项目中需要接入支付宝退款功能，根据支付宝API Demo，代码如下：
public class AlipayRefund {private static final Logger logger = LoggerFactory.getLogger(AlipayRefund.class);/*** 支付宝退款方法* @param orderId 订单id* @param tradeNo 支付宝交易号* @param totalAmount 退款金额，该金额不能大于订单金额,单位为元，支持两位小数* @param refundId 标识一次退款请求，同一笔交易多次退款需要保证唯一，如需部分退款，则此参数必传* @return*/public static Result alipayCreateOrderRefund(String orderId,String tradeNo,String totalAmount,String refundId) {Result res = new Result();if(Validata.isNullOrEmpty(orderId) || Validata.isNullOrEmpty(tradeNo) || Validata.isNullOrEmpty(totalAmount)){res.setCode(Result.CODE_PARA_ERROR);res.setMsg("方法必传参数有误");return res;}//AlipayClient alipayClient = new com.alipay.api.DefaultAlipayClient("/gateway.do","app_id","your private_key","json","GBK","alipay_public_key","RSA2");AlipayClient alipayClient = new com.alipay.api.DefaultAlipayClient(AlipayConstant.GET_WAY, AlipayConstant.APP_ID, AlipayConstant.ALIPAY_PRIVATE_KEY,AlipayConstant.FORMAT, AlipayConstant.CHARSET, AlipayConstant.ALIPAY_PUBLIC_KEY, AlipayConstant.SIGN_TYPE);AlipayTradeRefundRequest request = new AlipayTradeRefundRequest();AlipayTradeRefundModel model= new AlipayTradeRefundModel();model.setOutTradeNo(orderId);//订单支付时传入的商户订单号model.setTradeNo(tradeNo);//支付宝交易号model.setRefundAmount(totalAmount);//refund_amount 需要退款的金额，该金额不能大于订单金额,单位为元if(!Validata.isNullOrEmpty(refundId)){model.setOutRequestNo(refundId);}request.setBizModel(model);//请求参数AlipayTradeRefundResponse response = null;try {response = alipayClient.execute(request);if(response.isSuccess()){res.setCode(Result.CODE_OK);logger.info("支付宝：支付订单支付结果查询：订单out_trade_no----"+orderId+"---订单退款成功！");} else {res.setCode(Result.CODE_ERROR);logger.info("支付宝：支付订单支付结果查询：订单out_trade_no----"+orderId+"---订单退款失败！");}res.setMsg(response.getSubMsg());}catch ( AlipayApiException e){res.setCode(Result.CODE_ERROR);res.setMsg("调用支付宝退款接口失败");logger.error("支付宝订单退款失败", e);}return res;}}
