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 "";

}

 

 

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