上一节我们讲了如何通过vue uniapp还有web3以及需要准备的相关组件，来搭建了DAPP开发的环境。

这一节，我们来说说如何用代码来实现DAPP相关接口。

1. ethers实现类 

导入组件

import { ethers , providers , utils  } from "ethers";
import tokenABI from '@/utils/tokenABI.json'
export class MetaEthers {}

初始化

static #provider = null ;
static #account = null ;
static #message = 'sign message'
static #max = '0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff'
constructor(){
    check();
    if(!MetaEthers.#provider)MetaEthers.#provider = new ethers.providers.Web3Provider(window.ethereum);
} 
function check(target){
     if(typeof window.ethereum == 'undefined')
   throw uni.showToast({title: "MetaMask is unInstalled!", icon: "none"})
}

获取钱包地址

// 获取钱包地址
  async setAccounts(){
      let account = await MetaEthers.#provider.send("eth_requestAccounts", []);
      MetaEthers.#account =  account instanceof Array ? account[0] : account;
      let info = JSON.parse(localStorage.getItem('userinfo'))
      if( info && MetaEthers.#account.toLowerCase() !== info.chain_address){
          this.destory()
          throw t('dismacth');
      } else{
          return MetaEthers.#account;
      }     
  }

签名获取

// 签名
async sign(){
    if(!MetaEthers.#account) throw { reason: t('wallet_warning'), errType: -1 }
    const signer = MetaEthers.#provider.getSigner();
    let signature = await signer.signMessage(MetaEthers.#message)
    console.log( utils.verifyMessage(MetaEthers.#message, signature).toLowerCase() )
    return signature;
}

余额获取

// 钱包余额
async getWallet(){
    if(!MetaEthers.#account) throw { reason: t('wallet_warning'), errType: -1 }
    let Contract = new ethers.Contract(
        tokenAddress,
        tokenABI,
        MetaEthers.#provider.getSigner()
    );
    let value = await Contract.balanceOf(MetaEthers.#account);
    return ethers.utils.formatUnits(value, 18)
}

2. 实现签名登录

import {
  MetaEthers
} from '@/utils/metamask.js'

let MetaWallet = {
  destory: () => {}
};

// 通过实现类，获取地址及签名，后端进行验证
let chain_address = await MetaWallet.setAccounts();
let signature = await MetaWallet.sign();
const {
  data,
  code
} = await walletLogin({
  method: "POST",
  query: {
    chain_address,
    message: MetaEthers.getMessage(),
    signature,
  },
});

后端实现

/**
 * <b>功能描述：</b>验签<br>
 * <b>修订记录：</b><br>
 */
public static Boolean isSignatureValid(final String address, final String signature, final String message) {
    log.info("isSignatureValid invoked for Address {} with Signature {} and Message {} ", address, signature, message);
    final String personalMessagePrefix = "\u0019Ethereum Signed Message:\n";
    boolean match = false;

    final String prefix = personalMessagePrefix + message.length();
    final byte[] msgHash = Hash.sha3((prefix + message).getBytes());
    final byte[] signatureBytes = Numeric.hexStringToByteArray(signature);
    byte v = signatureBytes[64];
    if (v < 27) {
        v += 27;
    }
    final Sign.SignatureData sd = new Sign.SignatureData(v,
            Arrays.copyOfRange(signatureBytes, 0, 32),
            Arrays.copyOfRange(signatureBytes, 32, 64));
    String addressRecovered = null;
    // Iterate for each possible key to recover
    for (int i = 0; i < 4; i++) {
        final BigInteger publicKey = Sign.recoverFromSignature((byte) i, new ECDSASignature(
                new BigInteger(1, sd.getR()),
                new BigInteger(1, sd.getS())), msgHash);

        if (publicKey != null) {
            addressRecovered = "0x" + Keys.getAddress(publicKey);
            if (addressRecovered.equalsIgnoreCase(address)) {
                match = true;
                break;
            }
        }
    }
    return match;
}

当验签成功后，即实现登录，接下来基本都业务相关代码，自行开发吧！！！