[jira] [Commented] (NIFI-6145) Make groovy File functions available for FlowFile to simplify scripting

["Matt Burgess (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/NIFI-6145?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16801855#comment-16801855 ] 

Matt Burgess commented on NIFI-6145:
------------------------------------

We won't be able to add the methods to the FlowFile interface proper, as NiFi is written in pure Java so it doesn't know about Closures nor does it have access to Groovy classes such as ExpandoMetaClass.  In your script you can add the following methods to the top and it should give you what you want:


{code:java}
FlowFile.metaClass.withInputStream  = { Closure c -> 
   def inStream = session.read(delegate)
   c.call(inStream)
   inStream.close()
}

FlowFile.metaClass.withOutputStream  = { Closure c -> 
   def outStream = session.write(delegate)
   c.call(outStream)
   outStream.close()
}

FlowFile.metaClass.withReader = { String charset, Closure c -> 
   def inStream = session.read(delegate)
   def br = new BufferedReader(new InputStreamReader(inStream, charset))
   c.call(br)
   br.close()
}

FlowFile.metaClass.withWriter = { String charset, Closure c -> 
   def outStream = session.write(delegate)
   def bw = new BufferedWriter(new OutputStreamWriter(outStream, charset))
   c.call(bw)
   bw.close()
}
{code}


We could also add this to the script automatically before evaluating it, but that might throw the line numbers way off (although they are already off because we add imports for convenience).

IMO this is a better addition to ExecuteGroovyScript (EGS) rather than ExecuteScript, as it is specific to the Groovy language/idiom, which is what ExecuteGroovyScript is meant to take advantage of. I suppose we could add it to both but I think EGS is a better spot. That's if we even need to add it (since you can add the snippet above to scripts and get the capability). Thoughts?

> Make groovy File functions available for FlowFile to simplify scripting
> -----------------------------------------------------------------------
>
>                 Key: NIFI-6145
>                 URL: https://issues.apache.org/jira/browse/NIFI-6145
>             Project: Apache NiFi
>          Issue Type: New Feature
>            Reporter: Dmitry Lukyanov
>            Priority: Minor
>
> I'd like to add groovy File functions to a FlowFile class insige groovy script to make work with flowfie streams similar like we work with File in groovy.
> Object withInputStream(Closure closure)
> Create a new InputStream for this file and passes it into the closure.
>  Object 	withOutputStream(Closure closure)
> Creates a new OutputStream for this file and passes it into the closure. 
>  Object 	withReader(String charset, Closure closure)
> Create a new BufferedReader for this file using the specified charset and then passes it into the closure, ensuring the reader is closed after the closure returns. 
>  Object 	withWriter(String charset, Closure closure)
> Creates a new BufferedWriter for this file, passes it to the closure, and ensures the stream is flushed and closed after the closure returns. 
> etc...
> ----
> ready to contribute



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