我如何将 dapp 连接到数据库（mysql）

Question

I'm making an Ethereum-based voting app app app dapp. It is using truffle and uses virtual accounts through meta-mask. I don't know what to do if I want to put the record in the database when I vote. I want to use mysql for the database.

OS: ubuntu 18.07

truffle: 5.0

nvm: 0.33.1

nodejs:12.14.1

npm: 6.13.4

contracts/ election.sol:

*pragma solidity ^0.5.0; contract Election {

// 후보자 모델
struct Candidate {
   
uint id;
string name;
uint votefirst;     //1순위투표수
uint voteSeond;     //2순위투표수
uint votethird;     //3순위투표수
uint voteCount;     //전체 유권자들이 투표한 총 투표수 

}

// 후보자 기호 변수
uint public candidatesCount; //후보자수 
uint public voteCount;  //총 투표수 
string public votename; 
uint public voterCount; //투표자수  
uint public test = 0;

// 후보자 반환하기
mapping(uint => Candidate) public candidates;


// 투표에 참여한 ID 기록
mapping(address => bool) public voters;


// 후보자 등록하기
function addCandidate (string memory _name) public {
    candidatesCount++;
    candidates[candidatesCount] = Candidate(candidatesCount, _name, 0 , 0, 0, 0);
}



// constructor
constructor() public {
    addCandidate('A');
    addCandidate('B');
    addCandidate('C'); 
//voterCount++;


}

// 투표하기
function vote(uint _candidateId) public {
    
    // 중복투표를 하면 오류를 발생 시킨다.
   //require(!voters[msg.sender]);
    // 목록에 없는 후보자에게 투표하면 오류를 발생시킨다.
 require(_candidateId > 0 && _candidateId <= candidatesCount);
    // 투표에 참여한 ID를 기록해서 두번 투표하지 못하도록 한다.
     voters[msg.sender] = true;
    // 득표수를 +1 한다.
    candidates[_candidateId].votefirst = candidates[_candidateId].votefirst+1;
candidates[_candidateId].votefirst = candidates[_candidateId].votefirst+test;
candidates[_candidateId].voteCount = candidates[_candidateId].voteCount+3;

}
function vote1(uint _candidateId) public {
    
    // 중복투표를 하면 오류를 발생 시킨다.
    //require(!voters[msg.sender]);
    // 목록에 없는 후보자에게 투표하면 오류를 발생시킨다.
    require(_candidateId > 0 && _candidateId <= candidatesCount);
    // 투표에 참여한 ID를 기록해서 두번 투표하지 못하도록 한다.
    voters[msg.sender] = true;
    // 득표수를 +1 한다.
    candidates[_candidateId].voteSeond = candidates[_candidateId].voteSeond +1 ;
    candidates[_candidateId].voteCount = candidates[_candidateId].voteCount+3;
    //votelist[voterCount].vote_s=candidates[_candidateId].voteSeond;
}
function vote2(uint _candidateId) public {
    
    // 중복투표를 하면 오류를 발생 시킨다.
    //require(!voters[msg.sender]);
    // 목록에 없는 후보자에게 투표하면 오류를 발생시킨다.
    require(_candidateId > 0 && _candidateId <= candidatesCount);
    // 투표에 참여한 ID를 기록해서 두번 투표하지 못하도록 한다.
     voters[msg.sender] = true;
    // 득표수를 +1 한다.
   
   candidates[_candidateId].votethird = candidates[_candidateId].votethird +1 ;
   candidates[_candidateId].voteCount = candidates[_candidateId].voteCount+3;
 //votelist[voterCount].vote_t=candidates[_candidateId].votethird;
}

}*

src/js/app.js:

      var App = {
          web3Provider: null,
          contracts: {}
      }

      $(window).load(function () {

// web3Provider 생성하기
if (typeof web3 !== 'undefined') {
    // MetaMask가 설치되어 있어서 web3 인스턴스가 이미 생성되어 있음
    App.web3Provider = web3.currentProvider;
    web3 = new Web3(web3.currentProvider);
} else {
    // MetaMask가 설치되지 않았을 경우 기본 인스턴스를 지정함
    App.web3Provider = new Web3.providers.HttpProvider('http://localhost:7545');
    web3 = new Web3(App.web3Provider);
}

// Election.json을 가지고 온다.
$.getJSON('Election.json', function (election) {
    // Truffle 계약을 초기화 함
    App.contracts.Election = TruffleContract(election);
    // 인스턴스에 접속함
    App.contracts.Election.setProvider(App.web3Provider);

    render();
});

            var voter =0;
            var vote_winner;
            var account_mine;
            var vote_num;

// 화면구현
function render() {

    // 계정 정보 읽어오기
    web3.eth.getCoinbase(function (err, account) {
        if (err === null) {
            App.account = account;
            $('#accountAddress').html('나의 계정: ' + account);
        }
    });

    // 계약 정보를 읽어온다.
    App.contracts.Election.deployed().then(function (instance) {
        electionInstance = instance;
        return electionInstance.candidatesCount();
    }).then(function (candidatesCount) {
        for (var i = 1; i <= candidatesCount; i++) {
            electionInstance.candidates(i).then(function (candidate) {
            var id = candidate[0];
            var name = candidate[1];
            var voteCount1 = candidate[2];
            var voteCount2 = candidate[3];      
            var voteCount3 = candidate[4];
            var voteCountall = candidate[5];
            var name1 = candidate[6] + account_mine;
            var voteAccount = account_mine;
            var voteSum= (parseInt(voteCount1) + (parseInt(voteCount2)*2) + (parseInt(voteCount3)*3));
         
            voter = voteCountall;

                // 투표결과 html 파싱
              var candidateTemplate = '<tr><th>' + id + '</th><td>' + name + '</td><td>' + voteCount1 + '</td><td>' + voteCount2 + '</td><td>' + voteCount3 + '</td></tr>'
              $('#candidatesResults').append(candidateTemplate);

     
             if( (voter / 3) / 2 <  voteCount1)
    { 
      vote_winner = name;
      var candidateTemplate1 = '<tr><th>' + id + '</th><td>' + name + '</td></tr>'
              $('#candidatesResults1').append(candidateTemplate1);
    }



      var candidateOption_first = '<option value="' + id + '">' + name + '</option>'
              $('#candidateSelect1').append(candidateOption_first);

      var candidateOption_second = '<option value="' + id + '">' + name + '</option>'
              $('#candidateSelect2').append(candidateOption_second);

      var candidateOption_third = '<option value="' + id + '">' + name + '</option>'
              $('#candidateSelect3').append(candidateOption_third);

            });
        }

        // 후보자 화면 표시
        $('#loader').hide();
        $('#content').show();
    }).catch(function (error) {
        console.warn(error);
    });
}



      $('#btnVote').on('click', function() {




    
    var candidateId_first = $('#candidateSelect1').val()
var candidateId_second = $('#candidateSelect2').val()
var candidateId_third = $('#candidateSelect3').val()



vote_1 = candidateId_first;
vote_2 = candidateId_second;
vote_3 = candidateId_third;


  if ((!candidateId_first) || ( !candidateId_second ) || ( !candidateId_third) ) {
      return alert('모든 후보자의 순위를 선택해주세요.')
  }

  if ((candidateId_first == candidateId_second) || (candidateId_second == candidateId_third) || (candidateId_third == candidateId_first)){
      return alert('순위별 후보자가 중복되었습니다.')
  }


    

  App.contracts.Election.deployed()
      .then(function(instance) {
          return instance.vote(candidateId_first, {from: App.account}),
                 instance.vote1(candidateId_second, {from: App.account}),
                 instance.vote2(candidateId_third, {from: App.account})
    })
      
      .then(function(result) {
          if (result.receipt) {
        
                vote_num++;
                var j= parseInt(voter);
                voter =j+3;
                alert('성공적으로 투표했습니다.')
                location.reload();
          }
    })
      .catch(function(error) {
          alert(error.message)
          alert('투표하실 수 없습니다.')
    })



});

});

src/index.html:

      <!DOCTYPE html>
      <html lang="en">
      <head>
       <meta charset="utf-8">
          <meta http-equiv="X-UA-Compatible" content="IE=edge">
          <meta name="viewport" content="width=device-width, initial-scale=1">
          <title>투표 결과</title>
      </head>
      <body>
       <h1>투표 결과</h1>

       <!-- 로딩바 -->
          <div id="loader">
             <p>로딩중...</p>
          </div>
      
          <div id="content" style="display: none;">

    <!-- 투표결과 표시 -->
    <table class="table" style="width: 50%">
        <colgroup>
            <col width="200">
            <col width="*">
            <col width="100">
        </colgroup>
        <thead>
            <tr>
        
                <th scope="col">기호</th>
                <th scope="col">이름</th>
                <th scope="col">1순위 득표수</th>
       <th scope="col">2순위 득표수</th>
         <th scope="col">3순위 득표수</th>

            </tr>
        </thead>
        <tbody id="candidatesResults">
    
    
        </tbody>
    </table>
<table>
 <thead>
            <tr>
        
                <!-- <th >득표수</th> -->

            </tr>
        </thead>
        <tbody id="voteCount">
        </tbody>
    </table>





    <h2>투표 참여</h2>


<table class="table" style="width: 100%">
        <colgroup>
            <col width="60">
            <col width="*">
            <col width="100">
        </colgroup>

    <thead>
            <tr>
                <th scope="col">순위</th>
                <th scope="col">이름</th>
                
            </tr>
        </thead>
        <thead>
            <tr>
                <th scope="col">1</th>
                <th scope="col">
            <select id="candidateSelect1">
                        <option value="">후보자를 선택하세요.</option>
                 </select>
        </th>
                
            </tr>
        </thead>
    
   <thead>
            <tr>
                <th scope="col">2</th>
                <th scope="col">
            <select id="candidateSelect2">
                        <option value="">후보자를 선택하세요.</option>
                 </select>
        </th>
                
            </tr>
        </thead>



    <thead>
            <tr>
                <th scope="col">3</th>
                <th scope="col">
            <select id="candidateSelect3">
                        <option value="">후보자를 선택하세요.</option>
                 </select>

               
        
            </tr>
        </thead>

    
</table>
     <button id="btnVote">투표하기</button>





<table>
<thead>
<colgroup>
            <col width="200">
            <col width="*">
            <col width="100">
        </colgroup>
  <tr>
        
                 <th scope="col">투표자 기록</th>
                 <th scope="col">   이름</th>

            </tr>
 </thead>

   
        
    
    <tbody id="candidatesResults1">
    <p id="accountAddress"></p>
        </tbody>
    </table>
    
 

</div>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script src="js/web3.min.js"></script>
<script src="js/truffle-contract.js"></script>
<script src="js/app.js"></script>

please let me know how to solve this problem..

Answer 1

By the definition, dApps do not connect databases, but they connect to a blockchain. So your question makes little sense.

The best way to get data from a blockchain to a database is to have a server-side process that connects to Ethereum node, listens for Solidity events and then copies and writes those events to your internal SQL database.