依赖

<dependency>
  <groupId>com.github.wechatpay-apiv3</groupId>
  <artifactId>wechatpay-java</artifactId>
  <version>0.2.14</version>
</dependency>

配置类

import com.wechat.pay.java.core.cipher.SignatureResult;
import com.wechat.pay.java.core.notification.Notification;
import com.wechat.pay.java.core.notification.NotificationParser;
import com.wechat.pay.java.core.notification.RequestParam;
import com.wechat.pay.java.service.payments.model.Transaction;
import com.wechat.pay.java.service.payments.jsapi.JsapiService;
import com.wechat.pay.java.service.payments.jsapi.model.*;
import com.wechat.pay.java.service.payments.model.TransactionAmount;
import com.wechat.pay.java.service.refund.RefundService;
import com.wechat.pay.java.service.refund.model.AmountReq;
import com.wechat.pay.java.service.refund.model.CreateRequest;
import com.wechat.pay.java.service.refund.model.Refund;
import com.wechat.pay.java.service.refund.model.ReqFundsAccount;



@Configuration
@Setter
@Getter
@ConfigurationProperties("wxmini")
@Slf4j
public class WxMiniConfiguration {

    /** 商户号 */
    private  String mchid;
    /** 小程序appid */
    private  String appid; 
    /** 支付回调 */
    private  String notifyUrl;
    /** 商户证书序列号 */
    private  String serialNumber;

    /** 商户API私钥路径 */
    private  String privateKeyPath;
    /** 商户APIV3密钥 */
    private  String payApiV3Key;

    private RSAAutoCertificateConfig config;


    public WxMiniConfiguration(){

    }

    private void createConfig(){
        try {
            File file = new File(this.privateKeyPath);
            if (!file.exists()) {//如果配置不存在
                try {
                    String keyPath = "/wxmini_pay_ca/apiclient_key.pem";
                    //从classespath获取证书
                    InputStream resourceAsStream = getClass().getResourceAsStream(keyPath);
                    File dir = new File("/wxmini_pay_ca");
                    if (!dir.exists()) {
                        dir.mkdirs();
                    }
                    //复制到jar同级目录
                    FileUtils.copyInputStreamToFile(resourceAsStream,new File(keyPath));
                    this.privateKeyPath = keyPath;
                }catch (Exception e){
                    log.info("文件不存在");
                }
            }
            // 初始化商户配置
            this.config = new RSAAutoCertificateConfig.Builder()
                    .merchantId(this.mchid)
                    // 使用 com.wechat.pay.java.core.util 中的函数从本地文件中加载商户私钥，商户私钥会用来生成请求的签名
                    .privateKeyFromPath(this.privateKeyPath)
                    .merchantSerialNumber(this.serialNumber)
                    .apiV3Key(this.payApiV3Key).build();
            log.info("payConfig初始化成功-----------");
        }catch (Exception e){
            log.error("payConfig初始化失败",e);
        }
    }
 

    /**
     * wx退款api
     * @return
     */
    @Bean
    public RefundService createRefund(){
        if (this.config == null){
            createConfig();
        }
        return new RefundService.Builder().config(this.config).build();
    }

    /**
     * 创建订单api
     * @return
     */
    @Bean
    public JsapiService createJsapiService(){
        if (this.config == null){
            createConfig();
        }
        return new JsapiService.Builder().config(this.config).build();
    }

}

Service层

@Autowired
    private JsapiService jsapiService;

@Autowired
    private WxMiniConfiguration wxMiniConfiguration;

 /**
     * 支付
     * @param wmOrder 订单编号  //支付金额  单位是元  方法内转换为分
     *
     */
    private  WmAffirmDto pay(WmOrder wmOrder){
        Amount amount = new Amount();
        Payer payer = new Payer();
        amount.setTotal(wmOrder.getActualMoney()
                .multiply(new BigDecimal(100)).intValue());// 分为单位
       //需要当前支付用户的openid
        payer.setOpenid(SecurityUtils.getLoginUser().getWxUser().getOpenid());
        PrepayRequest preRequest = new PrepayRequest();
        preRequest.setAmount(amount);
        preRequest.setAppid(wxMiniConfiguration.getAppid());//小程序id  
        preRequest.setMchid(wxMiniConfiguration.getMchid());//商户id
        preRequest.setDescription("xx");//详情
        preRequest.setNotifyUrl(wxMiniConfiguration.getNotifyUrl()); //回调
        preRequest.setOutTradeNo(wmOrder.getOrderCode()); 
        preRequest.setPayer(payer);

        //创建订单
    

        //新增支付信息
        //...
        return paySignRSA(wmOrder.getOrderCode(),prepay.getPrepayId());//记录付费
    }

 /***
     * 支付签名计算
     * @param code  订单编号
     * @param prepayId  支付id
     * @return  返回 WmAffirmDto
     */
    private WmAffirmDto paySignRSA(String code,String prepayId){
        //支付签名计算
        String timeStamp = String.valueOf(System.currentTimeMillis());
        String paySign = String.format("%s\n%s\n%s\nprepay_id=%s\n",
                wxMiniConfiguration.getAppid(),timeStamp,code,prepayId);
        SignatureResult sign = 
        wxMiniConfiguration.getConfig().createSigner().sign(paySign);//计算
        String paySignRSA = sign.getSign();
        //自己写的实体  自己写个
        WmAffirmDto wmAffirmDto = new WmAffirmDto();
        wmAffirmDto.setNonceStr(code);
        wmAffirmDto.setSignType("RSA");
        wmAffirmDto.setTimeStamp(timeStamp);
        wmAffirmDto.setPrepay_id(prepayId);
        wmAffirmDto.setPaySign(paySignRSA);
        return wmAffirmDto;
    }



/**
     * 支付回调
     *
     * @param notification
     * @return
     */ 
    @Transactional
    public ResponseEntity.BodyBuilder parseOrderNotify(HttpServletRequest request, Notification notification) {
        try {
            //获取body
            ByteArrayOutputStream result = new ByteArrayOutputStream();
            ServletInputStream inputStream = request.getInputStream();
            try {
                byte[] buffer = new byte[1024];
                for (int length; (length = inputStream.read(buffer)) != -1; ) {
                    result.write(buffer, 0, length);
                }
            } catch (IOException e) {
                log.error("读取数据流异常:{}", e.toString());
            }
            log.info("body:" + result.toString("UTF-8"));
            String body = result.toString("UTF-8");;
            // 签名的验证及解密
            // 构建request，传入必要参数
            RequestParam requestParam = new RequestParam
                    .Builder()
                    .serialNumber(request.getHeader("Wechatpay-Serial"))
                    .nonce(request.getHeader("Wechatpay-Nonce"))
                    .signature(request.getHeader("Wechatpay-Signature"))
                    .signType(request.getHeader("Wechatpay-Signature-Type"))
                    .timestamp(request.getHeader("Wechatpay-Timestamp"))
                    .body(body)
                    .build();
            // 从notification中获取解密报文
            NotificationParser parser = new NotificationParser(wxMiniConfiguration.getConfig());
            Transaction transaction= parser.parse(requestParam, Transaction.class);
            String outTradeNo = transaction.getOutTradeNo();
            //订单信息处理
          
            //支付成功改为已支付
             
            // 处理成功，返回 200 OK 状态码
            return ResponseEntity.status(HttpStatus.SUCCESS);
        }catch (Exception e){
            log.error("微信支付回调失败",e);
            return ResponseEntity.status(HttpStatus.ERROR);
        }
    }