[GEOT-6264] JDBC FeatureWriter-implementation annihilates input-data.

.gitignore

@@ -15,3 +15,4 @@ nb-configuration.xml
 workspace
 *.db
 .metadata
+.gradle

modules/library/jdbc/src/main/java/org/geotools/jdbc/JDBCFeatureReader.java

@@ -647,6 +647,9 @@ public void init() throws SQLException, IOException {
 
             // TODO: factory fid prefixing out
             init(featureType.getTypeName() + "." + dataStore.encodeFID(key, rs, offset));
+
+            for (int k = 0; k < values.length; k++) // ensure initialized values GEOT-6264
+            getAttribute(k);
         }
 
         public SimpleFeatureType getFeatureType() {

modules/library/jdbc/src/test/java/org/geotools/jdbc/JDBCFeatureWriterOnlineTest.java

@@ -0,0 +1,52 @@
+/*
+ *    GeoTools - The Open Source Java GIS Toolkit
+ *    http://geotools.org
+ *
+ *    (C) 2019, Open Source Geospatial Foundation (OSGeo)
+ *
+ *    This library is free software; you can redistribute it and/or
+ *    modify it under the terms of the GNU Lesser General Public
+ *    License as published by the Free Software Foundation;
+ *    version 2.1 of the License.
+ *
+ *    This library is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *    Lesser General Public License for more details.
+ */
+package org.geotools.jdbc;
+
+import org.geotools.data.FeatureWriter;
+import org.geotools.data.Transaction;
+import org.opengis.feature.simple.SimpleFeature;
+
+/**
+ * JDBC {@link FeatureWriter}-implementation tampers with input-data.
+ *
+ * @author Burkhard Strauss
+ * @see GEOT-6264
+ */
+public abstract class JDBCFeatureWriterOnlineTest extends JDBCTestSupport {
+
+    public void testNext() throws Exception {
+
+        try (FeatureWriter writer =
+                dataStore.getFeatureWriter(tname("ft1"), Transaction.AUTO_COMMIT)) {
+            assertTrue(writer.hasNext());
+            final SimpleFeature feature = (SimpleFeature) writer.next();
+            assertTrue(feature.getAttribute(0).toString().equals("POINT (0 0)"));
+            assertTrue((Integer) feature.getAttribute(1) == 0);
+            assertTrue((Double) feature.getAttribute(2) == 0.0);
+            assertTrue(((String) feature.getAttribute(3)).equals("zero"));
+        }
+        try (FeatureWriter writer =
+                dataStore.getFeatureWriter(tname("ft1"), Transaction.AUTO_COMMIT)) {
+            assertTrue(writer.hasNext());
+            final SimpleFeature feature = (SimpleFeature) writer.next();
+            assertTrue(feature.getAttribute(0).toString().equals("POINT (0 0)"));
+            assertTrue((Integer) feature.getAttribute(1) == 0);
+            assertTrue((Double) feature.getAttribute(2) == 0.0);
+            assertTrue(((String) feature.getAttribute(3)).equals("zero"));
+        }
+    }
+}

modules/plugin/jdbc/jdbc-mysql/src/test/java/org/geotools/data/mysql/MySQLFeatureWriterOnlineTest.java

@@ -0,0 +1,29 @@
+/*
+ *    GeoTools - The Open Source Java GIS Toolkit
+ *    http://geotools.org
+ *
+ *    (C) 2019, Open Source Geospatial Foundation (OSGeo)
+ *
+ *    This library is free software; you can redistribute it and/or
+ *    modify it under the terms of the GNU Lesser General Public
+ *    License as published by the Free Software Foundation;
+ *    version 2.1 of the License.
+ *
+ *    This library is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *    Lesser General Public License for more details.
+ */
+package org.geotools.data.mysql;
+
+import org.geotools.jdbc.JDBCFeatureWriterOnlineTest;
+import org.geotools.jdbc.JDBCTestSetup;
+
+/** @author Burkhard Strauss */
+public class MySQLFeatureWriterOnlineTest extends JDBCFeatureWriterOnlineTest {
+
+    @Override
+    protected JDBCTestSetup createTestSetup() {
+        return new MySQLTestSetup();
+    }
+}