Github user cestella commented on a diff in the pull request:
https://github.com/apache/incubator-metron/pull/312#discussion_r83660563
--- Diff:
metron-platform/metron-common/src/main/java/org/apache/metron/common/dsl/functions/SystemFunctions.java
---
@@ -0,0 +1,75 @@
+/**
+ * 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.common.dsl.functions;
+
+import org.apache.metron.common.dsl.BaseStellarFunction;
+import org.apache.metron.common.dsl.Stellar;
+import org.apache.metron.common.system.Environment;
+
+import java.util.List;
+
+public class SystemFunctions {
+
+ @Stellar(namespace = "SYSTEM",
+ name = "ENV_GET",
+ description = "Returns the value associated with an environment
variable",
+ params = {
+ "env_var - Environment variable name to get the value
for"
+ },
+ returns = "String"
+ )
+ public static class EnvGet extends BaseStellarFunction {
+ private Environment env;
+
+ public EnvGet() {
+ this(new Environment());
+ }
+
+ public EnvGet(Environment env) {
+ this.env = env;
+ }
+
+ @Override
+ public Object apply(List<Object> args) {
+ if (args.size() == 0) {
+ return null;
+ } else {
+ return env.get((String) args.get(0));
--- End diff --
Well, if we were going to coerce strings, I'd suggest using the
`ConversionUtils` stuff just for consistency. I had thought of suggesting
coercing the argument, but I couldn't imagine any situation where the coerced
string would be what I would want. Like, if you passed in a list or a number
accidentally, would you rather coercion or just return null?
I guess the argument for coercion is it does no harm. If there's no
environment variable, then fine, then it'll return null anyway. If there is,
then you have done good. I don't know, I am fine with either way.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
