1.Servlet is the norm between Java applications and Web servers, or interface
2.Servlet is multithreaded singleton
3.URI: URL after removing the remaining portion of the host request protocol and
4. The request forwarding and redirection
request forwarding: forward () method, the jump in the server, without changing the address bar
redirection: sendRedirect () method, that the server jumps, will change the address bar
The access path
absolute path = path with reference to a relative path +
6. Stack memory thread safety problem does not exist, and methods of heap memory area of memory exists thread-safety issues
(This is written before, save for the draft, it is now made public, would add more detail later)