[
https://issues.apache.org/jira/browse/NIFI-2791?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15604687#comment-15604687
]
ASF GitHub Bot commented on NIFI-2791:
--------------------------------------
Github user pvillard31 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/1157#discussion_r84855173
--- Diff:
nifi-commons/nifi-expression-language/src/main/java/org/apache/nifi/attribute/expression/language/evaluation/functions/MathEvaluator.java
---
@@ -0,0 +1,138 @@
+/*
+ * 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.nifi.attribute.expression.language.evaluation.functions;
+
+import org.apache.nifi.attribute.expression.language.evaluation.Evaluator;
+import
org.apache.nifi.attribute.expression.language.evaluation.NumberEvaluator;
+import
org.apache.nifi.attribute.expression.language.evaluation.NumberQueryResult;
+import
org.apache.nifi.attribute.expression.language.evaluation.QueryResult;
+import
org.apache.nifi.attribute.expression.language.exception.AttributeExpressionLanguageException;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Map;
+
+public class MathEvaluator extends NumberEvaluator {
+
+ private final Evaluator<Number> subject;
+ private final Evaluator<String> methodName;
+ private final Evaluator<Number> optionalArg;
+
+ public MathEvaluator(final Evaluator<Number> subject, final
Evaluator<String> methodName, final Evaluator<Number> optionalArg) {
+ this.subject = subject;
+ this.methodName = methodName;
+ this.optionalArg = optionalArg;
+ }
+
+ @Override
+ public QueryResult<Number> evaluate(final Map<String, String>
attributes) {
+ final String methodNamedValue =
methodName.evaluate(attributes).getValue();
+ if (methodNamedValue == null) {
+ return new NumberQueryResult(null);
+ }
+
+ final Number subjectValue;
+ if(subject != null) {
+ subjectValue = subject.evaluate(attributes).getValue();
+ if(subjectValue == null){
+ return new NumberQueryResult(null);
+ }
+ } else {
+ subjectValue = null;
+ }
+
+ final Number optionalArgValue;
+ if(optionalArg != null) {
+ optionalArgValue = optionalArg.evaluate(attributes).getValue();
+
+ if(optionalArgValue == null) {
+ return new NumberQueryResult(null);
+ }
+ } else {
+ optionalArgValue = null;
+ }
+
+ try {
+ Number executionValue = null;
+
+ if (subjectValue == null){
+ Method method = Math.class.getMethod(methodNamedValue);
+
+ if(method == null) {
+ throw new AttributeExpressionLanguageException("Cannot
evaluate 'math' function because no subjectless method was found with the
name:'" + methodNamedValue + "'");
+ }
+
+ executionValue = (Number) method.invoke(null);
+ } else if(optionalArg == null) {
+ boolean subjectIsDecimal = subjectValue instanceof Double;
+ Method method = Math.class.getMethod(methodNamedValue,
subjectIsDecimal ? double.class : long.class);
--- End diff --
If I use:
````
${filename:math('exp')}
````
I'll get the following exception:
````
org.apache.nifi.attribute.expression.language.exception.AttributeExpressionLanguageException:
Unable to calculate math function value
at
org.apache.nifi.attribute.expression.language.evaluation.functions.MathEvaluator.evaluate(MathEvaluator.java:129)
~[nifi-expression-language-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.attribute.expression.language.Query.evaluate(Query.java:568)
~[nifi-expression-language-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.attribute.expression.language.Query.evaluateExpression(Query.java:386)
~[nifi-expression-language-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.attribute.expression.language.StandardPreparedQuery.evaluateExpressions(StandardPreparedQuery.java:48)
~[nifi-expression-language-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.attribute.expression.language.StandardPropertyValue.evaluateAttributeExpressions(StandardPropertyValue.java:152)
~[nifi-expression-language-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.attribute.expression.language.StandardPropertyValue.evaluateAttributeExpressions(StandardPropertyValue.java:133)
~[nifi-expression-language-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.processors.attributes.UpdateAttribute.executeActions(UpdateAttribute.java:496)
~[na:na]
at
org.apache.nifi.processors.attributes.UpdateAttribute.onTrigger(UpdateAttribute.java:377)
~[na:na]
at
org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27)
~[nifi-api-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1064)
~[nifi-framework-core-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:136)
[nifi-framework-core-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47)
[nifi-framework-core-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:132)
[nifi-framework-core-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
at
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[na:1.8.0_77]
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
[na:1.8.0_77]
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
[na:1.8.0_77]
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
[na:1.8.0_77]
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
[na:1.8.0_77]
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
[na:1.8.0_77]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_77]
Caused by: java.lang.NoSuchMethodException: java.lang.Math.exp(long)
at java.lang.Class.getMethod(Class.java:1786) ~[na:1.8.0_77]
at
org.apache.nifi.attribute.expression.language.evaluation.functions.MathEvaluator.evaluate(MathEvaluator.java:82)
~[nifi-expression-language-1.1.0-SNAPSHOT.jar:1.1.0-SNAPSHOT]
... 19 common frames omitted
````
I know this is because I didn't use ``toDecimal()`` but I am wondering if
you were not expecting to throw the custom exception just few lines after? IMO
just throwing the current exception may not be very clear to users trying to
understand why it didn't work. I think users may forget to cast arguments and
this will probably be the most common mistake, it could be useful to remember
this "requirement" in the exception message. Thoughts?
> Create a new Expression Language Function to support Java.lang.Math operations
> ------------------------------------------------------------------------------
>
> Key: NIFI-2791
> URL: https://issues.apache.org/jira/browse/NIFI-2791
> Project: Apache NiFi
> Issue Type: Improvement
> Reporter: Joseph Percivall
> Assignee: Joseph Percivall
> Fix For: 1.1.0
>
>
> Once EL is improved to support decimals (NIFI-1662) it will be desired to
> support higher level math functions than are currently implemented. The
> easiest way to do this is to provide access to the Math class[1]. This should
> provide all the building blocks necessary to do any desired operations on
> decimals.
> [1] https://docs.oracle.com/javase/7/docs/api/java/lang/Math.html
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