$ENV perl equivalent in Java

Question

We are in our first steps in trying to convert some of our systems from Perl to Java.
In a module we had (Database module) which was responsible for all DB activity, we had an area where, upon errors, we printed out $ENV{SCRIPT_NAME} environment variable, which is set by Apache and can be read by Perl. This helps us debug things by knowing which script was ran when a DB error occurred.
As we are porting the Database module into a Database class, we are trying to think how we can achieve the same capability with Java.
I don't know of the existence of $ENV equivalent in Java. Not one that contains the web-server executed script, in case its a script that is ran by a web server.
Is there?
Note that the Database module may be ran as part of a Servelet but may also be part of just a simple server script. In perl, is such case, the $ENV{SCRIPT_NAME} would come out empty.
Any suggestions of how to do that?

Answer 1

Pidgin wrote:
As you indicated: Note that both are relatively slow and should only be used for exceptional or error conditions.
The access to the SCRIPT_NAME is actually a web re,ated variable that we need for showing which HTTP resquest generated the specific SQL error.It's only a variable in perl (or in CGI scripts, to be more precise).
It happens often enough, and doing a very low-level trace of the executed code migt not be the right option.SQLExceptions that need logging happen often? That shouldn't be the fact. How often?
Stacktraces are not awfully slow. They are ok for handling errors & exceptions. But they should not be used for classical flow control.
For example, it might be that the executing code is Script.class using Database.class, but Script.class can be initiated from www.whatever.com/script/ or www.whatever.com/premium/script/.. in each case, we want to know the full URL of the called "script'.With the stack trace you'd see the Servlet and/or Action that handles the request.
So we do need access to the web "environment".
What we do now, is store a static Servlet_Request variable (set on the first Database constructor, by passing the servlet request and response objects to the Database constructor). From that point on, we can access Servlet_Request.getRequestURI()That won't work as soon as more than one request is handled at the same time (which is very, very soon!).
You might want to look into something like log4js MDC, where you can at one point in your application set a key in a map and have that appear in every log statement from that thread until it's removed again.
This is quite different than the Perl logic, where we could access a "web enabled" System.getenv() and read from it SCRIPT_NAME or other web related parameters, if they existed (or returning null if they didn't)You should not try to apply the best practices learned by perl web programming 1:1 on Java. In the Java world pretty different concepts apply, especially when doing Web-Programming, as Perl web-applications are usually based on the rather antiquated CGI interface, while Java uses a central application server that handles each request as it wishes.