我在做APP支付集成，统一下单，使用官方文档上的示例字符串（mchid和appid换成我自己的真实id）：

{
	"mchid": "1900006XXX",
	"out_trade_no": "APP1217752501201407033233368018",
	"appid": "wxb4ba3c02aa476XXX",
	"description": "Image形象店-深圳腾大-QQ公仔",
	"notify_url": "https://weixin.qq.com/",
	"amount": {
		"total": 1,
		"currency": "CNY"
	}
}

可以得到正常返回：

HttpResponseProxy{HTTP/1.1 200 OK [Server: nginx, Date: Wed, 12 May 2021 08:18:27 GMT, Content-Type: application/json; charset=utf-8, Content-Length: 52, Connection: keep-alive, Keep-Alive: timeout=8, Cache-Control: no-cache, must-revalidate, X-Content-Type-Options: nosniff, Request-ID: 08D29EEE840610CB0718BDD9EEA30620823928A9F805-0, Content-Language: zh-CN, Wechatpay-Nonce: 526de72d9fcc6ea858936887eee30954, Wechatpay-Signature: pJaKBcFLPy1MoVFllaMn9KPsOQKBJwYwqYqm8YX/Sb25NE8+XOCwh+tRfkg0uw3UQlmtzu0hJetTdIz9GEA/eOjDOxtSwemcIrNMxiRvApgF1alZ2yo9wX3X2ix33c4PaYzncfw10I+q3IHSiHA8aoxJKSBZ4sq7cpS5oeL/oAzvmlw/8yR6qFJ43FKtA/gGfH8QW5rK3By2DbTNPsqidH8YWo0QUXy30aHuGPOCFOM3LB8VijeFxG6Gkg+aio5uEH0dm9WJidvXnzPifgkOX49LRrozWcww8nLARggkxLcY4HlX6agwb2fA8ywTYPM7TOMVfynC0UaQZf9HQHIPkQ==, Wechatpay-Timestamp: 1620807507, Wechatpay-Serial: 580B8B545FAA6434669414607F4E995DAEBFCCD3] org.apache.http.entity.BufferedHttpEntity@2c1b194a}
success,return body = {"prepay_id":"wx121618270424679cc4ef63ed8610c10000"}

但是out_trade_no、description、notify_url、total等字段哪怕改动一个字符，比如把金额total从1改成2，就调用失败（以下是把total改成2的结果，其他参数不变）：

HttpResponseProxy{HTTP/1.1 400 Bad Request [Server: nginx, Date: Wed, 12 May 2021 08:21:41 GMT, Content-Type: application/json; charset=utf-8, Content-Length: 64, Connection: keep-alive, Keep-Alive: timeout=8, Cache-Control: no-cache, must-revalidate, X-Content-Type-Options: nosniff, Request-ID: 0894A0EE840610AA0718AAB3B74C20843028F8E704-268498688, Content-Language: zh-CN, Wechatpay-Nonce: 1a4e3a11d31a18c05b89a4e2cc35b1a9, Wechatpay-Signature: HaL+7FvVPIDoN/oO2bFHUCIIhvkjeHh4PowFJSeOiFjTDUCTQS5jYl8/ZRDcpgKDLbvnTDwtKz9+3kFvHsQ14mOnMR297yHC7CvvpuVP4Qe0G7A9dyy7prYeddbkz1IhB6yqnylm7CSXhqCTogUehvrSzsVkDmmuQX75EZilJKE75Rey2iH+OtAaEPJ8D5Zov+aDrbLlh3e9M1BOk/HCCDis4OkxbOgD3w4pg9pwGl91TChww99IlKWa26SgRsX6DMmaXOUr5I83x1JYkbxL6DFuBhtctyzJ4CBKlhFlVO77VT2c1PAljZrxqtVgfS7mbm75nok1ky9xricnlzTF2Q==, Wechatpay-Timestamp: 1620807701, Wechatpay-Serial: 580B8B545FAA6434669414607F4E995DAEBFCCD3] ResponseEntityProxy{[Content-Type: application/json; charset=utf-8,Content-Length: 64,Chunked: false]}}

请问这是怎么回事呀？