异常如下：
Caused by: java.lang.IllegalStateException: Optional int parameter 'id' is not present but cannot be translated into a null value due to being declared as a primitive type. Consider declaring it as object wrapper for the corresponding primitive type.
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.checkValue(HandlerMethodInvoker.java:750)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveRequestParam(HandlerMethodInvoker.java:518)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:355)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:175)
... 38 common frames omitted
解决方法：
将controller层接收数据的int的类型改为将Integer
