JSP Tutorial - JSP Client Request

When a browser requests a web page, it sends information to the web server in the HTTP header.

We can access the information sent to the server with javax.servlet.http.HttpServletRequest object.

The request object provides methods to get HTTP header information including form data, cookies, HTTP methods etc.

The following listed methods can be used to read HTTP header in JSP page.

Method	Description
Cookie[] getCookies()	Returns an array containing all of the Cookie objects the client sent.
Enumeration getAttributeNames()	Returns an Enumeration containing the names of the attributes for this request.
Enumeration getHeaderNames()	Returns an enumeration of all the header names.
Enumeration getParameterNames()	Returns an Enumeration of String objects containing the names of the parameters
HttpSession getSession()	Returns the current session. If the request does not have a session, creates a new one and return.
HttpSession getSession(boolean create)	Returns the current HttpSession or, if there is no current session and create is true, returns a new session.
Locale getLocale()	Returns the preferred Locale for the client, based on the Accept-Language header
Object getAttribute(String name)	Returns the value of the named attribute, or null if no attribute for the given name.
ServletInputStream getInputStream()	Retrieves the body of the request as binary data using a ServletInputStream.
String getAuthType()	Returns the name of the authentication scheme used to protect the servlet, for example, "BASIC" or "SSL," or null.
String getCharacterEncoding()	Returns the name of the character encoding.
String getContentType()	Returns the MIME type, or null if the type is not known.
String getContextPath()	Returns the portion of the request URI that indicates the context of the request.
String getHeader(String name)	Returns the value of the specified request header as a String.
String getMethod()	Returns the name of the HTTP method, for example, GET, POST, or PUT.
String getParameter(String name)	Returns the value of a request parameter as a String, or null if the parameter does not exist.
String getPathInfo()	Returns path information associated with the URL the client sent.
String getProtocol()	Returns the name and version of the protocol for the request.
String getQueryString()	Returns the query string contained in the request URL after the path.
String getRemoteAddr()	Returns IP address of the client.
String getRemoteHost()	Returns the fully qualified name of the client.
String getRemoteUser()	Returns the login of the user, or null if the user has not been authenticated.
String getRequestURI()	Returns request's URL from the protocol name up to the query string.
String getRequestedSessionId()	Returns the session ID
String getServletPath()	Returns request's URL that calls the JSP.
String[] getParameterValues(String name)	Returns String arrays containing all of the values the given request parameter has
boolean isSecure()	Returns a boolean indicating if the request is from a secure channel, such as HTTPS.
int getContentLength()	Returns the length, in bytes, of the request, or -1 if the length is not known.
int getIntHeader(String name)	Returns the value of the specified request header as an int.
int getServerPort()	Returns the port number on which this request was received.

Example

The following code shows how to use getHeaderNames() method of HttpServletRequest to read the HTTP header infromation.

<%@ page import="java.io.*,java.util.*" %>
<html>
<body>
<table width="100%" border="1" align="center">
<tr bgcolor="#949494">
<th>Header Name</th><th>Header Value(s)</th>
</tr>
<%
   Enumeration headerNames = request.getHeaderNames();
   while(headerNames.hasMoreElements()) {
      String paramName = (String)headerNames.nextElement();
      out.print("<tr><td>" + paramName + "</td>\n");
      String paramValue = request.getHeader(paramName);
      out.println("<td> " + paramValue + "</td></tr>\n");
   }
%>
</table>
</body>
</html>