Http Post Request Parameters is coming as null

When external system calls my vaadin application URL implemented using @springui with post parameter like opentoken info, am not able to get that post parameter in UI init method…i read some topics in forum…looks like its a limitation in Vaadin…am using vaadin 8.0 now…is there any fix in vaadin 8 or workaround? cos of this i could not acheive the siteminder authorization. Please help