DefaultHandlerExceptionResolver : Failed to read HTTP message: org.springframework.http.converter.HttpMessageNotReadableException: Required request body is missing

客户端当发送空的json字符串时，请求RestController时，报错：

DefaultHandlerExceptionResolver : Failed to read HTTP message: org.springframework.http.converter.HttpMessageNotReadableException: Required request body is missing: public java.lang.String com.gomepay.xxx.LocaleApi.getLocaleList(java.lang.String)

解决方法是加上：

contentType:'application/json'