public final class CGIServlet extends HttpServlet
Note: This code compiles and even works for simple CGI cases. Exhaustive testing has not been done. Please consider it beta quality. Feedback is appreciated to the author (see below).
If an instance of this servlet was mapped (using
then the following request:
would result in the execution of the script
with the script's
PATH_INFO set to
Recommendation: House all your CGI scripts under
<webapp>/WEB-INF/cgi. This will ensure that you do not
accidentally expose your cgi scripts' code to the outside world and that
your cgis will be cleanly ensconced underneath the WEB-INF (i.e.,
The default CGI location is mentioned above. You have the flexibility to put CGIs wherever you want, however:
The CGI search path will start at webAppRootDir + File.separator + cgiPathPrefix (or webAppRootDir alone if cgiPathPrefix is null).
cgiPathPrefix is defined by setting this servlet's cgiPathPrefix init parameter
derived from http://cgi-spec.golux.com. A work-in-progress & expired Internet Draft. Note no actual RFC describing the CGI specification exists. Where the behavior of this servlet differs from the specification cited above, it is either documented here, a bug, or an instance where the specification cited differs from Best Community Practice (BCP). Such instances should be well-documented here. Please email the Tomcat group with amendments.
The CGI specification defines the following canonical metavariables:
[excerpt from CGI specification]
AUTH_TYPE CONTENT_LENGTH CONTENT_TYPE GATEWAY_INTERFACE PATH_INFO PATH_TRANSLATED QUERY_STRING REMOTE_ADDR REMOTE_HOST REMOTE_IDENT REMOTE_USER REQUEST_METHOD SCRIPT_NAME SERVER_NAME SERVER_PORT SERVER_PROTOCOL SERVER_SOFTWARE
Metavariables with names beginning with the protocol name (e.g., "HTTP_ACCEPT") are also canonical in their description of request header fields. The number and meaning of these fields may change independently of this specification. (See also section 6.1.5 [of the CGI specification].)[end excerpt]
standard input handling: If your script accepts standard input,
then the client must start sending input within a certain timeout period,
otherwise the servlet will assume no input is coming and carry on running
the script. The script's the standard input will be closed and handling of
any further input from the client is undefined. Most likely it will be
ignored. If this behavior becomes undesirable, then this servlet needs
to be enhanced to handle threading of the spawned process' stdin, stdout,
and stderr (which should not be too hard).
If you find your cgi scripts are timing out receiving input, you can set the init parameter
of your webapps' cgi-handling servlet
Metavariable Values: According to the CGI specification, implementations may choose to represent both null or missing values in an implementation-specific manner, but must define that manner. This implementation chooses to always define all required metavariables, but set the value to "" for all metavariables whose value is either null or undefined. PATH_TRANSLATED is the sole exception to this rule, as per the CGI Specification.
NPH -- Non-parsed-header implementation: This implementation does not support the CGI NPH concept, whereby server ensures that the data supplied to the script are precisely as supplied by the client and unaltered by the server.
The function of a servlet container (including Tomcat) is specifically designed to parse and possible alter CGI-specific variables, and as such makes NPH functionality difficult to support.
The CGI specification states that compliant servers MAY support NPH output. It does not state servers MUST support NPH output to be unconditionally compliant. Thus, this implementation maintains unconditional compliance with the specification though NPH support is not present.
The CGI specification is located at http://cgi-spec.golux.com.
|Modifier and Type||Class and Description|
Encapsulates the CGI environment and rules to derive that environment from the servlet container and request information.
Encapsulates the knowledge of how to run a CGI script, given the script's desired environment and (optionally) input/output streams Exposes a
This is an input stream specifically for reading HTTP headers.
|Constructor and Description|
|Modifier and Type||Method and Description|
Provides CGI Gateway service
Provides CGI Gateway service -- delegates to
Sets instance variables.
Prints out important Servlet API and container information Copied from SnoopAllServlet by Craig R.
doDelete, doHead, doOptions, doPut, doTrace, getLastModified, service, service
destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log
public void init(ServletConfig config) throws ServletException
Modified from Craig R. McClanahan's InvokerServlet
ServletConfigobject containing the servlet's configuration and initialization parameters
ServletException- if an exception has occurred that interferes with the servlet's normal operation
protected void printServletEnvironment(ServletOutputStream out, HttpServletRequest req, HttpServletResponse res) throws IOException
Copied from SnoopAllServlet by Craig R. McClanahan
out- ServletOutputStream as target of the information
req- HttpServletRequest object used as source of information
res- HttpServletResponse object currently not used but could provide future information
IOException- if a write operation exception occurs
protected void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException
protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException
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