e.g., malformed request syntax, invalid request message framing, or deceptive request routing

HTTP Status 400 – Bad Request
Required String parameter ‘productName’ is not present
The server cannot or will not process the request due to something that is perceived to be a client error (e.g., malformed request syntax, invalid request message framing, or deceptive request routing).

可能：
1）Mapper的返回类型有误，导致controller 的Service返回类型出现错误
2）Controller @RequestParam(“productName”)写错
3） @RequestParam有个require参数，默认为true，表示必须传递传递该参数，如果不是必须的设置为require=false