1.准备jar包

        <dependency>
            <groupId>com.github.wechatpay-apiv3</groupId>
            <artifactId>wechatpay-java</artifactId>
            <version>0.2.6</version>
        </dependency>

2.配置yaml

# 微信小程序支付配置信息
wechat:
  pay:
    # 微信小程序appid
    app-id: xxx
    # 商户号
    mch-id: xxxx
    # 证书序列号
    mch-serial-no: xxxx
    # 小程序密钥
    app-secret: xxxxx
    # api密钥
    api-key: xxxxxx
    # 回调接口地址
    notify-url: xxxx
    # 证书地址
    key-path: xxxxxxx

3.配置config

3.1: 参数信息

@Component
@ConfigurationProperties(prefix = "wechat.pay")
@Data
public class WxPayV3Bean {
    
    private String appId;          // 小程序appid
    private String mchId;          // 商户号
    private String notifyUrl;      // 支付回调地址
    private String tradeType = "JSAPI"; // 交易类型
    //证书序列号
    private String mchSerialNo;
    //小程序密钥
    private String appSecret;
    //商户API私钥
    private String apiKey;
    //商户API证书
    private String keyPath;



}

3.2: 单例config

@Configuration
public class wxConfig {

    @Resource
    private WxPayV3Bean wxPayV3Bean;

    @Bean
    public Config getConfig(){
        // 一个商户号只能初始化一个配置，否则会因为重复的下载任务报错
        return new RSAAutoCertificateConfig.Builder()
                .merchantId(wxPayV3Bean.getMchId())
                .privateKeyFromPath(wxPayV3Bean.getKeyPath())
                .merchantSerialNumber(wxPayV3Bean.getMchSerialNo())
                .apiV3Key(wxPayV3Bean.getApiKey())
                .build();
    }

}

4.写个微信支付的工具类

        好多方法里面都是自己封装的vo，根据自己的要求来

@Component
@Slf4j
public class WXPayUtil {

    private static final String SYMBOLS = "0123456789abcdefghijklmnopqrstuvwxyz";

    private static final Random RANDOM = new SecureRandom();
    @Resource
    private WxPayV3Bean wxPayV3Bean;
    @Resource
    private Config config;


    public String getSign(String signatureStr, String privateKey) throws InvalidKeyException, NoSuchAlgorithmException, SignatureException,
            IOException, URISyntaxException {
        //replace 根据实际情况，不一定都需要
        String replace = privateKey.replace("\\n", "\n");
        PrivateKey merchantPrivateKey = PemUtil.loadPrivateKeyFromPath(replace);
        Signature sign = Signature.getInstance("SHA256withRSA");
        sign.initSign(merchantPrivateKey);
        sign.update(signatureStr.getBytes(StandardCharsets.UTF_8));
        return Base64Utils.encodeToString(sign.sign());
    }

    /**
     * 获取随机字符串 Nonce Str
     *
     * @return String 随机字符串
     */
    public static String generateNonceStr(String prefix) {
        char[] nonceChars = new char[32];
        for (int index = 0; index < nonceChars.length; ++index) {
            nonceChars[index] = SYMBOLS.charAt(RANDOM.nextInt(SYMBOLS.length()));
        }
        return prefix + new String(nonceChars);
    }

    /**
     * 获取微信支付参数
     *
     * @param req
     * @param openId
     * @return
     */
    public WxPayRespVO getWxPayRespVO(ApplyForTransferDO req, String openId) {
        // request.setXxx(val)设置所需参数，具体参数可见Request定义
        PrepayRequest request = new PrepayRequest();
        Amount amount = new Amount();                amount.setTotal(req.getAmountPayable().multiply(BigDecimal.valueOf(100)).intValue());
        amount.setTotal(1);
        request.setAmount(amount);
        request.setAppid(wxPayV3Bean.getAppId());
        request.setMchid(wxPayV3Bean.getMchId());
        request.setDescription("xxxx");
        request.setNotifyUrl(wxPayV3Bean.getNotifyUrl());
        request.setOutTradeNo(req.getOrderNo());
        request.setAttach(req.getPaymentMethod());
        Payer payer = new Payer();
        payer.setOpenid(openId);
        request.setPayer(payer);
        // 调用下单方法，得到应答
        JsapiService service = new JsapiService.Builder().config(config).build();
        PrepayResponse response = service.prepay(request);

        WxPayRespVO vo = new WxPayRespVO();
        Long timeStamp = System.currentTimeMillis() / 1000;
        vo.setTimeStamp(timeStamp);
        String substring = UUID.randomUUID().toString().replaceAll("-", "").substring(0, 32);
        vo.setNonceStr(substring);
        String signatureStr = Stream.of(wxPayV3Bean.getAppId(), String.valueOf(timeStamp), substring, "prepay_id=" + response.getPrepayId())
                .collect(Collectors.joining("\n", "", "\n"));
        String sign = getSign(signatureStr, wxPayV3Bean.getKeyPath());
        vo.setPaySign(sign);
        vo.setPrepayId(response.getPrepayId());
        return vo;

    }

    /**
     * 回调
     *
     * @param request
     */
    public void callback(HttpServletRequest request) {
        try {
            //读取请求体的信息
            ServletInputStream inputStream = request.getInputStream();
            StringBuffer stringBuffer = new StringBuffer();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
            String s;
            //读取回调请求体
            while ((s = bufferedReader.readLine()) != null) {
                stringBuffer.append(s);
            }
            String s1 = stringBuffer.toString();
            String timestamp = request.getHeader(WECHAT_PAY_TIMESTAMP);
            String nonce = request.getHeader(WECHAT_PAY_NONCE);
            String signType = request.getHeader("Wechatpay-Signature-Type");
            String serialNo = request.getHeader(WECHAT_PAY_SERIAL);
            String signature = request.getHeader(WECHAT_PAY_SIGNATURE);
            NotificationParser parser = new NotificationParser((NotificationConfig) config);
            // 验签、解密并转换成 Transaction
            RequestParam requestParam = new RequestParam.Builder()
                    .serialNumber(serialNo)
                    .nonce(nonce)
                    .signature(signature)
                    .timestamp(timestamp)
                    // 若未设置signType，默认值为 WECHATPAY2-SHA256-RSA2048
                    .signType(signType)
                    .body(s1)
                    .build();
            Transaction parse = parser.parse(requestParam, Transaction.class);
            System.out.println("parse = " + parse);
        } catch (Exception e) {
            log.error("微信支付回调异常，" + e.getMessage());
        }
    }

    /**
     * 查询状态
     * @param transferDO
     * @return
     */
    public Object findOrderStatus(ApplyForTransferDO transferDO) {
        QueryOrderByOutTradeNoRequest  queryRequest = new QueryOrderByOutTradeNoRequest ();
        queryRequest.setMchid(wxPayV3Bean.getMchId());
        queryRequest.setOutTradeNo(transferDO.getOrderNo());
        try {
            JsapiServiceExtension service =
                    new JsapiServiceExtension.Builder()
                            .config(config)
                            .signType("RSA")
                            .build();
            Transaction result = service.queryOrderByOutTradeNo(queryRequest);
            if (Transaction.TradeStateEnum.SUCCESS.equals(result.getTradeState())) {
                return true;
            }
        } catch (ServiceException e) {
            log.error("订单查询失败，返回码：{},返回信息：{}");
        }
        return false;

    }

5.封装的实体类

        别的就不提供了，差不多自己定义

@Data
@Accessors(chain = true)
public class WxPayRespVO implements Serializable {
 
    private static final long serialVersionUID = 1L;
    /**
     * 预支付交易会话标识小程序下单接口返回的prepay_id参数值
     */
    private String prepayId;
    /**
     * 随机字符串
     */
    private String nonceStr;
    /**
     * 时间戳
     */
    private Long timeStamp;
    /**
     * 签名
     */
    private String paySign;
}