Java Web Nine large built-in objects (i)

A total of nine built-in objects are defined in the JSP, namely:

*request HttpServletRequest;

*response HttpServletResponse;

*session HttpSession;

Page this (the JSP page);

*application ServletContext;

Config servletconfig;

Exception display abnormal, special case use;

The out JspWriter can operate on the data buffer;

PageContext use common Java class to access Web resources, commonly used as custom tags;

Nine built-in objects can also be divided into:

Output input object: Request object Response object out object;

Communication Control object: PageContext Object Session object Application object;

Servlet object: Page Object config object;

Error Handling object: Exception object;

Four scopes:

Application; Global scope, server boot to stop

Session; Session scope, user first Access creates a scope, life cycle: Session timeout or server forced shutdown;

PageContext (Page); Within a JSP page

Request; Request scope, one request is dead.

Nine large built-in object scope scopes:

Request object scope: requests;

Response Response Object scope: page;

PageContext page Context Objects scope: page;

Session Conversation Object scope: session;

Application Application Object scope: application;

Out output object scope: Page;

Config Configuration object scope: Page;

Page object scope: pages;

Exception Exception Object scope: Page; Can be used only on pages that contain iserrorpage= "true"

Java Web Nine large built-in objects (i)