HHH-7246 - Fix and test

hibernate-envers/src/main/java/org/hibernate/envers/entities/mapper/SinglePropertyMapper.java

@@ -28,11 +28,13 @@ import java.util.Map;
 
 import org.hibernate.HibernateException;
 import org.hibernate.collection.spi.PersistentCollection;
+import org.hibernate.dialect.Oracle8iDialect;
 import org.hibernate.engine.spi.SessionImplementor;
 import org.hibernate.envers.configuration.AuditConfiguration;
 import org.hibernate.envers.entities.PropertyData;
 import org.hibernate.envers.exception.AuditException;
 import org.hibernate.envers.reader.AuditReaderImplementor;
+import org.hibernate.envers.tools.StringTools;
 import org.hibernate.envers.tools.Tools;
 import org.hibernate.envers.tools.reflection.ReflectionTools;
 import org.hibernate.property.DirectPropertyAccessor;
@@ -62,8 +64,12 @@ public class SinglePropertyMapper implements PropertyMapper, SimpleMapperBuilder
 
     public boolean mapToMapFromEntity(SessionImplementor session, Map<String, Object> data, Object newObj, Object oldObj) {
         data.put(propertyData.getName(), newObj);
-
-        return !Tools.objectsEqual(newObj, oldObj);
+        boolean dbLogicallyDifferent = true;
+        if ((session.getFactory().getDialect() instanceof Oracle8iDialect) && (newObj instanceof String || oldObj instanceof String)) {
+            // Don't generate new revision when database replaces empty string with NULL during INSERT or UPDATE statements.
+            dbLogicallyDifferent = !(StringTools.isEmpty((String) newObj) && StringTools.isEmpty((String) oldObj));
+        }
+        return dbLogicallyDifferent && !Tools.objectsEqual(newObj, oldObj);
     }
 
 	@Override

hibernate-envers/src/matrix/java/org/hibernate/envers/test/integration/basic/EmptyStringTest.java

@@ -0,0 +1,67 @@
+package org.hibernate.envers.test.integration.basic;
+
+import java.util.Arrays;
+import javax.persistence.EntityManager;
+
+import junit.framework.Assert;
+import org.junit.Test;
+
+import org.hibernate.dialect.Oracle8iDialect;
+import org.hibernate.envers.test.BaseEnversJPAFunctionalTestCase;
+import org.hibernate.envers.test.Priority;
+import org.hibernate.envers.test.entities.StrTestEntity;
+import org.hibernate.testing.RequiresDialect;
+import org.hibernate.testing.TestForIssue;
+
+/**
+ * @author Lukasz Antoniak (lukasz dot antoniak at gmail dot com)
+ */
+@TestForIssue(jiraKey = "HHH-7246")
+@RequiresDialect(Oracle8iDialect.class)
+public class EmptyStringTest extends BaseEnversJPAFunctionalTestCase {
+    private Integer emptyId = null;
+    private Integer nullId = null;
+
+    @Override
+    protected Class<?>[] getAnnotatedClasses() {
+        return new Class<?>[]{StrTestEntity.class};
+    }
+
+    @Test
+    @Priority(10)
+    public void initData() {
+        EntityManager em = getEntityManager();
+
+        // Revision 1
+        em.getTransaction().begin();
+        StrTestEntity emptyEntity = new StrTestEntity("");
+        em.persist(emptyEntity);
+        StrTestEntity nullEntity = new StrTestEntity(null);
+        em.persist(nullEntity);
+        em.getTransaction().commit();
+
+        emptyId = emptyEntity.getId();
+        nullId = nullEntity.getId();
+
+        em.close();
+        em = getEntityManager();
+
+        // Should not generate revision after NULL to "" modification and vice versa on Oracle.
+        em.getTransaction().begin();
+        emptyEntity = em.find(StrTestEntity.class, emptyId);
+        emptyEntity.setStr(null);
+        em.merge(emptyEntity);
+        nullEntity = em.find(StrTestEntity.class, nullId);
+        nullEntity.setStr("");
+        em.merge(nullEntity);
+        em.getTransaction().commit();
+
+        em.close();
+    }
+
+    @Test
+    public void testRevisionsCounts() {
+        Assert.assertEquals(Arrays.asList(1), getAuditReader().getRevisions(StrTestEntity.class, emptyId));
+        Assert.assertEquals(Arrays.asList(1), getAuditReader().getRevisions(StrTestEntity.class, nullId));
+    }
+}