How to block request if Context-Type contains “addHeader”

问题

I want to block a request if contains in header "addHeader". How can I do this?. I already search on Google and find doFilter method but I don't understand how I using this. There is no explanatory examples for me. In jsp file I have already write this code block;

String example  = request.getHeader("Content-Type") + " This is from req. header";
System.out.println(example);
if(example.contains("addHeader")){

    System.out.println("Contains AddHeader!!");
    Block Req.

}

Thanks for helping :)

来源：https://stackoverflow.com/questions/57552843/how-to-block-request-if-context-type-contains-addheader