Question

In my webapp, I must use the context.xml to register a variable which is to be used in a JSP. For example, a variable X with the value "xfromcontext", so that I can print it in JSP as out.println(X). How do I get the X‘s value from context.xml?

Answer 1

You can specify an <Environment> entry which does exactly the same as regular <env-entry> in web.xml.

E.g.

<Environment name="X" value="xfromcontext" type="java.lang.String" />

which is obtainable (in servlet) by

String X = (String) new InitialContext().lookup("java:comp/env/X");
// ...

I’d suggest to read it once and store it in the application scope on webapp’s startup. You can use a ServletContextListener for this. Then you can just access it in JSP by ${X}. Doing a out.println() in JSP is a rather old school way which has been discouraged over a decade ago.