Introduction to 'request' implicit object
When the webserver receives an http request, it bundles everything (headers, parameters, cookies) that it receives from the http client in a request object and this object is implicitly available to all jsp pages.
request object is an instance of javax.servlet.http.HttpServletRequest.
The example below shows how to get the http parameter "username" from the request object.
request object is an instance of javax.servlet.http.HttpServletRequest.
The example below shows how to get the http parameter "username" from the request object.
<html>
<body>
Welcome <%= request.getParameter("username") %>
</body>
</html>
The above code will produce the webpage shown below. Notice the parameter "username" in the url.
The other commonly used methods of the request object are :
| Method | Description |
|---|---|
| String getParameter(String) | Gets the parameter sent by http client |
| String[] getParameterValues(String) | Same as above, if parameter has multiple values as in select dropdown list, gets them as an array |
| Enumeration |
Gets names of all parameters |
| Map getParameterMap() | Gets map of parameter names and values |
| String getHeader(String) | Get header value |
| Enumeration |
Gets all the headers |
| Enumeration |
Gets all header names |
| HttpSession getSession() | Gets |
| HttpSession getSession(boolean) | Gets the session of the http client |
| String getContentType() | Gets the content type sent by http client/browser in header |
| int getContentLength() | Gets the length of request body sent by http client in header |
| String getCharacterEncoding() | Gets the request's encoding sent by http client in header |
| String getContextPath() | Gets the webapp's name that the http url points to |
| String getMethod() | Gets the http method of the request made by client |
| String getServletPath() | Returns the part of this request's URL that calls the servlet |
| String getQueryString() | Gets the parameters contained in the request URL after the path |
| String getRequestURL() | Gets the complete url of http request |
| String getRemoteAddr() | Gets the ip of http client |
| String getRemoteHost() | Gets the hostname of http client |
| int getRemotePort() | Gets the tcp port of the http client machine used in the request |
| String getLocalAddr() | Gets local(webserver's) ip address |
| String getServerName() | Gets the local(webserver machine's) hostname |
| int getLocalPort() | Gets the tcp port actually involved in http request, different from getServerPort() |
| int getServerPort() | Gets the port on which webserver listens for incoming http request |
| Object getAttribute(String) | Gets the attribute that jsp developer stores in request object |
| setAttribute(String, Object) | Sets an object as an attribute in request object |
| removeAttribute(String) | Removes attribute from request object. |
| Enumeration |
Gets names of all attributes stored in the request scope |
| Cookie[] getCookies() | Gets all cookies sent by http client |