Correctly handle NVARCHAR, LONGNVARCHAR and NCLOBs

Issue: SPR-16154

spring-jdbc/src/main/java/org/springframework/jdbc/core/StatementCreatorUtils.java

@@ -68,13 +68,16 @@ public abstract class StatementCreatorUtils {
 	 * System property that instructs Spring to ignore {@link java.sql.ParameterMetaData#getParameterType}
 	 * completely, i.e. to never even attempt to retrieve {@link PreparedStatement#getParameterMetaData()}
 	 * for {@link StatementCreatorUtils#setNull} calls.
-	 * <p>The default is "false", trying {@code getParameterType} calls first and falling back to
+	 * <p>The effective default is "false", trying {@code getParameterType} calls first and falling back to
 	 * {@link PreparedStatement#setNull} / {@link PreparedStatement#setObject} calls based on well-known
 	 * behavior of common databases. Spring records JDBC drivers with non-working {@code getParameterType}
 	 * implementations and won't attempt to call that method for that driver again, always falling back.
 	 * <p>Consider switching this flag to "true" if you experience misbehavior at runtime, e.g. with
 	 * a connection pool setting back the {@link PreparedStatement} instance in case of an exception
 	 * thrown from {@code getParameterType} (as reported on JBoss AS 7).
+	 * <p>Note that this flag is "true" by default on Oracle 12c since there can be leaks created by
+	 * {@code getParameterType} calls in such a scenario. You need to explicitly set the flag to
+	 * "false" in order to enforce the use of {@code getParameterType} against Oracle drivers.
 	 */
 	public static final String IGNORE_GETPARAMETERTYPE_PROPERTY_NAME = "spring.jdbc.getParameterType.ignore";
 
@@ -339,10 +342,12 @@ public abstract class StatementCreatorUtils {
 		else if (inValue instanceof SqlValue) {
 			((SqlValue) inValue).setValue(ps, paramIndex);
 		}
-		else if (sqlType == Types.VARCHAR || sqlType == Types.NVARCHAR ||
-				sqlType == Types.LONGVARCHAR || sqlType == Types.LONGNVARCHAR) {
+		else if (sqlType == Types.VARCHAR || sqlType == Types.LONGVARCHAR ) {
 			ps.setString(paramIndex, inValue.toString());
 		}
+		else if (sqlType == Types.NVARCHAR || sqlType == Types.LONGNVARCHAR) {
+			ps.setNString(paramIndex, inValue.toString());
+		}
 		else if ((sqlType == Types.CLOB || sqlType == Types.NCLOB) && isStringValue(inValue.getClass())) {
 			String strVal = inValue.toString();
 			if (strVal.length() > 4000) {
@@ -364,8 +369,13 @@ public abstract class StatementCreatorUtils {
 					logger.debug("JDBC driver does not support JDBC 4.0 'setClob(int, Reader, long)' method", ex);
 				}
 			}
-			// Fallback: regular setString binding
-			ps.setString(paramIndex, strVal);
+			// Fallback: setString or setNString binding
+			if (sqlType == Types.NCLOB) {
+				ps.setNString(paramIndex, strVal);
+			}
+			else {
+				ps.setString(paramIndex, strVal);
+			}
 		}
 		else if (sqlType == Types.DECIMAL || sqlType == Types.NUMERIC) {
 			if (inValue instanceof BigDecimal) {