Misc platform fixes (#1157)

* Oracle does not return row count - so we probably cannot detect Optimistic locking

* DB2 wants a varchar null value (other platfroms are happy with this, too)

* FIX Test for DB2 platform

src/main/java/io/ebeaninternal/server/core/PersistRequestBean.java

@@ -31,6 +31,7 @@ import io.ebeanservice.docstore.api.DocStoreUpdates;
 import javax.persistence.OptimisticLockException;
 import javax.persistence.PersistenceException;
 import java.io.IOException;
+import java.sql.Statement;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -784,8 +785,12 @@ public final class PersistRequestBean<T> extends PersistRequest implements BeanP
   @Override
   public final void checkRowCount(int rowCount) {
     if (ConcurrencyMode.VERSION == concurrencyMode && rowCount != 1) {
-      String m = Message.msg("persist.conc2", String.valueOf(rowCount));
-      throw new OptimisticLockException(m, null, bean);
+      // fix for oracle.
+      // see: https://stackoverflow.com/questions/19022175/executebatch-method-return-array-of-value-2-in-java
+      if (rowCount != Statement.SUCCESS_NO_INFO) {
+        String m = Message.msg("persist.conc2", String.valueOf(rowCount));
+        throw new OptimisticLockException(m, null, bean);
+      }
     }
     switch (type) {
       case DELETE:

src/main/java/io/ebeaninternal/server/type/ScalarTypeJsonObjectMapper.java

@@ -184,7 +184,7 @@ public class ScalarTypeJsonObjectMapper {
         bind.setObject(PostgresHelper.asObject(pgType, rawJson));
       } else {
         if (value == null) {
-          bind.setNull(Types.LONGNVARCHAR); // use longvarchar, otherwise SqlServer will fail with 'Invalid JDBC data type 5.001.'
+          bind.setNull(Types.VARCHAR); // use varchar, otherwise SqlServer/db2 will fail with 'Invalid JDBC data type 5.001.'
         } else {
           try {
             String json = objectMapper.writeValueAsString(value);