Node Red 에서 장치의 json, xml 형식의 데이터를 처리하는 방법

前言

在使用node-red处理各种业务场景时，我们时常会遇到各种各样的数据格式，最常见的是json数据格式，其次还有xml，yaml，以及csv格式的数据格式。这些都是需要我们对其数据格式有一点解析和转化的能力，今天这篇文章我就来教大家如何处理json 和 xml数据格式。

node-red中json格式的转换

在node-red中处理json数据格式是最简单的。最主要的原因是node-red本身就是使用javascript语言来编写的。而javascript中最常用的就是json数据格式。声明一个json数据格式很简单。

# json 数据的声明
const person = {name: 'fizzz', age:12}
# 打印数据
console.log(person.name)
# 重新赋值
person.name = 'tom'

json 数据格式的操作就是这样的简单。

下面是一个json转换的流，大家可以从这个流中体验的对json数据的操作。

[{"id":"634256b7.2d6818","type":"inject","z":"64133d39.bb0394","name":"JSON String","topic":"","payload":"{"a":1}","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":110,"y":80,"wires":[["a2fe0fc8.095e1"]]},{"id":"a2fe0fc8.095e1","type":"json","z":"64133d39.bb0394","name":"","property":"payload","action":"","pretty":false,"x":270,"y":80,"wires":[["9a4ce2b8.47698"]]},{"id":"9a4ce2b8.47698","type":"debug","z":"64133d39.bb0394","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":430,"y":80,"wires":[]},{"id":"80032e2.7c92cd","type":"inject","z":"64133d39.bb0394","name":"Object","topic":"","payload":"{"a":1}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":90,"y":120,"wires":[["cd40a0f4.4f5ac"]]},{"id":"cd40a0f4.4f5ac","type":"json","z":"64133d39.bb0394","name":"","property":"payload","action":"","pretty":false,"x":270,"y":120,"wires":[["478b4106.4fd7c"]]},{"id":"478b4106.4fd7c","type":"debug","z":"64133d39.bb0394","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":430,"y":120,"wires":[]}]

效果图如下：

json 数据的处理主要是借助来json核心节点，它可以将字符串与json数据互转。 非常方便。如果转换失败就会报错。
json 节点的详细配置如下：

输入参数：
payload：object | 字符串
JavaScript对象或JSON字符串。
schema：object
可选的JSON Schema对象用于验证有效负载。在将msg发送到下一个节点之前，将删除该属性。

输出参数：
payload：object | 字符串
如果输入是JSON字符串，它将尝试将其解析为JavaScript对象。
如果输入是JavaScript对象，它将创建一个JSON字符串。并可以选择对此JSON字符串进行整形。
schema：오답数组
如果JSON模式验证失败，则catch节点将具有包含错误数组的schema오답属性。

node-red中处理 xml格式的数据

在ndoe-red中处理xml的数据，主要场景是 json数据转换为xml数据，或者xml格式的数据转换为json数据格式。其中主要借助的是xml核心节点，其底层是使用了xml2json这个库。

xml这个节点的需要的输入有二个参数

payload ： object | 字符串
设置为JavaScript对象或XML字符串。

options：object
可以将选项传递给内部使用的XML转换库。请参见 xml2js文档 来获取更多信息。

输出结果是
payload : object | 字符串
如果输入是字符串，它将尝试将其解析为XML并创建一个JavaScript对象。
如果输入是JavaScript对象，它将尝试构建XML字符串。

另外在XML和对象之间进行转换时，默认情况下XML属性会添加到名为$的属性中。将文本内容添加到名为_的属性中。这些属性名称可以在节点设置中更改。

下面是一个例子，大家可以从这个例子感受到node-red对xml数据与json数据格式的转换

[{"id":"1b546d47.9474e3","type":"inject","z":"64133d39.bb0394","name":"XML String","topic":"","payload":"{"a":1}","payloadType":"str","repeat":"","crontab"]]:"once ": false,"once D elay ": 0. 1," x ": 100," y ": 26 0," wir es ":"d 72 b 2 b f d. 77 d 0 68"]]},{"id ":" 1 ad f 40 7 d. 6 c 4 fe "," type ":"de bug "," z ":" 64 13 3 d 39. bb 0 39 4 "," name ":"once ": true," tos id ebar ": true,"con active ": false," t ost atus ": false,"com ple te ": false "," x ": 59 0," y ": 26 0," wir es ":},{" id":" 46 6 38 89 0. 8 ae 75 8 "," type ":" in ject"," z":" 64 13 3 d 39. bb 0 39 4"," name":" Ob ject"," top ic":" Pay load":"{" note":{"$":{" pri or ity":" high "}," to":" N ick ")," fr om":" Da ve"," he ading":" R em inder"," body":" Web site 업데이트]}}," pay load Ty pe":" j son"," re pe at":" cron tab":" once": false," once D elay": 0. 1," x": 90," y": 300," wir es ":" dae 1 d 29 1. de 0 d 2"]]},{" id":" 6 fe f ca 6 7. 36 69 e 4 "," type":" de bug "," z":" 64 13 3 d 39. bb 0 39 4 "," name":"" active ": true," tos id ebar ": true," con sole ": false," t ost atus ": false," com ple te ": false "," x": 430," y": 300," wir es ":]},{" id":" d 72 b 2 b f d. 77 d 0 68 "," type":" template pay z":" 64 13 3 d 39. bb 0 39 4 "," type" name":" load field "," type":" ms g "," syn tax: " text: " format"" pla in "," temp late":" note priority =" high" n to Nick/to n from Dave/from n heading Rem inder/heading n body 웹 사이트/body n/note 업데이트 "," out put":" str"," x": 28 0," y": 26 0," wir es":" 17 46[[ 464 a. 87 aa 4 a "]]}, {" id ":" 17464 a. 87 aa 4 a "," type ":" xml "," z ":" 64133 d 39. bb 0394 "," name ":" ", "property ":" payload "," attr ":" ", "chr ":" ", "x ":" 430, "y ":" 260, "wires ":" 1 adf 407 d. 6 c 4 fe "]]}, {" id ":"dae 1 d 291. de 0 d 2 "," type ":" xml "," z ":" 64133 d 39. "", " 0394 ", "name ":":":":" payload ", "attr ":" ", "chr ":" x "0, "y ":" 300", wires " 6 fca 67. 36 69 e "]]}][[[[[[[[<><><><><><><><><><>[[[[[[

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