JSP Implicit Objects

1
JSP Implicit Objects

• CS 422
• Dick Steflik

2
Implicit Objects

• Objects created by the servlet container
• application
• session
• request
• response
• exception
• out
• Config
• pageContext
• page

3
Application Object

• Used to share data between all of the pages that
  make up an application
• All users share the Application Object
• Can be accessed from any JSP in the application
  via the ServletContext
• javax.servlet.http.ServletContext

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Application Object Methods

• getAttribute(String name)
• getAttributeNames
• setAttribute(String objName, Object object)
• removeAttribute(String objName)
• getMajorVersion()
• getMinorVersion()
• getServerInfo()
• getInitParameter(String name)
• getInitParameterNames
• getResourceAsStream(Path)
• log(Message)

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Sessions

• A session is a concept that represents a series
  of HTTP requests and responses between a specific
  browser and a specific server.
• Sessions are managed by the server
• Created by the server when the first request is
  received from a browser on a new host the server
  starts the session and assigns it an ID.
• The ID is sent to the browser as a cookie and
  remembered by the server

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Sessions (more)

• The server creates a Session object that contains
  the attributes
• Creation Time
• ID
• Last Time Accessed
• Maximum Inactive Time allowed

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HTTPSession Interface

• getAttribute() returns the object associated
  with the specified key string
• getAttributeNames() returns an enumeration of
  the key strings in the session
• getCreationTime() returns the time the session
  was created millsecs past midnight since Jan 1,
  1970 GMT
• getID() returns the session ID as a string
• getLastAccessedTime() returns thelast time the
  client sent a request for this session
• getMaxInactiveInterval() returns the maximun
  amount of time that the servlet container between
  client requests before timing out the session
• setAttribute() associates an object with a key
  string in the session
• removeAttribute() remove an attribute from the
  session
• setMaxInactiveInterval() set the time in
  seconds allowed between client requests
• isNew() true if a new session, false otherwise

8
request Object

• Javax.servlet. http.httpservletrequest.
• The object request is of type Javax.servlet.http.h
  ttpservletrequest.
• This denotes the data included with the HTTP
  Request.
• The client makes a request that is then passed to
  the server.
• The requested object is used to take the value
  from clients web browser and pass it to the
  server.
• This is performed using HTTP request like
  headers, cookies and arguments.

9
response Object

• Javax.servlet.http.HttpServletResponse
• The HTTP Response data.
• The result or the information that fulfills an
  Http request
• The object response is of type javax.servlet.http.
  gthttpservletresponse. Generally, the object
  response is used with cookies. The response
  object is used to build the HTTP response header

10
pageContext Object

• Javax.servlet.jsp.pagecontext
• Used to access page attributes and also to access
  all the namespaces associated with a JSP page.

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Out Object

• The Output stream in the context of page.
• The class or the interface name of the Out object
  is jsp.JspWriter.
• The Out object is written Javax.servlet.jsp.JspWr
  iter

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config Object

• This is used to get information regarding the
  Servlet configuration
• The class or the interface name of the Config
  object is ServletConfig.
• The object Config is written Javax.servlet.http.Se
  rvletConfig

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page Object

• The Page object denotes the JSP page
• Used for calling any instance of a Page's
  servlet.
• The class or the interface name of the Page
  object is jsp.HttpJspPage.
• The Page object is written Java.lang.Object

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Passing Values from Page to Page

• Put values in the session object
• Put the values in the application object
• Put values at the end of the URL