Let’s Move on:

JSP ObjectsAn overview

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JSP Objects

Built-in JSP Objects and Their Implementation Classes:

JSP Object Implementation Class

Request HttpServletRequest

response HttpServletResponse

out JspWriter

session HttpSession

application ServletContext

pageContext PageContext

config ServletConfig

page Object

exception Throwable

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Cont ‘d … JSP Objects

These objects are implicitly created at the beginning of a page when your JSP is invoked, and they directly reference objects in the underlying servlet.

They are always available to scriptlets and expressions.

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a brief descriptionThe requestObject

The request object represents the current request from the browser and is a subclass of the

ServletRequest class. For most current implementations of JSP, the request object is an

instance of HttpServletRequest.

The responseObject

Like the request object, the response object is usually a subclass of the HTTP-specific version

of ServletResponse. In other words, it is usually an instance of HttpServletResponse.

The out Object

The out object is responsible for writing responses back to the browser and is an instance of the

JspWriter class.

The sessionObject

The session object is an instance of HttpSession. Because there is an obvious dependence on

HTTP, this object is available only if your JSPs use HTTP.

The application ObjectThe application object is an instance of the ServletContext object. The names "application" and "ServletContext" don't seem very similar, but if you recall what the ServletContext class does, you'll see that it manages data at the application level.

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Cont ‘d… a brief description

The pageContext ObjectThe pageContext object is an instance of the PageContext class. Many of the

items available through built-in variables are also available through the pageContext object.

The config ObjectThe config object gives you access to configuration information for your JSP and

is an instance of the ServletConfig class.

The page ObjectThe page object is rather peculiar because it is a reference to the current JSP. In

other words, it's like an alias for the this keyword in Java.

The exception ObjectWhen you create an error page to deal with exceptions that occur during normal

JSP processing, you might need access to the exception that caused the error page to be invoked. You can access that exception through the exception object.

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Request Object in JSP is used to get the values that the client passes to the

web server during an HTTP request. The request object is used to take the value

from the client’s web browser and pass it to the server. This is performed using an

HTTP request such as: headers, cookies or arguments.

The class or the interface name of the object request is

http.httpservletrequest.

The object request is written: Javax.servlet.http.httpservletrequest.

Request Object

JSP Request Object

There are numerous methods available for request Object. Some of them are:

getCookies()

getHeader(String name)

getHeaderNames()

getAttribute(String name)

getAttributeNames()

getMethod()

getParameter(String name)

getParameterNames()

getParameterValues(String name)

getQueryString()

getRequestURI()

getServletPath()

setAttribute(String,Object)

removeAttribute(String)

Request Object

Methods of request Object:

The response object denotes the HTTP Response data. The result or the information of

a request is denoted with this object. The response object handles the output of the client.

This contrasts with the request object. The class or the interface name of the response object

is http.HttpServletResponse.

The response object is written as : Javax.servlet.http.httpservletresponse.

The response object is generally used by cookies. The response object is also used

with HTTP Headers.

Response Object

JSP Response Object

There are numerous methods

available for response object. Some of them are:

setContentType()

addCookie(Cookie cookie)

addHeader(String name, String value)

containsHeader(String name)

setHeader(String name, String value)

sendRedirect(String)

sendError(int status_code)

Methods of response Object:

Response Object

JSP Session Object

Session Object denotes the data associated with a specific session of user. The

class or the interface name of the object session is http.HttpSession.

The object session is written as: Javax.servlet.http.httpsession.

The previous two objects, request and response, are used to pass information

from web browser to server and from server to web browser respectively.The Session

object provides the connection or association between the client and the server. The

main use of Session Objects is to maintain states when there are multiple page

requests.

The main feature of session object is to navigate between multiple pages in a

application where variables are stored for the entire user session. The session objects

do not lose the variables and the value remains for the user’ session. The concept of

maintenance of sessions can be performed by cookies or URL rewriting. A detailed

approach of session handling will be discusses in coming sections.

Session Object

Methods of session Object: There are numerous methods available for session object. Some of them are:

getAttribute(String name)

getAttributeNames

isNew()

getCreationTime

getId

invalidate()

getLastAccessedTime

getMaxInactiveInterval

removeAttribute(String name)

setAttribute(String, object)

Session Object

JSP out object denotes the Output stream in the context of page. The class or the interface name of the object out is jsp.JspWriter.

The out object is written as: Javax.servlet.jsp.JspWriter

The object that write to the JSP's output stream is defined by the out object.

Methods of out Object: There are numerous methods available for out Object,some of them are :

clear

clearBuffer

flush

isAutoFlush

getBufferSize

getRemaining

newLine

print

println

Out ObjectJSP out object