Github user nickwallen commented on a diff in the pull request:
https://github.com/apache/metron/pull/884#discussion_r159497380
--- Diff:
metron-stellar/stellar-common/src/main/java/org/apache/metron/stellar/common/shell/StellarExecutionNotifier.java
---
@@ -0,0 +1,44 @@
+/*
+ *
+ * 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.metron.stellar.common.shell;
+
+/**
+ * Notifies listeners when events occur during the execution of Stellar
expressions.
+ */
+public interface StellarExecutionNotifier {
+
+ /**
+ * Add a listener that will be notified when a magic command is defined.
+ * @param listener The listener to notify.
+ */
+ void addSpecialListener(StellarExecutionListeners.SpecialDefinedListener
listener);
--- End diff --
Our `DefaultStellarShellExecutor` is a `StellarExecutionNotifier` as it is
able to notify event listeners when variables, functions or specials are
defined.
---
