OPENJPA-1473: Replace null object with non-null default for aggregate expressions

git-svn-id: https://svn.apache.org/repos/asf/openjpa/trunk@901454 13f79535-47bb-0310-9956-ffa450edef68

openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/kernel/exps/UnaryOp.java

@@ -113,8 +113,12 @@ abstract class UnaryOp
 
     public Object load(ExpContext ctx, ExpState state, Result res)
         throws SQLException {
-        return Filters.convert(res.getObject(this,
-            JavaSQLTypes.JDBC_DEFAULT, null), getType());
+        Object value = res.getObject(this, JavaSQLTypes.JDBC_DEFAULT, null);
+        Class<?> type = getType();
+        if (value == null && (type.isPrimitive() || Number.class.isAssignableFrom(type))) {
+            value = Filters.getDefaultForNull(Filters.wrap(type));
+        }
+        return Filters.convert(value, type);
     }
 
     public void calculateValue(Select sel, ExpContext ctx, ExpState state, 

openjpa-kernel/src/main/java/org/apache/openjpa/kernel/Filters.java

@@ -974,5 +974,19 @@ public class Filters {
              || Time.class.isAssignableFrom(c) 
              || Timestamp.class.isAssignableFrom(c));
     }
+    
+    public static Object getDefaultForNull(Class<?> nType) {
+        if (nType == Long.class) 
+            return new Long(0);
+        if (nType == Integer.class)
+            return new Integer(0);
+        if (nType == Double.class) 
+            return new Double(0.0);
+        if (nType == Float.class) 
+            return new Float(0.0);
+        if (nType == Short.class) 
+            return new Short((short)0);
+        return null;
+    }
 
 }

openjpa-persistence-jdbc/src/test/java/org/apache/openjpa/persistence/jdbc/query/TestAggregateQueryWithNoResult.java

@@ -0,0 +1,92 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.    
+ */
+package org.apache.openjpa.persistence.jdbc.query;
+
+import javax.persistence.EntityManager;
+
+import org.apache.openjpa.persistence.jdbc.query.domain.Chess;
+import org.apache.openjpa.persistence.jdbc.query.domain.Game;
+import org.apache.openjpa.persistence.jdbc.query.domain.IndoorGame;
+import org.apache.openjpa.persistence.jdbc.query.domain.Scrabble;
+import org.apache.openjpa.persistence.test.SingleEMFTestCase;
+
+/**
+ * Tests Aggregate Query that has no record.
+ * 
+ * SUM() and COUNT() always return Long.
+ * AVG(), MAX(), MIN() preserves the type of aggregated field.
+ * 
+ * @author Pinaki Poddar
+ * 
+ */
+public class TestAggregateQueryWithNoResult extends SingleEMFTestCase {
+    EntityManager em;
+	public void setUp() {
+        super.setUp(CLEAR_TABLES, Game.class, IndoorGame.class, Scrabble.class,
+				Chess.class);
+        em = emf.createEntityManager();
+        assertTrue(em.createQuery("select p from Scrabble p").getResultList().isEmpty());
+	}
+
+
+    public void testSumWithNoResult() {
+        String jpql = "SELECT SUM(g.nTile) FROM Scrabble g";
+
+        Long result = (Long)em.createQuery(jpql).getSingleResult();
+        
+        assertNotNull(result);
+        assertEquals(result, new Long(0));
+    }
+    
+    public void testAvgWithNoResult() {
+        String jpql = "SELECT AVG(g.nTile) FROM Scrabble g";
+
+        Integer result = (Integer)em.createQuery(jpql).getSingleResult();
+        
+        assertNotNull(result);
+        assertEquals(result, new Integer(0));
+    }
+    
+    public void testCountWithNoResult() {
+        String jpql = "SELECT COUNT(g.nTile) FROM Scrabble g";
+
+        Long result = (Long)em.createQuery(jpql).getSingleResult();
+        
+        assertNotNull(result);
+        assertEquals(result, new Long(0));
+    }
+    
+    public void testMaxWithNoResult() {
+        String jpql = "SELECT MAX(g.nTile) FROM Scrabble g";
+
+        Integer result = (Integer)em.createQuery(jpql).getSingleResult();
+       
+        assertNotNull(result);
+        assertEquals(result, new Integer(0));
+    }
+    
+    public void testMinWithNoResult() {
+        String jpql = "SELECT MIN(g.nTile) FROM Scrabble g";
+
+        Integer result = (Integer)em.createQuery(jpql).getSingleResult();
+        
+        assertNotNull(result);
+        assertEquals(result, new Integer(0));
+    }
+}