適用於ESP32 server應用的HttpRequestString類別

最近在測試ESP32，他的SimepleWiFiServer範例直接使用WiFiServer類別建立server，ESP8266則直接提供WebServer類別，server.on()函數可以根據url後面的字串自動呼叫處理函數，這功能在ESP32目前尚無法使用，因此撰寫了 HttpRequestString 類別，用來支援參數分析，只要將GET後面的字串帶入，就可得到 Uri與參數的Name-Value。該類別使用了 String 類別，WString.h是ESP32提供的，如果用於其他Core須自行修改，例如 #include <String.h>。

以下getClientRequest()，是參考ESP32的DNS_Web_Server的範例，當 client連線時，取的GET後面的request字串：

String getClientRequest(WiFiClient client) {     // Wait for data from client to become available     while(client.connected() && !client.available()){         delay(1);     }     // Read the first line of HTTP request     String request = client.readStringUntil('\r');     // First line of HTTP request looks like "GET /path HTTP/1.1"     // Retrieve the "/path" part by finding the spaces     int addr_start = request.indexOf(' ');     int addr_end = request.indexOf(' ', addr_start + 1);     if (addr_start == -1 || addr_end == -1) {         Serial.print("Invalid request: ");         Serial.println(request);         return "";     }     request = request.substring(addr_start + 1, addr_end);     Serial.print("Request: ");     Serial.println(request);     client.flush();     return request; }

將上面取得的request字串傳入responseClientRequest()，建立params物件後，即可取得request的uri與參數的值，接著可用於response判斷。

void responseClientRequest(WiFiClient client, String request) {     HttpRequestParams params(request);         if (params.Uri == "/")     {         sendHeader(client);         //if (params.get("Level").length()>0)         {             client.print("Level is '");             client.print(params.get("Level"));             client.print("'<br>");         }         sendBody(client);         sendTail(client);     }     // Check to see if the client request was "GET /H" or "GET /L":     else if (params.Uri=="/H") {         LedStatus = HIGH;         digitalWrite(pinLED, LedStatus);               // GET /H turns the LED on         Serial.println("LED ON");         sendPage(client);     }     else if (params.Uri=="/L") {          LedStatus = LOW;          digitalWrite(pinLED, LedStatus);                // GET /L turns the LED off          Serial.println("LED OFF");          sendPage(client);     }     else {         sendHeader(client);         client.print("HTTP/1.1 404 Not Found\r\n\r\n");         sendTail(client);     }         // close the connection:     client.stop();     Serial.println("client disonnected"); }

以下是類別HttpRequestString.h:

// HttpRequestString.h #ifndef HttpRequestString_h #define HttpRequestString_h #include <WString.h> #define MaxParamaterCount 10 typedef struct {     String Name;     String Value;  } HttpRequestParam; class HttpRequestParams {    public:            String Uri;         HttpRequestParam param[MaxParamaterCount];         int paramCount;                 HttpRequestParams(String request);         String get(String Name); }; #endif //HttpRequestString_h //

以下是實做檔HttpRequestString.cpp:

// HttpRequestString.cpp #include <Arduino.h> #include "HttpRequestParams.h" #define DEBUG_LEVEL   0 HttpRequestParams::HttpRequestParams(String request) {        paramCount = 0;         int param_start = request.indexOf('?');      #if (DEBUG_LEVEL>0)     Serial.print("param_start=");     Serial.println(param_start);     #endif     if (param_start<0) {              Uri = request;         return; //no parameters     } else {         Uri = request.substring(0, param_start-1);     }     #if (DEBUG_LEVEL>0)     Serial.print("Uri=");     Serial.println(Uri);     #endif     int param_separator = request.indexOf('=', param_start + 1);     #if (DEBUG_LEVEL>0)     Serial.print("param_separator=");     Serial.println(param_separator);     #endif      while (param_separator > 0) { //found a parameter             param[paramCount].Name = request.substring(param_start + 1, param_separator);         int param_end = request.indexOf('&', param_start + 1);         if (param_end<0) param_end = request.length(); //last parameter         param[paramCount].Value = request.substring(param_separator + 1, param_end);                 #if (DEBUG_LEVEL>0)         Serial.print("Param(");         Serial.print(paramCount);         Serial.print("): ");         Serial.print(param[paramCount].Name);         Serial.print("=");         Serial.println(param[paramCount].Value);         #endif         paramCount++;         param_start = param_end;         param_separator = request.indexOf('=', param_start + 1);     } } String HttpRequestParams::get(String Name) {     #if (DEBUG_LEVEL>1)     Serial.print("Search ");     Serial.print(Name);     #endif          for (int i=0; i<paramCount; i++) {         #if (DEBUG_LEVEL>1)         Serial.print(" ");         Serial.print(i);         #endif         if (param[i].Name.equals(Name)) {             #if (DEBUG_LEVEL>1)             Serial.print(" Found ");             Serial.println(param[i].Value);             #endif             return param[i].Value;         }     }     #if (DEBUG_LEVEL>1)     Serial.println();     #endif     return ""; }