A NiFi template using InvokeScriptedProcessor with Groovy to offer a GenerateFlowFile alternative that allows for setting the content and filename of a flow file

GenerateFlowFileWithContent.xml

<?xml version="1.0" encoding="UTF-8" standalone="yes"?><template><description>This template can be used like a GenerateFlowFile processor, where the content and filename can be specified. It uses InvokeScriptedProcessor and Groovy to achieve this.</description><name>GenerateFlowFileWithContent</name><snippet><processors><id>8e949039-0779-458d-b825-32b09ef80b38</id><parentGroupId>d3d19b0c-5876-41a2-8b09-e5ed911dfa67</parentGroupId><position><x>-172.94315107850957</x><y>-64.62506581228018</y></position><config><bulletinLevel>WARN</bulletinLevel><comments></comments><concurrentlySchedulableTaskCount>1</concurrentlySchedulableTaskCount><defaultConcurrentTasks><entry><key>TIMER_DRIVEN</key><value>1</value></entry><entry><key>EVENT_DRIVEN</key><value>0</value></entry><entry><key>CRON_DRIVEN</key><value>1</value></entry></defaultConcurrentTasks><defaultSchedulingPeriod><entry><key>TIMER_DRIVEN</key><value>0 sec</value></entry><entry><key>CRON_DRIVEN</key><value>* * * * * ?</value></entry></defaultSchedulingPeriod><descriptors><entry><key>Script Engine</key><value><allowableValues><displayName>ECMAScript</displayName><value>ECMAScript</value></allowableValues><allowableValues><displayName>Groovy</displayName><value>Groovy</value></allowableValues><allowableValues><displayName>lua</displayName><value>lua</value></allowableValues><allowableValues><displayName>python</displayName><value>python</value></allowableValues><allowableValues><displayName>ruby</displayName><value>ruby</value></allowableValues><defaultValue>ECMAScript</defaultValue><description>The engine to execute scripts</description><displayName>Script Engine</displayName><dynamic>false</dynamic><name>Script Engine</name><required>true</required><sensitive>false</sensitive><supportsEl>false</supportsEl></value></entry><entry><key>Script File</key><value><description>Path to script file to execute. Only one of Script File or Script Body may be used</description><displayName>Script File</displayName><dynamic>false</dynamic><name>Script File</name><required>false</required><sensitive>false</sensitive><supportsEl>true</supportsEl></value></entry><entry><key>Script Body</key><value><description>Body of script to execute. Only one of Script File or Script Body may be used</description><displayName>Script Body</displayName><dynamic>false</dynamic><name>Script Body</name><required>false</required><sensitive>false</sensitive><supportsEl>false</supportsEl></value></entry><entry><key>Module Directory</key><value><description>Comma-separated list of paths to files and/or directories which contain modules required by the script.</description><displayName>Module Directory</displayName><dynamic>false</dynamic><name>Module Directory</name><required>false</required><sensitive>false</sensitive><supportsEl>false</supportsEl></value></entry><entry><key>File Content</key><value><description>The content for the generated flow file</description><displayName>File Content</displayName><dynamic>false</dynamic><name>File Content</name><required>false</required><sensitive>false</sensitive><supportsEl>true</supportsEl></value></entry><entry><key>Evaluate Expressions in Content</key><value><allowableValues><displayName>true</displayName><value>true</value></allowableValues><allowableValues><displayName>false</displayName><value>false</value></allowableValues><defaultValue>false</defaultValue><description>Whether to evaluate NiFi Expression Language constructs within the content</description><displayName>Evaluate Expressions in Content</displayName><dynamic>false</dynamic><name>Evaluate Expressions in Content</name><required>true</required><sensitive>false</sensitive><supportsEl>false</supportsEl></value></entry><entry><key>Filename</key><value><description>The name of the flow file to be stored in the filename attribute</description><displayName>Filename</displayName><dynamic>false</dynamic><name>Filename</name><required>false</required><sensitive>false</sensitive><supportsEl>true</supportsEl></value></entry></descriptors><lossTolerant>false</lossTolerant><penaltyDuration>30 sec</penaltyDuration><properties><entry><key>Script Engine</key><value>Groovy</value></entry><entry><key>Script File</key></entry><entry><key>Script Body</key><value>class GenerateFlowFileWithContent implements Processor {

    def REL_SUCCESS = new Relationship.Builder()
            .name('success')
            .description('The flow file with the specified content and/or filename was successfully transferred')
            .build();

    def CONTENT = new PropertyDescriptor.Builder()
            .name('File Content').description('The content for the generated flow file')
            .required(false).expressionLanguageSupported(true).addValidator(Validator.VALID).build()
    
    def CONTENT_HAS_EL = new PropertyDescriptor.Builder()
            .name('Evaluate Expressions in Content').description('Whether to evaluate NiFi Expression Language constructs within the content')
            .required(true).allowableValues('true','false').defaultValue('false').build()
            
    def FILENAME = new PropertyDescriptor.Builder()
            .name('Filename').description('The name of the flow file to be stored in the filename attribute')
            .required(false).expressionLanguageSupported(true).addValidator(StandardValidators.NON_EMPTY_VALIDATOR).build()
    
    @Override
    void initialize(ProcessorInitializationContext context) { }

    @Override
    Set&lt;Relationship&gt; getRelationships() { return [REL_SUCCESS] as Set }

    @Override
    void onTrigger(ProcessContext context, ProcessSessionFactory sessionFactory) throws ProcessException {
      try {
        def session = sessionFactory.createSession()
        def flowFile = session.create()
        
        def hasEL = context.getProperty(CONTENT_HAS_EL).asBoolean()
        def contentProp = context.getProperty(CONTENT)
        def content = (hasEL ? contentProp.evaluateAttributeExpressions().value : contentProp.value) ?: ''
        def filename = context.getProperty(FILENAME)?.evaluateAttributeExpressions()?.getValue()
        
        flowFile = session.write(flowFile, { outStream -&gt;
                outStream.write(content.getBytes(&quot;UTF-8&quot;))
            } as OutputStreamCallback)
        
        if(filename != null) { flowFile = session.putAttribute(flowFile, 'filename', filename) }
        // transfer
        session.transfer(flowFile, REL_SUCCESS)
        session.commit()
      } catch(e) {
          throw new ProcessException(e)
      }
    }

    @Override
    Collection&lt;ValidationResult&gt; validate(ValidationContext context) { return null }

    @Override
    PropertyDescriptor getPropertyDescriptor(String name) {
        switch(name) {
            case 'File Content': return CONTENT
            case 'Evaluate Expressions in Content': return CONTENT_HAS_EL
            case 'Filename': return FILENAME
            default: return null
        }
    }

    @Override
    void onPropertyModified(PropertyDescriptor descriptor, String oldValue, String newValue) { }

    @Override
    List&lt;PropertyDescriptor&gt; getPropertyDescriptors() { return [CONTENT, CONTENT_HAS_EL, FILENAME] as List }

    @Override
    String getIdentifier() { return 'GenerateFlowFile-InvokeScriptedProcessor' }
    
}

processor = new GenerateFlowFileWithContent()</value></entry><entry><key>Module Directory</key></entry><entry><key>File Content</key></entry><entry><key>Evaluate Expressions in Content</key><value>false</value></entry><entry><key>Filename</key></entry></properties><runDurationMillis>0</runDurationMillis><schedulingPeriod>3 sec</schedulingPeriod><schedulingStrategy>TIMER_DRIVEN</schedulingStrategy><yieldDuration>1 sec</yieldDuration></config><name>GenerateFlowFileWithContent</name><relationships><autoTerminate>false</autoTerminate><description>The flow file with the specified content and/or filename was successfully transferred</description><name>success</name></relationships><state>STOPPED</state><style/><supportsEventDriven>false</supportsEventDriven><supportsParallelProcessing>true</supportsParallelProcessing><type>org.apache.nifi.processors.script.InvokeScriptedProcessor</type></processors></snippet><timestamp>02/24/2016 17:34:25 EST</timestamp></template>