"org.springframework.data.couchbase.repository.User\") { emit(doc.age, doc.age); } }";
     View view = DefaultView.create("customFindAllView", mapFunction, "_count");
     View customFindByNameView = DefaultView.create("customFindByNameView", mapFunctionName, "_count");
-    List<View> views = Arrays.asList(view, customFindByNameView);
+    View customFindByAgeStatsView = DefaultView.create("customFindByAgeStatsView", mapFunctionAge, "_stats");
+    List<View> views = Arrays.asList(view, customFindByNameView, customFindByAgeStatsView);
     DesignDocument designDoc = DesignDocument.create("user", views);
     client.bucketManager().upsertDesignDocument(designDoc);
 

src/integration/java/org/springframework/data/couchbase/repository/CouchbaseRepositoryViewTests.java

@@ -25,6 +25,7 @@ import java.util.Arrays;
 import java.util.List;
 
 import com.couchbase.client.java.Bucket;
+import com.couchbase.client.java.document.json.JsonObject;
 import com.couchbase.client.java.view.Stale;
 import com.couchbase.client.java.view.ViewQuery;
 import com.couchbase.client.java.view.ViewResult;
@@ -111,6 +112,17 @@ public class CouchbaseRepositoryViewTests {
     assertEquals(12, count);
   }
 
+  @Test
+  public void shouldDeriveViewParametersAndReduceNonNumerical() {
+    JsonObject reduceResult = repository.findByAgeLessThan(50);
+
+    assertNotNull(reduceResult);
+    assertEquals(51, (long) reduceResult.getLong("count"));
+    assertEquals(50, (long) reduceResult.getLong("max"));
+    assertEquals(0, (long) reduceResult.getLong("min"));
+    assertEquals(1275, (long) reduceResult.getLong("sum"));
+  }
+
   @Test
   public void shouldDeriveViewParameters() {
     String lowKey = "uname-1";

src/integration/java/org/springframework/data/couchbase/repository/CustomUserRepository.java

@@ -18,6 +18,8 @@ package org.springframework.data.couchbase.repository;
 
 import java.util.List;
 
+import com.couchbase.client.java.document.json.JsonObject;
+
 import org.springframework.data.couchbase.core.view.View;
 
 /**
@@ -72,4 +74,7 @@ public interface CustomUserRepository extends CouchbaseRepository<User, String>
 
   @View
   long countCustomFindInvalid();
+
+  @View(viewName = "customFindByAgeStatsView", reduce = true)
+  JsonObject findByAgeLessThan(int maxAge);
 }