AlipayClient alipayClient = new DefaultAlipayClient("https://openapi.alipay.com/gateway.do","app_id","your private_key","json","GBK","alipay_public_key","RSA2");
AlipayTradeRefundApplyRequest request = new AlipayTradeRefundApplyRequest();
request.setBizContent("{" +
"\"out_trade_no\":\"20150320010101001\"," +
"\"trade_no\":\"2014112611001004680073956707\"," +
"\"refund_amount\":200.12," +
"\"refund_reason\":\"正常退款\"," +
"\"out_request_no\":\"HZ01RF001\"," +
"\"operator_id\":\"OP001\"," +
"\"store_id\":\"NJ_S_001\"," +
"\"terminal_id\":\"NJ_T_001\"" +
"  }");
AlipayTradeRefundApplyResponse response = alipayClient.execute(request);
if(response.isSuccess()){
System.out.println("调用成功");
} else {
System.out.println("调用失败");
}

IAopClient client = new DefaultAopClient("https://openapi.alipay.com/gateway.do", "app_id", "merchant_private_key", "json", "1.0", "RSA2", "alipay_public_key", "GBK", false);
AlipayTradeRefundApplyRequest  request= new AlipayTradeRefundApplyRequest() ;
request.BizContent="{" +
"\"out_trade_no\":\"20150320010101001\"," +
"\"trade_no\":\"2014112611001004680073956707\"," +
"\"refund_amount\":200.12," +
"\"refund_reason\":\"正常退款\"," +
"\"out_request_no\":\"HZ01RF001\"," +
"\"operator_id\":\"OP001\"," +
"\"store_id\":\"NJ_S_001\"," +
"\"terminal_id\":\"NJ_T_001\"" +
"  }";
AlipayTradeRefundApplyResponse response=client.execute(request);
Console.WriteLine(response.Body);

$aop = new AopClient ();
$aop->gatewayUrl = 'https://openapi.alipay.com/gateway.do';
$aop->appId = 'your app_id';
$aop->rsaPrivateKey = '请填写开发者私钥去头去尾去回车，一行字符串';
$aop->alipayrsaPublicKey='请填写支付宝公钥，一行字符串';
$aop->apiVersion = '1.0';
$aop->signType = 'RSA2';
$aop->postCharset='GBK';
$aop->format='json';
$request = new AlipayTradeRefundApplyRequest ();
$request->setBizContent("{" .
"\"out_trade_no\":\"20150320010101001\"," .
"\"trade_no\":\"2014112611001004680073956707\"," .
"\"refund_amount\":200.12," .
"\"refund_reason\":\"正常退款\"," .
"\"out_request_no\":\"HZ01RF001\"," .
"\"operator_id\":\"OP001\"," .
"\"store_id\":\"NJ_S_001\"," .
"\"terminal_id\":\"NJ_T_001\"" .
"  }");
$result = $aop->execute ( $request); 

$responseNode = str_replace(".", "_", $request->getApiMethodName()) . "_response";
$resultCode = $result->$responseNode->code;
if(!empty($resultCode)&&$resultCode == 10000){
echo "成功";
} else {
echo "失败";
}

https://openapi.alipay.com/gateway.do?timestamp=2013-01-01 08:08:08&method=alipay.trade.refund.apply&app_id=4868&sign_type=RSA2&sign=ERITJKEIJKJHKKKKKKKHJEREEEEEEEEEEE&version=1.0&biz_content=
  {
"out_trade_no":"20150320010101001",
"trade_no":"2014112611001004680073956707",
"refund_amount":200.12,
"refund_reason":"正常退款",
"out_request_no":"HZ01RF001",
"operator_id":"OP001",
"store_id":"NJ_S_001",
"terminal_id":"NJ_T_001"
  }

//为确保安全通信，需自行验证响应示例中的sign值是否为蚂蚁金服所提供。

{
	"alipay_trade_refund_apply_response":{
		"msg":"Success",
		"code":"10000"
	},
	"sign":"ERITJKEIJKJHKKKKKKKHJEREEEEEEEEEEE"
}

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