jsp 是什么 ，jsp 隐式对象

google 搜索 java server page

http://www.oracle.com/technetwork/java/javaee/jsp/index.html

http://docs.oracle.com/javaee/5/tutorial/doc/bnagx.html

5.  JavaServer Pages Technology

6.  JavaServer Pages Documents

7.  JavaServer Pages Standard Tag Library

8.  Custom Tags in JSP Pages

9.  Scripting in JSP Pages

什么是pageContext

http://docs.oracle.com/javaee/5/tutorial/doc/bnahq.html#bnahv

Implicit Objects

The JSP expression language defines a set of implicit objects:

• pageContext: The context for the JSP page. Provides access to various objects including:
  • servletContext: The context for the JSP page’s servlet and any web components contained in the same application. See Accessing the Web Context.
  • session: The session object for the client. See Maintaining Client State.
  • request: The request triggering the execution of the JSP page. See Getting Information from Requests.
  • response: The response returned by the JSP page. See Constructing Responses.
• In addition, several implicit objects are available that allow easy access to the following objects:
  • param: Maps a request parameter name to a single value
  • paramValues: Maps a request parameter name to an array of values
  • header: Maps a request header name to a single value
  • headerValues: Maps a request header name to an array of values
  • cookie: Maps a cookie name to a single cookie
  • initParam: Maps a context initialization parameter name to a single value
• Finally, there are objects that allow access to the various scoped variables described in Using Scope Objects.
• pageScope: Maps page-scoped variable names to their values
• requestScope: Maps request-scoped variable names to their values
• sessionScope: Maps session-scoped variable names to their values
• applicationScope: Maps application-scoped variable names to their values