Node-RED で、JSON ファイルを読む

Node-RED で、JSON ファイルを読む方法

１）次の ５つの node を配置する
　"http in" "file" "json" "function" "http response"

２）"http in"
URL を /json にする

３）"file"
ファイル名を入れる　例：/var/tmp/json/cities.json

４）"json"
デフォールトのまま

５）"function"

var dict_aa = msg.payload
var str_out = "<table>"
for (var key in dict_aa)
{
     str_out += "<tr>"
     str_out += "<td>" + key + "</td>"
     str_out += "<td>" + dict_aa[key].name + "</td>"
     str_out += "<td>" + dict_aa[key].population + "</td>"
     str_out += "<td>" + dict_aa[key].date_mod + "</td>"
     str_out += "</tr>"
}
str_out += "</table>"
msg.payload = str_out
return msg;

６）"http response"
デフォールトのまま

７）node を結んでデプロイする

８）ブラウザーで http://127.0.0.1:1880/json にアクセスする

入力に使った JSON ファイル

cities.json

{
 "t0921":
 {"name": "宇都宮",
 "population": 84516,
 "date_mod": "2001-3-16"}
,
 "t0922":
 {"name": "小山",
 "population": 91237,
 "date_mod": "2001-4-21"}
,
 "t0923":
 {"name": "佐野",
 "population": 63489,
 "date_mod": "2001-5-21"}
,
 "t0924":
 {"name": "足利",
 "population": 72561,
 "date_mod": "2001-6-23"}
,
 "t0925":
 {"name": "日光",
 "population": 61743,
 "date_mod": "2001-9-21"}
,
 "t0926":
 {"name": "下野",
 "population": 52398,
 "date_mod": "2001-8-14"}
,
 "t0927":
 {"name": "さくら",
 "population": 45182,
 "date_mod": "2001-7-05"}
,
 "t0928":
 {"name": "矢板",
 "population": 37617,
 "date_mod": "2001-10-14"}
,
 "t0929":
 {"name": "真岡",
 "population": 52698,
 "date_mod": "2001-9-19"}
,
 "t0930":
 {"name": "栃木",
 "population": 47912,
 "date_mod": "2001-11-23"}
,
 "t0931":
 {"name": "大田原",
 "population": 52317,
 "date_mod": "2001-9-22"}
,
 "t0932":
 {"name": "鹿沼",
 "population": 62158,
 "date_mod": "2001-8-25"}
,
 "t0933":
 {"name": "那須塩原",
 "population": 82719,
 "date_mod": "2001-6-27"}
,
 "t0934":
 {"name": "那須烏山",
 "population": 38157,
 "date_mod": "2001-5-14"}
}