question Nifi - Java Reflection Processor in Archives of Support Questions (Read Only)

Nifi - Java Reflection Processor

gbraccialli3 — Wed, 27 Apr 2016 10:12:34 GMT

Is there a NiFi processor where I can pass a java class name, method name and arguments and get results? Similar to Hive reflect UDF.

I found ExecuteStreamCommand (which seems to do the same with OS commands) and ExecuteScript (but not sure if it's possible to call java methods using NiFi script language).

Thanks.

Re: Nifi - Java Reflection Processor

aervits — Wed, 27 Apr 2016 10:17:51 GMT

ExecuteScript accepts Groovy, which is a jvm language.

Re: Nifi - Java Reflection Processor

mburgess — Wed, 27 Apr 2016 10:34:45 GMT

To @Artem Ervits comment, if the Java class is available in the class loader (either by being part of the NiFi Core or being specified as a JAR in the ExecuteScript's Module Directory property), then you can call it directly, you don't need reflection.

If I'm not answering your question, can you provide more details? I'm happy to help 🙂

Re: Nifi - Java Reflection Processor

gbraccialli3 — Wed, 27 Apr 2016 10:35:59 GMT

Thanks @Artem Ervits, yes I remember your Groovy great post for hive. Would you have and groovy example for NiFi as well?

Re: Nifi - Java Reflection Processor

aervits — Wed, 27 Apr 2016 11:04:39 GMT

I'm actually posting link to Matt's blog for an example http://funnifi.blogspot.com/2016/04/sql-in-nifi-with-executescript.html

Re: Nifi - Java Reflection Processor

gbraccialli3 — Wed, 27 Apr 2016 11:04:42 GMT

Thanks @mburgess.

Imagine, hypothetically, I want to call a static method passing a string as parameter, like reserve from Apache Commons StringUtils. Would something like this work?

org.apache.commons.lang3.StringUtils.reverse( ${my_nifi_attribute} )

Re: Nifi - Java Reflection Processor

mburgess — Wed, 27 Apr 2016 11:27:39 GMT

Absolutely! with ExecuteScript (with, say, Groovy as the language), a script body could be something like:

import org.apache.commons.lang3.StringUtils
flowFile = session.get()
if(!flowFile) return
flowFile = session.putAttribute('my_nifi_attribute', StringUtils.reverse( flowFile.getAttribute('my_nifi_attribute') )
session.transfer(flowFile, REL_SUCCESS)

Re: Nifi - Java Reflection Processor

gbraccialli3 — Wed, 27 Apr 2016 11:36:05 GMT

Awesome! Thank you.

This is much easier than writing a custom processor.

Re: Nifi - Java Reflection Processor

aervits — Wed, 27 Apr 2016 20:05:50 GMT

@Guilherme Braccialli @mburgess a slightly modified version could include native Groovy reverse() method

http://docs.groovy-lang.org/2.4.0/html/api/org/codehaus/groovy/runtime/StringGroovyMethods.html#reverse(java.lang.CharSequence)

Re: Nifi - Java Reflection Processor

rdadi1 — Fri, 13 May 2016 22:33:32 GMT

Hi burgess I've tried to invoke stringutils.reverse() in the same u have suggested. what the processor will propagate on successexection ? Will it propagate reversed string on success?