Head First Servlets and JSP, 2nd Edition

You can make the exception an attribute

In a real Java try/catch, the catch argument is the exception object. But with web app error handling, remember, only officially-designated error pages get the exception object. To any other page, the exception just isn’t there. So this does not work:

Using the “var” attribute in <c:catch>

Use the optional var attribute if you want to access the exception after the end of the <c:catch> tag. It puts the exception object into the page scope, under the name you declare as the value of var.

Note

Flow control works in a <c:catch> the way it does in a try block—NOTHING runs inside the <c:catch> body after the exception.

In a regular Java try/catch, once the exception occurs, the code BELOW that point in the try block never executes—control jumps directly to the catch block. With the <c:catch> tag, once the exception occurs, two things happen:

1. If you used the optional “var” attribute, the exception object is assigned to it.

2. Flow jumps to below the body of the <c:catch> tag.

Be careful about this. If you want to use the “var” exception object, you must wait until ...