Now that we know some methods for parsing JSON data, let’s look at the REST and how we can use it to generate a url for our code. There are four parameters that we need to fill out for it to return a result. These four parameters are the Where, Out Fields, and Return Geometry, and return format. If you need a more specific result, you can enter more parameters as needed.
The base url for the query is looks like this from Query: BLM California Active Fires 2023 (ID: 0) [1].
With the query at the end followed by the ?. The ? separates the url into sections. This ? is starting the passing of the parameters, which are separated by & sign. Note that the url does not contain spaces
The complete request’s parameters are added to the URL when the request is submitted:
?where=1=1&objectIds=&time=&geometry=&geometryType=esriGeometryEnvelope&inSR=&spatialRel=esriSpatialRelIntersects&resultType=none&distance=0.0&units=esriSRUnit_Meter&relationParam=&returnGeodetic=false&outFields=*&returnGeometry=true&featureEncoding=esriDefault&multipatchOption=xyFootprint&maxAllowableOffset=&geometryPrecision=&outSR=&defaultSR=&datumTransformation=&applyVCSProjection=false&returnIdsOnly=false&returnUniqueIdsOnly=false&returnCountOnly=false&returnExtentOnly=false&returnQueryGeometry=false&returnDistinctValues=false&cacheHint=false&orderByFields=&groupByFieldsForStatistics=&outStatistics=&having=&resultOffset=&resultRecordCount=&returnZ=false&returnM=false&returnExceededLimitFeatures=true&quantizationParameters=&sqlFormat=none&f=json&token=
Building our query that will return all features, all fields in json format will look like:
https://www.arcgis.com/apps/mapviewer/index.html?url=https://services3.arcgis.com/T4QMspbfLg3qTGWY/ArcGIS/rest/services/Boulder_Fire_Tax_District/FeatureServer/0/query?where=1=1&outFields=*&returnGeometry=true &f=json
With this url string, can use request to retrieve data from services and save them locally. There are a few ways of doing this such as using pandas to read the url, converting the json to a dataframe and then to a featureclass, converting the JSON result to a dictionary and using an insert/update cursor, or creating a new featureclass using the arcpy method JSONToFeatures_conversion(…) method. It is important to note an important aspect of this method noted in the Summary section of the documentation:
Converts feature collections in an Esri JSON formatted file (.json) or a GeoJSON formatted file (.geojson) to a feature class.
This means that the method is expecting a file as the input and trying to pass the response json will results in an error and if you do not need to manipulate the data before outputting to a featureclass, this method might be the simplest to implement with the least amount of packages. If you need to work on the data, such as convert the datetimes for a field, converting the JSON to a dataframe or dictionary would be the preferred process.
Below is an example of the process.
import arcpy
import requests
import json
arcpy.env.overwriteOutput = True
url = " https://services3.arcgis.com/T4QMspbfLg3qTGWY/ArcGIS/rest/services/Boulder_Fire_Tax_District/FeatureServer/0/query?where=1=1&returnGeometry=true&outFields=*&f=json"
# send the request to the url and store the reply as response
response = requests.get(url)
# Get result as json
jsonCode = response.json()
jsonFile = r"C:\NGA\Lesson 3\response.json"
# write the response json to a file
with open(jsonFile, "w") as outfile:
json.dump(jsonCode, outfile)
# JSONToFeatures requires a file as input
arcpy.JSONToFeatures_conversion(jsonFile, r'C:\NGA\Lesson 3\Geog489.gdb\Boulder_Fire_Tax_Dist', 'POLYGON')
# Clean up
if os.path.exists(jsonFile):
os.remove(jsonFile)
You can also separate the parameters into a dictionary and let requests do the url formatting, making for a cleaner code and this method seems to also format the returned date fields, if there are any:
params = {'where': '1=1', 'outFields': '*', 'f': 'pjson', 'returnGeometry': True}
response = requests.get(url, params)