Andy,
Thank you for your detailed example. Unfortunately I don’t know Groovy though
from your example I see that it’s syntax is Scala-like and rather transparent.
My preference at this point is to use pure Java, if possible.
I managed to get my Java class executed by composing the following pipeline.
GenerateFlowFile -> ExecuteStreamCommand -> PutFile
|
\/
jar with custom Java class
The hardest part was figuring out that I must place GenerateFlowFile processor
before ExecuteStreamCommand in order for it to work.
While documentation of ExecuteStreamCommand processor says that it must have an
incoming connection, it says nothing about how to go about creating it. This is
especially counterintuitive when a custom Java class jar doesn’t need any input
from NiFi flow. It’s a kind of a situation where one really wishes for a
cookbook on NiFi.
From: Andy LoPresto [mailto:alopre...@apache.org]
Sent: Monday, July 16, 2018 1:21 PM
To: users@nifi.apache.org
Subject: Re: NiFi processor to execute a Java class
You can execute arbitrary Java logic via ExecuteScript and
InvokeScriptedProcessor as well. Simply import the relevant Java class as
usual, and invoke the methods as you would in any other scenario. It will be
easiest to do this with Groovy as your scripting language, and ensure that the
JAR containing the classes is available in the “modules” directory configured
on the processor.
import org.apache.commons.io.IOUtils
import java.nio.charset.*
import com.jhancock.CustomService
def flowFile = session.get()
if(!flowFile) return
flowFile = session.write(flowFile, {inputStream, outputStream ->
// For demo purpose only; this is not memory-nice
def flowFileContents = IOUtils.toString(inputStream, StandardCharsets.UTF_8)
// Do something with your service
CustomService myCustomService = new CustomService()
def result = myCustomService.doSomething(flowFileContents)
outputStream.write(result.getBytes(StandardCharsets.UTF_8))
} as StreamCallback)
flowFile = session.putAttribute(flowFile, ‘custom_service_performed', ’true')
session.transfer(flowFile, REL_SUCCESS)
Andy LoPresto
alopre...@apache.org<mailto:alopre...@apache.org>
alopresto.apa...@gmail.com<mailto:alopresto.apa...@gmail.com>
PGP Fingerprint: 70EC B3E5 98A6 5A3F D3C4 BACE 3C6E F65B 2F7D EF69
On Jul 16, 2018, at 8:23 AM, Mike Thomsen
<mikerthom...@gmail.com<mailto:mikerthom...@gmail.com>> wrote:
As far as I know, it'll capture the stdout/stderr output of your Java class and
send that to a flowfile. Anything beyond that you'd need to do yourself.
On Mon, Jul 16, 2018 at 11:18 AM Vitaly Krivoy
<vitaly_kri...@jhancock.com<mailto:vitaly_kri...@jhancock.com>> wrote:
Thank you Mike. The objective of my custom class is to query data from
salesforce. Will ExecuteStreamCommand processor automatically capture the
output of my custom Java class and generate flow files, or do I have to
implement this capability myself?
From: Mike Thomsen
[mailto:mikerthom...@gmail.com<mailto:mikerthom...@gmail.com>]
Sent: Monday, July 16, 2018 11:07 AM
To: users@nifi.apache.org<mailto:users@nifi.apache.org>
Subject: Re: NiFi processor to execute a Java class
The REPL is not going to help unless it provides a ScriptEngine implementation,
which I don't believe it does. At this point, I think your only option between
the three is ExecuteStreamCommand.
On Mon, Jul 16, 2018 at 10:54 AM Vitaly Krivoy
<vitaly_kri...@jhancock.com<mailto:vitaly_kri...@jhancock.com>> wrote:
What would be the best NiFi processor to execute a Java class? I’ve seen some
references to ExecuteScript, InvokeScriptedProcessor and ExecuteStreamCommand
processors, but nothing conclusive. Speaking of ExecuteScript processor - would
it work with Java 8, or should it be used with Java 9 or later because those
releases have a REPL loop? Thanks.
Vitaly Krivoy
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