ESP8266-Arduino网络编程实例-HTTP请求JSON数据及解析

HTTP请求JSON数据及解析

在前面的文章ESP8266-Arduino网络编程实例-简单HTTP数据请求（基于Node-Red） 中，我们实现了简单的HTTP数据请求，在这里，我们将实现通过HTTP请求JSON类型数据，并对请求结果进行解析。本次实例继续使用Node-Red作为HTTP服务器。

在这里插入图片描述

在Node-Red中创建了一个流程，一个get-sensor节点，该节点响应HTTP请求，并返回JSON数据。在函数模块中添加如下代码：

1
2
3
msg.payload = {"value1":24.25, "value2":49.54, "value3":1005.14};
return msg;

流程的代码如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
[
    {
        "id": "6530621.95b429c",
        "type": "http in",
        "z": "65febd16d6c14bb0",
        "name": "",
        "url": "/get-sensor",
        "method": "get",
        "upload": false,
        "swaggerDoc": "",
        "x": 280,
        "y": 420,
        "wires": [
            [
                "9471d1a0.68588"
            ]
        ]
    },
    {
        "id": "5ddc9f47.4b555",
        "type": "http response",
        "z": "65febd16d6c14bb0",
        "name": "",
        "statusCode": "200",
        "headers": {},
        "x": 640,
        "y": 380,
        "wires": []
    },
    {
        "id": "9471d1a0.68588",
        "type": "function",
        "z": "65febd16d6c14bb0",
        "name": "",
        "func": "msg.payload = {\"value1\":24.25, \"value2\":49.54, \"value3\":1005.14};\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 470,
        "y": 429,
        "wires": [
            [
                "5ddc9f47.4b555",
                "13aea59.7430e5a"
            ]
        ]
    },
    {
        "id": "13aea59.7430e5a",
        "type": "debug",
        "z": "65febd16d6c14bb0",
        "name": "",
        "active": true,
        "tosidebar": true,
        "console": true,
        "tostatus": false,
        "complete": "payload",
        "targetType": "msg",
        "statusVal": "",
        "statusType": "auto",
        "x": 660,
        "y": 448,
        "wires": []
    }
]

在前面的文章中，我们对Arduino的JSON格式数据处理作为了详细的解析，主参考：

本次实例使用的JSON解析为Arduino_Json。

示例代码如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <WiFiClient.h>
#include <Arduino\_JSON.h>

const char\* ssid = "\*\*\*\*\*"; // WIFI名称
const char\* password = "\*\*\*\*\*"; // WIFI密码

// HTTP请求URL
const char\* serverName = "http://192.168.0.164:1880/get-sensor";


unsigned long lastTime = 0;
unsigned long timerDelay = 5000;

String sensorReadings;
float sensorReadingsArr[3];

void setup() {
  Serial.begin(115200);

  WiFi.begin(ssid, password);
  Serial.println("Connecting");
  while(WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("Connected to WiFi network with IP Address: ");
  Serial.println(WiFi.localIP());
 
  Serial.println("Timer set to 5 seconds (timerDelay variable), it will take 5 seconds before publishing the first reading.");
}

void loop() {
  // 每5秒发起一次请求
  if ((millis() - lastTime) > timerDelay) {
    // 检查WiFi状态
    if(WiFi.status()== WL_CONNECTED){
      // 请求JSON数据 
      sensorReadings = httpGETRequest(serverName);
     
      Serial.println(sensorReadings);

      // 解析JSON数据
      JSONVar myObject = JSON.parse(sensorReadings);
      if (JSON.typeof(myObject) == "undefined") {
        Serial.println("Parsing input failed!");
        return;
      }
    
      Serial.print("JSON object = ");
      Serial.println(myObject);
      JSONVar keys = myObject.keys();
    
      for (int i = 0; i < keys.length(); i++) {
        JSONVar value = myObject[keys[i]];
        Serial.print(keys[i]);
        Serial.print(" = ");
        Serial.println(value);
        sensorReadingsArr[i] = double(value);
      }
      Serial.print("1 = ");
      Serial.println(sensorReadingsArr[0]);
      Serial.print("2 = ");
      Serial.println(sensorReadingsArr[1]);
      Serial.print("3 = ");
      Serial.println(sensorReadingsArr[2]);
    }
    else {
      Serial.println("WiFi Disconnected");
    }
    lastTime = millis();
  }
}

String httpGETRequest(const char\* serverName) {
  WiFiClient client;
  HTTPClient http;
    
  // 发起HTTP请求
  http.begin(client, serverName);
  
  // 查询HTTP请求响应状态码
  int httpResponseCode = http.GET();
  
  String payload = "{}"; 
  
  if (httpResponseCode>0) {
    Serial.print("HTTP Response code: ");
    Serial.println(httpResponseCode);
    payload = http.getString();
  }
  else {
    Serial.print("Error code: ");
    Serial.println(httpResponseCode);
  }
  // 释放HTTP
  http.end();

  return payload;
}

首先，导入相关依赖头文件：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <WiFiClient.h>
#include <Arduino\_JSON.h>

const char\* ssid = "\*\*\*\*\*"; // WIFI名称
const char\* password = "\*\*\*\*\*"; // WIFI密码

// HTTP请求URL
const char\* serverName = "http://192.168.0.164:1880/get-sensor";


unsigned long lastTime = 0;
unsigned long timerDelay = 5000;

String sensorReadings;
float sensorReadingsArr[3];

接着，在setup函数中，初始化WiFi及连接：

1
2
3
4
5
6
7
WiFi.begin(ssid, password);
 Serial.println("Connecting");
 while(WiFi.status() != WL_CONNECTED) {
   delay(500);
   Serial.print(".");
 }

接着，在loop函数中，发起HTTP请求：

1
2
3
// 请求JSON数据 
sensorReadings = httpGETRequest(serverName);

其中httpGETRequest函数实现对HTTP请求进行封装：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
String httpGETRequest(const char\* serverName) {
  WiFiClient client;
  HTTPClient http;
    
  // 发起HTTP请求
  http.begin(client, serverName);
  
  // 查询HTTP请求响应状态码
  int httpResponseCode = http.GET();
  
  String payload = "{}"; 
  
  if (httpResponseCode>0) {
    Serial.print("HTTP Response code: ");
    Serial.println(httpResponseCode);
    payload = http.getString();
  }
  else {
    Serial.print("Error code: ");
    Serial.println(httpResponseCode);
  }
  // 释放HTTP
  http.end();

  return payload;
}

在请求完成之后，对服务响应数据进行解析：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
// 解析JSON数据
      JSONVar myObject = JSON.parse(sensorReadings);
      if (JSON.typeof(myObject) == "undefined") {
        Serial.println("Parsing input failed!");
        return;
      }
    
      Serial.print("JSON object = ");
      Serial.println(myObject);
      JSONVar keys = myObject.keys();
    
      for (int i = 0; i < keys.length(); i++) {
        JSONVar value = myObject[keys[i]];
        Serial.print(keys[i]);
        Serial.print(" = ");
        Serial.println(value);
        sensorReadingsArr[i] = double(value);
      }
      Serial.print("1 = ");
      Serial.println(sensorReadingsArr[0]);
      Serial.print("2 = ");
      Serial.println(sensorReadingsArr[1]);
      Serial.print("3 = ");
      Serial.println(sensorReadingsArr[2]);

运行结果如下：

在这里插入图片描述

文章来源: https://iotsmart.blog.csdn.net/article/details/127179606