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Request Object in JSP is most usable object. This request object take information from the user and send to server, then this request is proceed by server and response back to user. The process starts when we write address of any page in browser and press enter to page. Request object can be used in
Query String
When using query String, data is passed to server in form of URL string. This URL string is visible on browser and anyone can see it. E.g
http://www.domainName.com/concerts.jsp?id=9&type=Exhibition
This is query string after page name. id is key and 9 is value. This query String either self made or can send by form property. This can get with request.getParameter(“Key”) method. This will give us 9.
Query String self made example in JSP
queryString.jsp
<%@ page language="java" import="java.sql.*" %>
<html>
<head>
<title>Query String in JSP</title>
</head>
<body>
<a href="queryString.jsp?id=9&name=joe">This is data inside query string</a>
<%
String queryString=request.getQueryString();
out.print("<br>"+queryString);
%>
</body>
</html>
We can get single id and value instead of using getQueryString method of request.
Query String example with getParameter
queryStringParameter.jsp
<%@ page language="java" import="java.sql.*" %>
<html>
<head>
<title>Query String in JSP</title>
</head>
<body>
<a href="queryString.jsp?id=9&name=joe">This is data inside query string</a>
<%
String queryStringVariable1=request.getParameter("id");
String queryStringVariable2=request.getParameter("name");
out.print("<br>"+queryStringVariable1);
out.print("<br>"+queryStringVariable2);
%>
</body>
</html>
Form
Form is most important part of request object in JSP. It takes value from user and sends it to server for further processing. Suppose we have a registration form, and value in field have to save in database. We need to get these values from browse and get in server side; once we get this value in java, we can save in database through JDBC or any database object. Form in html has two properties get or post method, get method send information to server in query string. Post method doesn’t send data in query string in to server. When data is sent to server it is not visible on browser. Post method as compare to get method is slower. Get method has a limit of string length in some kilobytes.
Form Example in JSP with request object
formGetMethod.jsp
<%@ page language="java" import="java.sql.*" %>
<%
String queryStringVariable1=request.getParameter("name");
String queryStringVariable2=request.getParameter("className");
%>
<html>
<head>
<title>Query String in JSP</title>
</head>
<body>
<%
out.print("<br>Field 1 :"+queryStringVariable1);
out.print("<br>Field 2 :"+queryStringVariable2);
%>
<form method="get" name="form1">
Name <input type="text" name="name"> <br><br>
Class <input type="text" name="className"> <br><br>
<input type="submit" name="submit" value="Submit">
</form>
</body>
</html>
Request object with Check box form in JSP
formGetParameterValues.jsp
<%@ page language="java" import="java.sql.*" %>
<%
String queryStringVariable1=request.getParameter("name");
String[] queryStringVariable2=request.getParameterValues("className");
%>
<html>
<head>
<title>Query String in JSP</title>
</head>
<body>
<%
try{
out.print("<br>Field 1 :"+queryStringVariable1);
for(int i=0;i<=queryStringVariable2.length;i++){
out.print("<br>Check box Field "+i+" :"+queryStringVariable2[i]);
}
}
catch(Exception e)
{
e.printStackTrace();
}
%>
<br>
<br>
<form method="get" name="form1">
Name <input type="text" name="name"> <br><br>
class 1
<input type="checkbox" name="className" value="c1">
class 2 <input type="checkbox" name="className" value="c2"><br><br>
<input type="submit" name="submit" value="Submit">
</form>
</body>
</html>
Request object with radio button form in JSP
formGetRadio.jsp
<%@ page language="java" import="java.sql.*" %>
<%
String inputVariable=request.getParameter("name");
String[] radioVariable=request.getParameterValues("className");
%>
<html>
<head>
<title>Query String in JSP</title>
</head>
<body>
<%
try{
out.print("<br>Field 1 :"+inputVariable);
for(int i=0;i<=radioVariable.length;i++){
out.print("<br>Check box Field "+i+" :"+radioVariable[i]);
}
}
catch(Exception e)
{
e.printStackTrace();
}
%>
<br>
<br>
<form method="get" name="form1">
Name <input type="text" name="name"> <br><br>
class 1
<input type="radio" name="className" value="c1">
class 2 <input type="radio" name="className" value="c2"><br><br>
<input type="submit" name="submit" value="Submit">
</form>
</body>
</html>
Cookies
Cookies use request object to get values through in cookie file. It uses request.getCookies() method to get cookie and return in cookie[] array.
Server variable
Server variable give server information or client information. Suppose we need to get remote client IP address, browser, operating system, Context path, Host name any thing related to server can be get using request object in JSP.
Server variable example in JSP
serverVariable.jsp
<%@ page contentType="text/html; charset=utf-8" language="java" %>
<html>
<head>
<title>Server Variable in JSP</title>
</head>
<body>
Character Encoding : <b><%=request.getCharacterEncoding()%></b><br />
Context Path : <strong><%=request.getContextPath()%></strong><br />
Path Info : <strong><%=request.getPathInfo()%></strong><br />
Protocol with version: <strong><%=request.getProtocol()%></strong><br />
Absolute Path file:<b><%=request.getRealPath("serverVariable.jsp")%></b><br/>
Client Address in form of IP Address:<b><%=request.getRemoteAddr()%></b><br/>
Client Host : <strong><%=request.getRemoteHost()%></strong><br />
URI : <strong><%=request.getRequestURI()%></strong><br />
Scheme in form of protocol : <strong><%=request.getScheme()%></strong><br />
Server Name : <strong><%=request.getServerName()%></strong><br />
Server Port no : <strong><%=request.getServerPort()%></strong><br />
Servlet path current File name : <b><%=request.getServletPath()%></b><br />
</body>
</html>
Properties and method of Request objects
| Method |
Return |
Description |
| equals(Object obj) |
Objects |
Matching objects |
| getAttribute(String str) |
Objects |
Returns the String associated with name in the request scope |
| getAttributeNames() |
Enumeration |
an Enumeration of attribute names |
| getAuthType() |
String |
|
| getCharacterEncoding() |
String |
Returns character encoding for page in request MIME type charset=iso-8859-1 |
| getContentLength() |
int |
get length of content body in request |
| getContentType() |
String |
|
| getContextPath() |
String |
|
| getCookies() |
Cookie[] |
|
| getDateHeader(String str) |
long |
get request header with given name and date value |
| getHeader(String str) |
String |
get request header with given name and value |
| getHeaderNames() |
Enumeration |
|
| getHeaders(String str) |
Enumeration |
|
| getInputStream() |
ServletInputStream |
|
| getIntHeader(String str) |
int |
|
| getLocalAddr(String str) |
String |
|
| getLocale(String str) |
Locale |
|
| getLocales() |
Enumeration |
|
| getLocalName() |
String |
|
| getLocalPort() |
int |
|
| getMethod() |
String |
|
| getParameter(String str) |
String |
|
| getParameterMap() |
Map |
|
| getParameterNames() |
Enumeration |
|
| getParameterValues(String str) |
String |
|
| getPathInfo() |
String |
|
| getPathTranslated() |
String |
|
| getProtocol() |
String |
|
| getQueryString() |
String |
|
| getReader() |
BufferedReader |
|
(D) getRealPath() |
String |
|
| getRemoteAddr() |
String |
|
| getRemoteHost() |
String |
|
| getRemotePort() |
int |
|
| getRemoteUser() |
String |
|
| getRequestDispatcher(String str) |
RequestDispatcher |
|
| getRequestedSessionId() |
String |
|
| getRequestURI() |
String |
|
| getRequestURL() |
StringBuffer |
|
| getScheme() |
String |
|
| getServerName() |
String |
|
| getServerPort() |
int |
|
| getServletPath() |
String |
|
| getSession() |
HttpSession |
|
| getSession(boolean true|false) |
HttpSession |
|
| getUserPrincipal() |
Principal |
|
| hashCode() |
int |
|
| isRequestedSessionIdFromCookie() |
boolean |
|
| isRequestedSessionIdFromURL() |
boolean |
|
| isRequestedSessionIdValid() |
boolean |
|
| isSecure() |
boolean |
|
| isUserInRole() |
boolean |
|
| removeAttribute(String str) |
void |
|
| setAttribute(String str, Object obj) |
void |
|
| setCharacterEncoding(String str) |
void |
Set a character encoding for send to client request body charset=iso-8859-1 |
| toString() |
String |
|
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