pageContext

1. scope in jsp/servlet: scope of a attribute is limited in a scope (Phạm vi của một attribute nằm giới hạn trong phạm vi nào đó)

scope level 1 (lowest) : jsp page (only)
scope level 2: request (client- server)
scope level 3: session ( multi request)
scope level 4 (highest) : application (request, page, (multi) through system)

 jsp page < request < session < application (context)
2. method
- setAttribute, getAttribute in this  servlet
- findAttribute by scope (find from low to high, if finded it will stop)