DATACOUCH-59 - Allow expiry touch on read

Configuration is based on Document annotation. When read of document takes place then touch action is executed on document. It is an asynchronous action so it does not block read. It is executed only on single reads (not view-based or N1QL-based ones).

src/main/java/org/springframework/data/couchbase/core/CouchbaseTemplate.java

@@ -281,10 +281,15 @@ public class CouchbaseTemplate implements CouchbaseOperations, ApplicationEventP
 
   @Override
   public <T> T findById(final String id, Class<T> entityClass) {
+    final CouchbasePersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
     RawJsonDocument result = execute(new BucketCallback<RawJsonDocument>() {
       @Override
       public RawJsonDocument doInBucket() {
-        return client.get(id, RawJsonDocument.class);
+        if (entity.isTouchOnRead()) {
+          return client.getAndTouch(id, entity.getExpiry(), RawJsonDocument.class);
+        } else {
+          return client.get(id, RawJsonDocument.class);
+        }
       }
     });
 

src/main/java/org/springframework/data/couchbase/core/mapping/BasicCouchbasePersistentEntity.java

@@ -16,12 +16,7 @@
 
 package org.springframework.data.couchbase.core.mapping;
 
-import java.util.Calendar;
-import java.util.TimeZone;
-import java.util.concurrent.TimeUnit;
-
 import com.couchbase.client.java.repository.annotation.Id;
-
 import org.springframework.beans.BeansException;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
@@ -31,6 +26,10 @@ import org.springframework.data.mapping.model.BasicPersistentEntity;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
 
+import java.util.Calendar;
+import java.util.TimeZone;
+import java.util.concurrent.TimeUnit;
+
 /**
  * The representation of a persistent entity.
  *
@@ -123,4 +122,11 @@ public class BasicCouchbasePersistentEntity<T> extends BasicPersistentEntity<T,
     }
   }
 
+  @Override
+  public boolean isTouchOnRead() {
+    org.springframework.data.couchbase.core.mapping.Document annotation = getType().getAnnotation(
+        org.springframework.data.couchbase.core.mapping.Document.class);
+    return annotation == null ? false : getExpiry() > 0 && annotation.touchOnRead();
+  }
+
 }

src/main/java/org/springframework/data/couchbase/core/mapping/CouchbasePersistentEntity.java

@@ -42,4 +42,12 @@ public interface CouchbasePersistentEntity<T> extends
    */
   int getExpiry();
 
+  /**
+   * Flag for using getAndTouch operations for reads, resetting the expiration (if one was set) when the
+   * entity is directly read (eg. findOne, findById).
+   *
+   * @return true if a direct read of the document should trigger a touch, resetting its expiration timer.
+   */
+   boolean isTouchOnRead();
+
 }

src/main/java/org/springframework/data/couchbase/core/mapping/Document.java

@@ -46,4 +46,10 @@ public @interface Document {
    */
   TimeUnit expiryUnit() default TimeUnit.SECONDS;
 
+  /**
+   * An optional flag associated with {@link #expiry()} indicating whether the expiry timer should
+   * be reset whenever the document is directly read (eg. findByOne, findById).
+   */
+  boolean touchOnRead() default false;
+
 }