What are the Servlet equivalents to all the CGI environment variables?

Alex Chaffee

The following CGI environment variables, and their descriptions, were taken from the CGI specification, at http://hoohoo.ncsa.uiuc.edu/cgi/env.html. Please see http://java.sun.com/products/servlet/2.2/javadoc/index.html for a full description of the Servlet Request object. It allows direct access to many things that are not available as CGI environment variables, including Parameters, Cookies, HTTP Headers, and Sessions.

CGI VariableServlet Request Method
The name and version of the information server software answering the request (and running the gateway). Format: name/version
SERVER_NAME getServerName()
The server's hostname, DNS alias, or IP address as it would appear in self-referencing URLs.
The revision of the CGI specification to which this server complies. Format: CGI/revision
The name and revision of the information protcol this request came in with. Format: protocol/revision
SERVER_PORT getServerPort()
The port number to which the request was sent.
The method with which the request was made. For HTTP, this is "GET", "HEAD", "POST", etc.
PATH_INFO getPathInfo()
The extra path information, as given by the client. In other words, scripts can be accessed by their virtual pathname, followed by extra information at the end of this path. The extra information is sent as PATH_INFO. This information should be decoded by the server if it comes from a URL before it is passed to the CGI script.
PATH_TRANSLATED getPathTranslated()
The server provides a translated version of PATH_INFO, which takes the path and does any virtual-to-physical mapping to it.
SCRIPT_NAME getServletPath()
A virtual path to the script being executed, used for self-referencing URLs.
QUERY_STRING getQueryString()
also see getParameter() , getParameterValues(), etc..
The information which follows the ? in the URL which referenced this script. This is the query information. It should not be decoded in any fashion. This variable should always be set when there is query information, regardless of command line decoding.
REMOTE_HOST getRemoteHost()
The hostname making the request. If the server does not have this information, it should set REMOTE_ADDR and leave this unset.
REMOTE_ADDR getRemoteAddr()
The IP address of the remote host making the request.
AUTH_TYPE getAuthType()
If the server supports user authentication, and the script is protects, this is the protocol-specific authentication method used to validate the user.
REMOTE_USER getRemoteUser()
If the server supports user authentication, and the script is protected, this is the username they have authenticated as.
REMOTE_IDENT ? - but if a server supports RFC 931, it should probably pass this in getRemoteUser()
If the HTTP server supports RFC 931 identification, then this variable will be set to the remote user name retrieved from the server. Usage of this variable should be limited to logging only.
CONTENT_TYPE getContentType()
For queries which have attached information, such as HTTP POST and PUT, this is the content type of the data.
CONTENT_LENGTH getContentLength()
The length of the said content as given by the client.
The HTTP header lines received from the client, if any, are placed into the environment with the prefix HTTP_ followed by the header name. An example of this is the HTTP_ACCEPT variable which was defined in CGI/1.0. Another example is the header User-Agent. The HTTP Headers are available through getHeader(String), getHeaders(String) and getHeaderNames()
HTTP_ACCEPT getHeader("Accept")
The MIME types which the client will accept, as given by HTTP headers. Other protocols may need to get this information from elsewhere. Each item in this list should be separated by commas as per the HTTP spec. Format: type/subtype, type/subtype
HTTP_USER_AGENT getHeader("User-Agent")
The browser the client is using to send the request. General format: software/version library/version.