（注：本地postman测试是成功的，但是放到外网服务器就报这个错误）

SDK版本：

 <dependency>

            <groupId>com.github.wxpay</groupId>

            <artifactId>wxpay-sdk</artifactId>

            <version>0.0.3</version>

     </dependency>

错误日志：

java.io.IOException: Server returned HTTP response code: 400 for URL: https://api.mch.weixin.qq.com/secapi/pay/refund

at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)

at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)

at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)

at com.github.wxpay.sdk.WXPay.requestWithCert(WXPay.java:208)

at com.github.wxpay.sdk.WXPay.refund(WXPay.java:485)

at com.github.wxpay.sdk.WXPay.refund(WXPay.java:463)