问题描述
我正在尝试在NiFi中创建一个Python脚本:
I am trying to create a Python script in NiFi that:
- 从传入的流文件中读取一些属性
- 读取流文件的json内容&提取特定字段
- 将属性写入传出的流文件
- 用脚本中创建的新内容覆盖传入的流文件(例如，返回新json的API调用)，然后将其发送到SUCCESS关系，或者删除旧的流文件并使用所需的内容创建新的流文件.
到目前为止我所做的事情:
What i ve done so far:
import json
import java.io
from org.apache.commons.io import IOUtils
from java.nio.charset import StandardCharsets
from org.apache.nifi.processor.io import StreamCallback,InputStreamCallback, OutputStreamCallback
class OutputWrite(OutputStreamCallback, obj):
def __init__(self):
self.obj = obj
def process(self, outputStream):
outputStream.write(bytearray(json.dumps(self.obj).encode('utf')))
###end class###
flowfile = session.get()
if flowfile != None:
**#1) Get flowfile attributes**
headers = {
'Accept-Encoding': 'gzip, deflate, br',
'Accept': 'application/json, text/plain, */*',
'Cache-Control': 'no-cache',
'Ocp-Apim-Trace': 'true',
'Authorization': flowfile.getAttribute('Authorization')
}
collection = flowfile.getAttribute('collection')
dataset = flowfile.getAttribute('dataset')
**#2)Get flowfile content**
stream_content = session.read(flowfile)
text_content = IOUtils.toString(stream_content, StandardCharsets.UTF_8)
json_content = json.loads(text_content)
records = json_content['result']['count']
pages = records/10000
**#3) Write flowfile attributes**
flowfile = session.putAttribute(flowfile, 'collection', collection)
flowfile = session.putAttribute(flowfile, 'dataset', dataset)
**#API operations: output_json with desired data**
output_json = {some data}
**#4) Write final JSON data to output flowfile**
flowfile = session.write(flowfile, OutputWrite(output_json))
session.transfer(flowfile, REL_SUCCESS)
session.commit()
我的问题是我找不到在OutputStreamCallback类中将对期望的output_json对象的引用作为参数传递的方法.关于如何解决这个问题或更好的方法的任何想法?
My problem is that i can't find a way to pass a reference to the desired output_json object as an argument in the OutputStreamCallback class. Any ideas on how to resolve this or maybe a better approach?
在这种情况下，在类的流程函数中执行所有API操作也许更容易，但是然后我如何才能访问流程函数中的传入流文件属性(需要会话或流文件对象)?
Is it maybe easier to perform all API operations in this case within the process function of the class, but then how do i get access to the incoming flowfile attributes within the process function (requires a session or a flowfile object) ?
任何帮助，不胜感激！
推荐答案
我在下面提供了示例Python代码，该代码允许自定义 PyStreamCallback 类，该类实现了将流文件内容中的JSON转换为逻辑的逻辑.马特·伯吉斯的博客文章，但我鼓励您考虑对 UpdateAttribute 和 EvaluateJSONPath 使用本机处理器来执行相关活动，并且仅在执行NiFi任务特别需要的地方使用自定义代码开箱即用.
I've included example Python code below which allows for a custom PyStreamCallback class which implements logic to transform JSON in the flowfile content from Matt Burgess' blog article on the topic, but I would encourage you to consider using native processors for UpdateAttribute and EvaluateJSONPath to perform the relevant activities and only use custom code where it is specifically needed to perform a task that NiFi doesn't handle out of the box.
import json
import java.io
from org.apache.commons.io import IOUtils
from java.nio.charset import StandardCharsets
from org.apache.nifi.processor.io import StreamCallback
class PyStreamCallback(StreamCallback):
def __init__(self):
pass
def process(self, inputStream, outputStream):
text = IOUtils.toString(inputStream, StandardCharsets.UTF_8)
obj = json.loads(text)
newObj = {
"Range": 5,
"Rating": obj['rating']['primary']['value'],
"SecondaryRatings": {}
}
for key, value in obj['rating'].iteritems():
if key != "primary":
newObj['SecondaryRatings'][key] = {"Id": key, "Range": 5, "Value": value['value']}
outputStream.write(bytearray(json.dumps(newObj, indent=4).encode('utf-8')))
flowFile = session.get()
if (flowFile != None):
flowFile = session.write(flowFile,PyStreamCallback())
flowFile = session.putAttribute(flowFile, "filename", flowFile.getAttribute('filename').split('.')[0]+'_translated.json')
session.transfer(flowFile, REL_SUCCESS)
更新:
要在回调中访问流文件的属性，只需将其作为参数传递给构造函数，将其存储为字段，然后在 process 方法内对其进行引用.这是一个非常简单的示例，将属性 my_attr 的值连接到传入的流文件内容并将其写回:
To access the attributes of the flowfile within the callback, simply pass it as an argument to the constructor, store it as a field, and reference it within the process method. Here is a very simple example that concatenates the value of attribute my_attr to the incoming flowfile content and writes it back:
import json
import java.io
from org.apache.commons.io import IOUtils
from java.nio.charset import StandardCharsets
from org.apache.nifi.processor.io import StreamCallback
class PyStreamCallback(StreamCallback):
def __init__(self, flowfile):
self.ff = flowfile
pass
def process(self, inputStream, outputStream):
text = IOUtils.toString(inputStream, StandardCharsets.UTF_8)
text += self.ff.getAttribute('my_attr')
outputStream.write(bytearray(text.encode('utf-8')))
flowFile = session.get()
if (flowFile != None):
flowFile = session.write(flowFile,PyStreamCallback(flowFile))
session.transfer(flowFile, REL_SUCCESS)
传入流文件:
--------------------------------------------------
Standard FlowFile Attributes
Key: 'entryDate'
Value: 'Tue Mar 13 13:10:48 PDT 2018'
Key: 'lineageStartDate'
Value: 'Tue Mar 13 13:10:48 PDT 2018'
Key: 'fileSize'
Value: '30'
FlowFile Attribute Map Content
Key: 'filename'
Value: '1690494181462176'
Key: 'my_attr'
Value: 'This is an attribute value.'
Key: 'path'
Value: './'
Key: 'uuid'
Value: 'dc93b715-50a0-43ce-a4db-716bd9ec3205'
--------------------------------------------------
This is some flowfile content.
去向流文件:
--------------------------------------------------
Standard FlowFile Attributes
Key: 'entryDate'
Value: 'Tue Mar 13 13:10:48 PDT 2018'
Key: 'lineageStartDate'
Value: 'Tue Mar 13 13:10:48 PDT 2018'
Key: 'fileSize'
Value: '57'
FlowFile Attribute Map Content
Key: 'filename'
Value: '1690494181462176'
Key: 'my_attr'
Value: 'This is an attribute value.'
Key: 'path'
Value: './'
Key: 'uuid'
Value: 'dc93b715-50a0-43ce-a4db-716bd9ec3205'
--------------------------------------------------
This is some flowfile content.This is an attribute value.
这篇关于NiFi中的Python ExecuteScript:转换流文件属性&内容的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！