AlipayClient alipayClient = new DefaultAlipayClient("https://openapi.alipay.com/gateway.do", "app_id", "your private_key", "json", "GBK", "alipay_public_key", "RSA2");
ZhimaCreditPeZmgoSettleRefundRequest request = new ZhimaCreditPeZmgoSettleRefundRequest();
request.setBizContent("{" +
    "\"agreement_id\":\"ZMGO_AGR2021010510020604080000006001\"," +
    "\"partner_id\":\"2088302424614288\"," +
    "\"alipay_user_id\":\"2088302841345600\"," +
    "\"refund_amount\":3.00," +
    "\"out_request_no\":\"99202005050100930053707258\"," +
    "\"memo\":\"退款\"," +
    "\"withhold_plan_no\":\"ZMGO_WHD2021010510020603410000006001\"," +
    "\"refund_type\":\"MEMBER_FEE_REFUND\"" +
    "  }");
ZhimaCreditPeZmgoSettleRefundResponse response = alipayClient.execute(request);
if (response.isSuccess()) {
    System.out.println("调用成功");
} else {
    System.out.println("调用失败");
}

{
    "zhima_credit_pe_zmgo_settle_refund_response": {
        "code": "10000",
        "msg": "Success",
        "out_request_no": "99202005050100930053707258",
        "withhold_plan_no": "ZMGO_WHD2021010510020603410000006001",
        "refund_amount": "3.00",
        "fail_reason": "退款金额超限",
        "retry": true
    },
    "sign": "ERITJKEIJKJHKKKKKKKHJEREEEEEEEEEEE"
}

{
    "zhima_credit_pe_zmgo_settle_refund_response": {
        "code": "20000",
        "msg": "Service Currently Unavailable",
        "sub_code": "isp.unknow-error",
        "sub_msg": "系统繁忙"
    },
    "sign": "ERITJKEIJKJHKKKKKKKHJEREEEEEEEEEEE"
}