调用JSON API时已设置Content-Type为application/json仍报415错误，如何修复？

重现环境 #

执行的Curl命令：

curl -i -k -X POST -H "Content-Type: application/json" -d "{\"niceSessionKey\": \"S202320220722145915340287\",\"fiCode\": \"B100000022\",\"taskCode\": \"KYC_VC2_RSLT\",\"appNumber\": \"APPL000000000000999\",\"customerNumber\": \"12345678\",\"mobilePhoneNumber\": \"0966688526\"}" https://100.113.125.128:8080/api/KYT_VC7_RSLT

服务器返回错误：

"status":"UNSUPPORTED_MEDIA_TYPE","message":"Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported","errors":["application/x-www-form-urlencoded;charset=UTF-8 media type is not supported. Supported media types are application/octet-stream, text/plain, application/xml, text/xml, application/x-www-form-urlencoded, application/*+xml, multipart/form-data, application/json, application/*+json, */*"]}

解决方法 #

1. 修正JSON数据的包裹方式，避免转义错误 #

你的命令中用双引号包裹JSON并转义内部双引号，在部分shell环境下可能导致curl无法正确识别JSON格式，转而默认使用application/x-www-form-urlencoded编码。改为用单引号包裹JSON内容，无需转义内部双引号：

curl -i -k -X POST -H "Content-Type: application/json" -d '{"niceSessionKey": "S202320220722145915340287","fiCode": "B100000022","taskCode": "KYC_VC2_RSLT","appNumber": "APPL000000000000999","customerNumber": "12345678","mobilePhoneNumber": "0966688526"}' https://100.113.125.128:8080/api/KYT_VC7_RSLT

2. 验证请求头是否真实发送 #

添加-v参数查看curl实际发送的请求头，确认Content-Type: application/json是否被正确传递：

curl -v -i -k -X POST -H "Content-Type: application/json" -d '{"niceSessionKey": "S202320220722145915340287","fiCode": "B100000022","taskCode": "KYC_VC2_RSLT","appNumber": "APPL000000000000999","customerNumber": "12345678","mobilePhoneNumber": "0966688526"}' https://100.113.125.128:8080/api/KYT_VC7_RSLT

查看输出中类似以下的内容，确认存在Content-Type: application/json：

> POST /api/KYT_VC7_RSLT HTTP/1.1
> Host: 100.113.125.128:8080
> User-Agent: curl/7.68.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 248

3. 检查中间件是否篡改请求头 #

如果你的请求经过代理、负载均衡或网关，这些中间件可能会修改请求头。需要确认此类服务是否存在自动替换Content-Type的配置。

4. 验证JSON格式合法性 #

确保你的JSON内容格式正确，比如没有遗漏逗号、引号匹配正确。可以用jq工具验证：

echo '{"niceSessionKey": "S202320220722145915340287","fiCode": "B100000022","taskCode": "KYC_VC2_RSLT","appNumber": "APPL000000000000999","customerNumber": "12345678","mobilePhoneNumber": "0966688526"}' | jq .

如果格式正确，jq会格式化输出JSON；如果错误，会提示具体问题。

内容的提问来源于stack exchange，提问作者Khanh Luong Van