Request Object In JSP
This section illustrates more about the JSP implicit
object called Request object. This object retrieves values whatever
client passes to the server by an HTTP request. Let if you submit the html form
with some data to be send to the server, is received by the HTTP request
object of the JSP. To access the HTML form data we use the request object
and it's several methods like getParameter().
All the things like headers, cookies or parameters are
sent from the client browser to the server during an HTTP request object which
most common use of the request object is to obtain parameter or query string
values. you can illustrates more about the request object for parsing
form data by using the following program when you will direct copy and paste
this in your JSP application.
Methods of the request object is explained one
by one as follows:
request.getParameter(String name):
This is the method, used
for getting the value of the HTML form attribute. This method returns the string
type value i.e. the value of the specified field of an HTML form. This method
takes a string type parameter which is the name of the attribute of the html
which value has to be retrieved through the request object.
request.getParameterNames():
This is the method
of the request object used for getting the enumeration of the attributes
of the html form. These values are later retrieved through the java programming
language by enumerating the retrieved enumerated data by the method of the
request object.
request.getParameterValues(String name):
This is
the method of the request object used for getting the string array containing all of
the values which are contained by the request parameter. This method takes a
String type parameter which is the name of the field of the html form. This
method is used where the array of controls of the HTML lies. All the control of
the HTML form contains same name and then makes a control array.
request.getCookies():
This is the method of the
request object used for getting all the cookies existed in the HTTP request
object.
request.getQueryString():
This is the method of
the request object used for getting the query string which is the values with
the attribute of the html from where the jsp page is referenced.
request.getRequestURI():
This is the method of
the request object used for getting the URI of the current page.
request.getHeaderNames():
This method returns
the enumerator of all HTTP header names means this method retrieves name of all
the headers in enumeration form that is enumerated and get all the name
one by one by using the Enumeration.nextElement() up to the
last element of the enumeration.
request.getHeader(String hdr):
This is the method return the value of the HTTP header like query string or
the URL. This method takes a string parameter which is the header name retrieved
by the method getHeaderNames() of the request object that gives all the
HTTP header names in the enumeration form which has to be converted into string
form later for getting the value of the value of the HTTP header from if one by
one.
request.getAttribute(String):
This method is used for getting the value of the attribute which is set
through the setAttribute(String attributeName) method of the request
object. This method takes a string type parameter written in double quotes
("") i.e. the attribute name that is specified in the page where the
value of the attribute is set with the attribute name is to be retrieved either
in the current page or any other page by passing the value the attribute name
through the request object by using dispatcher method.
request.getAttributeNames():
Above method is used for retrieving all the attributes name in the current
session of the page. This method returns the enumerated data which is to be
retrieved later by enumerating.
request.setAttribute(String, object):
Above method sets the value of the attribute for the request which is
retrieved later either in the current JSP page or the another JSP page by
passing the request object through the dispatcher method. The set value of the
attribute is retrieved by the getAttribute(String) method of the request
object.
request.removeAttribute(String):
This method removes the attribute. This method takes a string type parameter
i.e. the attribute name that has to be removed. After applying this method you
can't access the attribute. If you specify the method for getting the value of
the attribute what has removed, you will get the null value.
This section provides two file for the best explanation
about the request object in JSP. These files are as follows:
Above mentioned html file is used for the constructing
a form with a file username and another field is the password. When you submit
the form you will redirect to the above mentioned JSP file that will show the
entered username and the password in a table.
Here is the code the html file:
<html>
<head><title>Request Object In JSP.</title></head>
<body>
<form action="RequestObjectInJSP.jsp" method="post">
<table border="0" cellspacing="0" cellpadding="0">
<tr>
<td>User Name: </td>
<td><input type="text" size="20" name="txtUserName" />
</tr>
<tr>
<td>Password: </td>
<td><input type="password" size="20" name="txtPassword" />
</tr>
<tr>
<td> </td>
<td><input type="submit" value="Submit" name="B1" /></td>
</tr>
</table>
</form>
</body>
</html>
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Output for the html file:
Here is the code of the JSP file:
<%@page import="java.util.*" %>
<%
String username, password;
if(request.getParameter("txtUserName") == null)
username = "";
else
username = request.getParameter("txtUserName");
if(request.getParameter("txtPassword") == null)
password = "";
else
password = request.getParameter("txtPassword");
%>
<table align="center" bgcolor="ffff00" border="1" cellspacing=
"0" cellpadding="0">
<tr>
<td align><b>Your User Name: </b></td>
<td><%=username %><br/></td>
</tr>
<tr>
<td><b>Your Password: </b></td>
<td><%=password %></td>
</tr>
</table>
|
Output for the above JSP code:
Download html
file.
Download jsp file.
|
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