Build projection support for cached entities

src/main/java/com/universeprojects/cacheddatastore/CachedDatastoreService.java

@@ -26,6 +26,7 @@
 import com.google.appengine.api.datastore.KeyFactory;
 import com.google.appengine.api.datastore.KeyRange;
 import com.google.appengine.api.datastore.PreparedQuery;
+import com.google.appengine.api.datastore.PropertyProjection;
 import com.google.appengine.api.datastore.Query;
 import com.google.appengine.api.datastore.Query.Filter;
 import com.google.appengine.api.datastore.QueryResultList;
@@ -589,7 +590,16 @@ public void putIfChanged(Collection<CachedEntity> entities)
 	}
 
 	public void put(Collection<CachedEntity> entities)
-	{
+	{		
+		entities.removeIf(entity -> {
+			if(entity.projected) {
+				log.log(Level.WARNING, "Attempted to save a projected entity with key " + entity.getKey().toString());
+				return true;
+			}
+			else return false;
+		});
+
+
 		if (bulkPutMode)
 		{
 			entitiesToBulkPut.removeAll(entities);
@@ -653,6 +663,10 @@ public void put(Collection<CachedEntity> entities)
 
 	public void put(CachedEntity entity)
 	{
+		if(entity.projected) {
+			log.log(Level.WARNING, "Attempted to save a projected entity with key " + entity.getKey().toString());
+			return;
+		}
 		if (bulkPutMode)
 		{
 			entitiesToBulkPut.remove(entity);
@@ -1187,8 +1201,31 @@ else if (dbEntity!=null)
 		return result;
 	}
 
-
-
+	/**
+	 * This method returns partial entities.
+	 * @param limit
+	 * @param q
+	 * @param projections 
+	 * @return
+	 */
+	public List<CachedEntity> fetchProjectedList(int limit, Query q, Set<String> projections){
+
+		for(String proj : projections) {
+			q.addProjection(new PropertyProjection(proj, null));
+		}
+
+		prepareQuery(q);
+
+		FetchOptions fo = FetchOptions.Builder.withLimit(limit).chunkSize(limit).prefetchSize(limit);
+
+		List<Entity> entities = pq.asList(fo);
+		List<CachedEntity> result = new ArrayList<>();
+
+
+		entities.forEach(n -> result.add(CachedEntity.wrap(n, true)));
+
+		return result;
+	}
 
 
 	public CachedEntity fetchSingleEntity(Query q)

src/main/java/com/universeprojects/cacheddatastore/CachedEntity.java

@@ -1,29 +1,36 @@
 package com.universeprojects.cacheddatastore;
 
 import java.io.Serializable;
+import java.util.Collection;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.logging.Logger;
 
 import com.google.appengine.api.datastore.Entity;
 import com.google.appengine.api.datastore.EntityNotFoundException;
 import com.google.appengine.api.datastore.Key;
 import com.google.appengine.api.datastore.KeyFactory;
+import com.google.appengine.api.datastore.RawValue;
 import com.google.appengine.api.datastore.Text;
 
 public class CachedEntity implements Cloneable,Serializable {
 	private static Logger log = Logger.getLogger(CachedEntity.class.toString());
 
-
 	private transient Map<String,Object> attributes;
 
 	private static final long serialVersionUID = 3034412029610092898L;
+
 	protected Entity entity;
 	boolean unsavedChanges = false;
 	boolean deleted = false;
 	boolean newEntity = false;
 
+	public final boolean projected;
+	private Set<String> projections;
+
 	public CachedEntity(Key key)
 	{
 		this(new Entity(key));
@@ -89,11 +96,14 @@ public CachedEntity(String kind, String keyName, Key parent)
 		unsavedChanges = true;
 	}
 
-
-
 	private CachedEntity(Entity entity) {
+		this(entity, false);
+	}
+
+	private CachedEntity(Entity entity, boolean projected) {
 		this.entity = entity;
 		newEntity = false;
+		this.projected = projected;
 	}
 
 	public boolean isDeleted()
@@ -132,6 +142,18 @@ public void refetch(CachedDatastoreService ds)
 			throw new IllegalStateException("Unable to refetch. Entity "+getKey()+" was deleted.");
 		}
 	}
+
+	public void setProjections(Collection<String> newProjections) {
+		if(projected == false || projections != null)
+			return;
+
+		projections = new HashSet<>();
+		newProjections.forEach(n -> projections.add(n));
+	}
+
+	public Set<String> getProjections(){
+		return projections;
+	}
 
 	public CachedEntity clone()
 	{
@@ -260,10 +282,22 @@ public Map<String, Object> getProperties()
 
 	public Object getProperty(String propertyName)
 	{
-		if (entity.getProperty(propertyName) instanceof Text)
-			return ((Text)entity.getProperty(propertyName)).getValue();
-		else
-			return entity.getProperty(propertyName);
+
+		Object result = null;
+
+		if(projected && projections != null && projections.contains(propertyName) == false) 
+			return result;
+
+		result = entity.getProperty(propertyName);
+
+		if(result instanceof RawValue) 
+			result = ((RawValue) result).getValue();
+
+		if(result instanceof Text) 
+			result = ((Text) result).getValue();
+
+
+		return result;
 	}
 
 	public boolean hasProperty(String propertyName)
@@ -309,11 +343,15 @@ public void setProperty(String propertyName, Object value)
 		unsavedChanges = true;
 	}
 
-	public static CachedEntity wrap(Entity obj)
-	{
+	public static CachedEntity wrap(Entity obj, boolean projected) {
 		if (obj==null) return null;
 		return new CachedEntity(obj);
 	}
+
+	public static CachedEntity wrap(Entity obj)
+	{
+		return wrap(obj, false);
+	}
 
 	public void setPropertyManually(String propertyName, Object value)
 	{

src/main/java/com/universeprojects/cacheddatastore/QueryHelper.java

@@ -1,11 +1,11 @@
 package com.universeprojects.cacheddatastore;
 
 import java.util.List;
+import java.util.Set;
 
 import com.google.appengine.api.datastore.Cursor;
 import com.google.appengine.api.datastore.Key;
 import com.google.appengine.api.datastore.Query;
-import com.google.appengine.api.datastore.Query.CompositeFilter;
 import com.google.appengine.api.datastore.Query.CompositeFilterOperator;
 import com.google.appengine.api.datastore.Query.Filter;
 import com.google.appengine.api.datastore.Query.FilterOperator;
@@ -280,7 +280,40 @@ public List<CachedEntity> getFilteredORList(Cursor cursor, String kind, String f
 		q.setFilter(filter);
 
 		return ds.fetchAsList(q, 1000, cursor);
-	}	
+	}
+
+	public List<CachedEntity> getProjectedList(Set<String> projections, String kind, int limit, String name, FilterOperator operator, Object value){
+
+		FilterPredicate f1 = new FilterPredicate(name, operator, value);
+		Query q = new Query(kind);
+		q.setFilter(f1);				
+
+		return ds.fetchProjectedList(limit, q, projections);
+	}
+
+	public List<CachedEntity> getProjectedList(Set<String> projections, String kind, int limit, String name, FilterOperator operator, Object value,
+			String name2, FilterOperator operator2, Object value2){
+
+		FilterPredicate f1 = new FilterPredicate(name, operator, value);
+		FilterPredicate f2 = new FilterPredicate(name2, operator2, value2);
+		Query q = new Query(kind);
+		q.setFilter(CompositeFilterOperator.and(f1, f2));				
+
+		return ds.fetchProjectedList(limit, q, projections);
+	}
+
+	public List<CachedEntity> getProjectedList(Set<String> projections, String kind, int limit, String name, FilterOperator operator, Object value,
+			String name2, FilterOperator operator2, Object value2,
+			String name3, FilterOperator operator3, Object value3){
+
+		FilterPredicate f1 = new FilterPredicate(name, operator, value);
+		FilterPredicate f2 = new FilterPredicate(name2, operator2, value2);
+		FilterPredicate f3 = new FilterPredicate(name3, operator3, value3);
+		Query q = new Query(kind);
+		q.setFilter(CompositeFilterOperator.and(f1, f2, f3));				
+
+		return ds.fetchProjectedList(limit, q, projections);
+	}
 
 	/**
 	 * This performs an ancestor query to fetch all children (within a limit)